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Cohort Profile
Cohort study profile: a cohort of Korean atomic bomb survivors and their offspring
Hamin Lee1orcid, Jin-Wu Nam2,3orcid, Mi Kyung Kim1orcid, Inah Kim4orcid, Yu-Mi Kim1orcid, Boyoung Park1,3orcid
Epidemiol Health 2024;46:e2024089.
DOI: https://doi.org/10.4178/epih.e2024089
Published online: November 18, 2024

1Department of Preventive Medicine, Hanyang University College of Medicine, Seoul, Korea

2Department of Life Science, Hanyang University College of Natural Sciences, Seoul, Korea

3Institute of Bioscience and Biotechnology, Hanyang University, Seoul, Korea

4Department of Occupational and Environmental Medicine, Hanyang University College of Medicine, Seoul, Korea

Correspondence: Boyoung Park, Department of Preventive Medicine, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea, E-mail: hayejine@hanmail.net
• Received: July 8, 2024   • Accepted: November 1, 2024

© 2024, Korean Society of Epidemiology

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • The Korean Atomic Bomb Survivor Cohort (K-ABC) study was designed to investigate the health impacts of atomic bomb exposure on Korean survivors and to explore whether these effects are passed down genetically to their descendants. This paper outlines the study’s design, data collection methods, baseline socio-demographic characteristics, exposure status, and disease prevalence among the participants, based on survey responses and health examinations. From 2020 to 2024, a total of 2,544 individuals, comprising 1,109 atomic bomb survivors (G1), 1,193 children of G1 (G2), and 242 grandchildren of G1 (G3), consented to participate in the study. Of these, 1,828 participants (659 in G1, 927 in G2, and 242 in G3) completed the survey and underwent health examinations, representing a participation rate of 71.9%. Exposure information was gathered using a questionnaire and verified through records from the Korean Red Cross and a handbook issued by the Japanese government. Disease prevalence was determined based on participants’ self-reported physician diagnoses. This study presents details about the K-ABC study and provides baseline data on the participants recruited. These data will be valuable for interpreting the results of future K-ABC studies.
Atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki in August 1945. These events significantly impacted the many Koreans residing in Japan, who had been sent there as conscripts or laborers in mines and factories, or who had moved there to earn a living. It is estimated that around 70,000 Koreans were affected by the atomic bombings. Of these, approximately 40,000 died due to the bombings, while about 23,000 survivors eventually returned to Korea [1,2].
Since 1950, cohorts of atomic bomb survivors, in utero survivors, and children of survivors have been established in Japan to study the health effects of atomic bomb radiation. The Life Span Study, which includes a cohort of atomic bomb survivors, has documented a significant association between exposure to atomic bomb radiation and a higher incidence of solid cancers [3].
Despite the growing body of evidence on the health effects of radiation exposure in directly exposed individuals, it remains unclear whether these effects are passed down to their offspring. Research involving the offspring of Japanese atomic bomb survivors found no link between parental radiation exposure and increased disease prevalence or de novo mutations in their children [4,5]. Conversely, several studies focusing on the Chernobyl disaster have observed elevated genome abnormality rates in the children of Chernobyl liquidators born post-accident, suggesting potential transgenerational transmission of radiation-induced genomic instability [6]. Nonetheless, other research indicates that the impact of transgenerational genetic effects is minimal [7]. As a result, the implications of abnormal genome frequencies on the health of offspring remain unclear.
In Korea, several cross-sectional studies have been conducted on atomic bomb survivors and their children [811]. However, the findings from these studies, along with earlier results from research on the offspring of Japanese atomic bomb survivors, have not been sufficient to determine the hereditary effects of radiation exposure. To address this gap, the Korean Atomic Bomb Survivor Cohort (K-ABC) was established to investigate whether the health of survivors and their descendants is linked to exposure to atomic bomb radiation and if there is a hereditary effect from survivors to their offspring. This study introduces the K-ABC by outlining the study design, data collection methods, baseline socio-demographic characteristics, disease prevalence, and overall health status.
Sample size
To estimate an adequate sample size, we set a 2-sided significance level of 95%, an 80% power, an exposed/unexposed ratio of 4, and a prevalence odds ratio ranging from 1.1 to 2.0 in increments of 0.1. Considering the predicted risk size of radiation exposure from the atomic bomb, the magnitude of the risk used to estimate the correlation between general risk factors, and the number of atomic bomb victims that could realistically be investigated, we determined that this study required more than 1,500 participants to accurately reflect the relationship between general risk factors and atomic bomb exposure. Additionally, for trio analysis, it was necessary to recruit 300 participants from the same household. Therefore, to thoroughly investigate the health effects on atomic bomb survivors and the heritability of atomic bomb exposure, at least 1,800 participants were needed for this study.
Study participants
The K-ABC includes three distinct groups: Korean atomic bomb survivors (G1), who are designated as “victims” under the Special Act on the Support for Korean Atomic Bomb Victims; “G2,” the second generation, which refers to the children of G1; and “G3,” the third generation, including the grandchildren of G1.
The recruitment process for participants in the K-ABC has been previously outlined [12]. Initially, postal mail containing research descriptions and consent forms was dispatched to 2,093 G1 and 2,422 G2 registered members of the Korea Atomic Bomb Casualty Association and the Korea Atomic Bomb Casualty Offspring Association in 2020. Out of these, 1,668 individuals from G1 and G2 (36.9%) returned the signed informed consent forms and were subsequently invited to participate in interviews and health examinations. Additionally, researchers visited health checkup sites designated for G1, which are provided annually by the Korean Red Cross to support the welfare of atomic bomb survivors, to encourage participation in the study. During the baseline survey, individuals from G1 and G2 were encouraged to involve other family members, including parents, siblings, and children, in the study. From 2020 to 2024, a total of 2,544 participants from G1, G2, and G3 were enrolled (1,109 G1, 1,193 G2, and 242 G3). All participants were required to provide consent for their data to be linked to the Statistics Korea mortality data, National Cancer Registry data, National Health Insurance Service data, and Red Cross data via their resident registration numbers. This consent was a mandatory condition for participation and was secured from all 2,544 participants. Of these, 1,828 individuals (659 in G1, 927 in G2, and 242 in G3) participated in both the survey and the health examination, representing a participation rate of 71.9%. If participants met the criteria for a trio as previously defined [12], various configurations of trios were established. Specifically, a complete trio consisted of a G1 participant, their spouse, and at least one of their biological children. Incomplete trios were formed in two scenarios: either a G1 participant or their spouse along with two or more of their biological children participated, or three or more G2 individuals with the same biological parents participated, with at least one being from G1. An internal control trio included a G2 participant, their spouse, and their biological children (G3).
Variables and measurement
All variables and measurements used in this cohort study are presented in Table 1. The survey items for K-ABC comprised face-to-face interviews, pedigree information, and health examinations. These examinations included anthropometric measurements, blood pressure assessments, blood tests, and urine tests. Whole genome sequencing was conducted on the constructed trios.

Questionnaires

The questionnaire encompassed a range of topics including demographic information, exposure to atomic bombs, current health status, diagnosed diseases, history of exposure to medical radiation, health behaviors, and women’s reproductive health. Table 1 presents the items included in the questionnaire. This questionnaire was aligned with other nationwide Korean studies, such as the Korean National Health and Nutrition Examination Survey [13] and the Korean Genome and Epidemiology Study [14]. Unique to the K-ABC, questions related to atomic bomb exposure were specifically directed at G1 individuals who had a history of exposure to medical radiation.

Pedigree

The majority of parents of G1 individuals were also exposed to the atomic bomb, and most parents of the surviving G1 and G2 individuals had passed away due to old age. Additionally, those who suffered severe after effects from the atomic bomb tended to die earlier. The G1 participants in this study were generally healthy individuals likely to have a longer lifespan, which could introduce survival bias into the results. To mitigate this bias, detailed pedigree information was collected for both living and deceased family members, including spouses. This information included vital status, cause of death, age at death, history of diagnosed diseases, age at diagnosis, year of birth, and exposure to the atomic bomb. Family members considered included first-degree relatives such as parents, siblings, and children. Furthermore, data on second-degree relatives were gathered, focusing on their vital status, cause of death, and age at death for both G1 and G2. Information about grandchildren was collected solely from G1 individuals, while G2 individuals provided details about their aunts and uncles.

Anthropometric measurements and laboratory tests

Height, weight, blood pressure, waist circumference, hip circumference, upper arm circumference, and calf circumference were measured using standardized tools. The assessment included blood and urine tests typically part of a general health examination, such as hemoglobin A1c, random glucose, total cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, creatinine, gamma-glutamyl transferase, cholesterol, urine protein, glucose, and occult blood. Additionally, the K-ABC featured unique tests including white blood cells with differential count, complete blood count, interleukin (IL)-6, IL-4, IL-10, tumor necrosis factor-α, C-reactive protein, erythrocyte sedimentation rate, and interferon-γ, aimed at evaluating immunological and hematopoiesis characteristics specific to K-ABC.

Whole-genome sequencing

Targeting participants who met the criteria for trios, next-generation sequencing was used to identify de novo mutations and estimate the genetic inheritance of atomic bomb exposure. De novo mutations were quantified using the Genome Analysis Toolkit developed by the Broad Institute [14]. Subtypes of de novo mutations include single-nucleotide variations, small insertions/deletions, structural variations, copy number alterations, and chromothripsis. Whole-genome sequencing and analysis were conducted on 400 subjects who met the selection criteria established for this study.
Indirect follow-up of the participants
Through the use of resident registration numbers from participants who provided informed consent, we linked the records of 2,544 participants with data from Statistics Korea mortality, the National Cancer Registry, and the National Health Insurance Service. The vital status and cause of death of individuals from 1992 to 2022 were ascertained using the Statistics Korea Mortality Database, which recorded 81 deaths during the study period. The National Cancer Registry supplied data on cancer prevalence and incidence from 1988 to 2021, identifying 324 individuals with a history of cancer. Medical usage data from 2002 to 2022 were obtained from the National Health Insurance Service, which operates within a single-payer, fee-for-service, and compulsory universal healthcare insurance system.
Direct follow-up of the participants
Changes in health behaviors, self-reported health, and disease development among participants and their first-degree relatives were assessed using follow-up questionnaires. The initial follow-up is scheduled for 2024 and will be conducted biennially in the future.
Statistical analysis
Of the 2,544 participants, 1,828 completed the survey; their baseline characteristics, survey responses, pedigrees, and health examinations were analyzed. All categorical variables are presented as frequencies and percentages, while all continuous variables are reported as means and standard deviations. The data were stratified by generation (G1, G2, and G3) for analysis. The chi-square test and Fisher’s exact test were employed to examine disease prevalence based on the survey data from atomic bomb survivors and their descendants. Statistical analyses were conducted using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA).
Ethics statement
The Institutional Review Board of Hanyang University College of Medicine (approval No. HYUIRB-202007-014-21) approved this study.
Baseline characteristics
The 2,544 participants comprised 659 G1, 927 G2, and 242 G3 patients (875 male and 953 female). The baseline characteristics of these 1,828 participants are detailed in Table 2. All individuals in G1 were aged 70 years or older. The most common age range in G2 was 50–59 years, representing 383 (41.3%) of the group. For G3, the predominant age group was 20–29 years, encompassing 90 (37.2%) of its members. A trend was observed where the level of education increased with each successive generation. Additionally, 95.6% of G1 and 84.1% of G2 were affiliated with the Korea Atomic Bomb Casualty Association and the Korea Atomic Bomb Casualty Offspring Association.
Data on the atomic bomb exposure of G1 individuals are shown in Table 3. Among these individuals, 50% could not recall their distance from the hypocenter at the time of the bombing. Consequently, we utilized secondary data from the Korean Red Cross and the Hibakusha Techo, a handbook issued by the Japanese government, to determine the variables for exposed place and distance from the hypocenter. Notably, 97.9% of G1 individuals were exposed in Hiroshima. At the time of the bombing, 44.2% of G1 individuals were within 2 km of the hypocenter, classified as “inner proximal” according to the Life Span Cohort of Japanese survivors. Additionally, 18.5% were located 2.1–2.5 km away, termed “outer proximal,” and 32.7% were 2.6–10.0 km away, defined as “distal” by the same cohort. Overall, 84.4% were directly exposed to an atomic bomb, and 8.2% were exposed in utero.
Table 4 presents the health behaviors of the participants, which include smoking and drinking status, subjective health status, exercise frequency, and sleep quality over the past month. Notably, a majority of the participants had never smoked, with 64.5% reporting as such. A comparison revealed that the prevalence of current smokers was higher in the second generation (17.2%) compared to other generations. In terms of drinking status, less than half of the participants were lifetime abstainers (45.0%), with the first generation showing the highest percentage of abstainers at 59.6%. Among the second generation smokers, 55.9% were current smokers. When assessing subjective health status, most participants reported having either moderate (34.2%) or poor (35.0%) health. The first generation reported the highest percentage of poor health at 47.3%. In contrast, the second generation had the highest percentage reporting moderate health (38.7%), and the third generation had the highest percentage reporting good health (38.4%). Regarding exercise frequency, the largest group consisted of individuals who did not engage in physical activity, accounting for 47.5% of responses. The first generation reported the highest frequency of daily exercise (24.0%), while the second and third generations most commonly reported exercising 3–4 times a week (21.7 and 16.9%, respectively). As for overall sleep quality, the response “good” was the most frequently selected by participants, at 49.6%, across all generations.
Table 5 shows the medical radiation exposure history of the participants. Participants reported an average of 17.6 X-ray exposures, making it the most common type of exposure. Interventional radiography had the lowest average exposure, at 3.3 times. The first generation recorded the highest percentage of medical exposure history, followed by the second and third generations. These generations were exposed to various types of medical radiation, including computed tomography, fluoroscopy, nuclear medicine tests, interventional radiography, and radiation therapy. Notably, the second generation had the highest exposure rates to radiography, including dental panoramic radiography and mammography, with average exposures of 7.5 times and 7.6 times, respectively.
Table 6 presents the prevalence of various diseases among participants, categorized by generation. The most common conditions identified in the K-ABC study include hypertension (32.9%), hyperlipidemia (32.2%), vertebral stenosis or disc herniation (30.6%), and cataracts (29.1%). In the G1 group, there was a significant prevalence of several diseases: hypertension, hyperlipidemia, stroke, heart attack/angina, osteoarthritis, rheumatoid arthritis, osteoporosis, vertebral stenosis or disc herniation, diabetes mellitus, benign thyroid disease, cancer, dementia, cataracts, glaucoma, hearing loss, and prostate disease. Conversely, G2 individuals showed a notably high incidence of female infertility, uterine myoma, and vasectomy. In G3, diseases such as atopy and allergic rhinitis were particularly prevalent.
Table 7 shows the exposure data for 26,712 family members of the 1,828 study participants, as collected from the pedigree questionnaire. The data includes information on 10,407 family members from the G1 pedigree, 15,189 from the G2 pedigree, and 1,116 from the G3 pedigree. From this pedigree information, we were able to identify 4,887 individuals from G1, 7,555 from G2, and 5,222 from G3, including both deceased and living members. Regarding exposure to the atomic bomb, 94.8% of G1 fathers and 95.7% of G1 mothers were affected, with over 99% of these individuals subsequently passing away. In G2, 51.7% of fathers and 67.1% of mothers experienced exposure, with mortality rates of 65.4% for fathers and 30.4% for mothers, respectively. Among the siblings in G1 and G2, 57.6% and 8.4%, respectively, were directly exposed to the atomic bomb. The corresponding mortality rates were 41.4% for G1 siblings and 12.9% for G2 siblings.
This study has the following strengths: First, previous studies of Korean atomic bomb survivors were cross-sectional studies. This is the first cohort study of Korean atomic bomb survivors that collected biospecimens and obtained informed consent for linking different secondary data sources from various organizations, contributing to complete follow-up. Through both direct and indirect follow-ups, long-term health status and disease development can be monitored as the participants age.
Second, this is the first whole-genome study involving a substantial number of atomic bomb survivor trios. Earlier whole-genome studies on atomic bomb survivors and their children, conducted in Japan, included only three trios, an insufficient number to identify any association [5]. Whole-genome sequencing has the potential to reveal direct biological mechanisms underlying the heritability of atomic bomb exposure.
This study has the following limitations: First, several G2 or G3 individuals were unaware that they were offspring of atomic bomb survivors because G1 individuals concealed their exposure from their families due to concerns regarding the stigmatization of their stay in Japan during the colonial era. Additionally, atomic bomb survivors and their descendants who did not possess a Hibakusha Techo or were not registered with the Korea Red Cross or Casualty Association were excluded from this study due to the absence of documentation verifying their exposure status.
Second, individuals who died immediately after exposure to the atomic bombs or before the establishment of this cohort study could not be included. This may have led to survival bias. To adjust for this potential bias, the K-ABC obtained pedigree information, including individuals who had already died. Thus, it was possible to examine the effects of atomic-bomb exposure on disease and mortality.
Third, there may have been information bias regarding the exposure of G1 individuals to atomic bombs and their disease history. Since most G1 participants were exposed at a very young age, the accuracy of their recollections may be compromised. To minimize this bias, we linked our data with records from Hibakusha Techo and the Korean Red Cross, which provided more precise information about the locations and distances of exposure. However, concerns about information bias for other exposure-related items persist. Similarly, the majority of G1 participants were too young at the time of exposure to remember specific details such as the diseases diagnosed or the dates of diagnosis. To address this limitation, we attempted to link our data with information from the National Cancer Registry and the National Health Insurance Service. However, data from the National Health Insurance Service are only available from 2002, and National Cancer Registry data from 1988 onward. Consequently, any diseases diagnosed before these years could not be captured in our study. Therefore, information regarding the deaths of individuals is required as an alternative indicator of their overall disease status.
This cohort study will continue to monitor the occurrence of death and disease to identify relevant health conditions. Additionally, individuals who did not participate in the study but were included in the pedigree were also tracked to confirm any instances of disease or death.
This study offers insights into the K-ABC study and provides baseline data for the participants recruited. These data could be useful for interpreting results in future K-ABC studies.

DATA ACCESSIBILITY

The datasets used during the current study are available from the corresponding author upon reasonable request.

Conflict of interest

The authors have no conflicts of interest to declare for this study.

Funding

This study was supported by a grant from the Division of Disease Control Policy, Ministry of Health and Welfare, Republic of Korea (No. 00238224400).

Author contributions

Conceptualization: Park B. Data curation: Lee H. Formal analysis: Lee H. Funding acquisition: Park B, Nam JW, Kim MK, Kim I, Kim YM. Methodology: Park B. Project administration: Park B, Nam JW. Writing – original draft: Lee H. Writing – review & editing: Lee H, Park B, Nam JW, Kim MK, Kim I, Kim YM.

We thank all the participants and researchers, especially Yunja Han, Eun Hee Yu, the Korea Atomic Bomb Casualty Association, and the Korea Atomic Bomb Casualty Offspring Association.
Table 1
Questionnaires and measurements used in the Korean Atomic Bomb Survivors Cohort
Generation No. of items Sample (n) Components
Questionnaire 1 273 1,828 Sex, age, association registration status, residential area, family member, marital status, average household income, education; atomic bomb exposure information: hibakusha, place of exposure, distance from the hypocenter, shielding, symptoms after exposure, long-term sequelae; Health status: subjective health, diagnosed diseases; Medical radiation exposure history: X-rays, dental panoramic X-rays, computed tomography, fluoroscopy, mammography, interventional radiography, radiation therapy; Fracture, alcohol consumption, lifetime tobacco smoking, physical activity, sleep duration and quality, nutritional assessment; Reproductive factors: menopausal status, age at menarche, age at first pregnancy, number of delivery experiences, age at first and last deliveries, duration of breastfeeding, age at first breastfeeding, no. of artificial abortions, age at first artificial abortion, hysterectomy history
2 271
3 270
Pedigree 1 62 1,828 Birth year, vital status, year of death, cause of death, disease history, age at diagnosis, and atomic bomb exposure status of first-degree family (parents, siblings, and children), second-degree family (aunt, uncle, and grandchildren), and spouse; Questions asked to first generation regarding the second-degree family included those on grandchildren; Questions for the second generation regarding second-degree family included those on aunts and uncles; The third generation were not asked any questions regarding second-degree family
2 62
3 45
Anthropometric 1, 2, 3 11 1,828 Height, weight, waist circumference, hip circumference, upper arm circumference, calf circumference, and blood pressure
Blood examination 1, 2, 3 20 1,784 Random glucose, hemoglobin A1c, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, complete blood count, creatinine, blood urea nitrogen, total cholesterol, triglycerides, high-density lipoprotein, and cholesterol
Urine examination 1, 2, 3 10 1,703 pH, nitrate, specific gravity, protein, glucose, ketones, bilirubin, occult blood, urobilinogen, and leukocyte esterase
Whole genome sequencing Trio (complete, incomplete, and internal trios) Genome Analysis Toolkit
Table 2
Baseline socio-demographic characteristics of participants of the Korean Atomic Bomb Survivors Cohort by generation
Characteristics Total (n=1,828) Generation
First (n=659) Second (n=927) Third (n=242)
Age (yr)
 <20 58 (3.2) 0 (0.0) 0 (0.0) 58 (24.0)
 20–29 90 (4.9) 0 (0.0) 0 (0.0) 90 (37.2)
 30–39 67 (3.7) 0 (0.0) 6 (0.6) 61 (25.2)
 40–49 191 (10.4) 0 (0.0) 164 (17.7) 27 (11.2)
 50–59 389 (21.3) 0 (0.0) 383 (41.3) 6 (2.5)
 60–69 280 (15.3) 0 (0.0) 280 (30.2) 0 (0.0)
 70–79 376 (20.6) 282 (42.8) 94 (10.1) 0 (0.0)
 ≥80 377 (20.6) 377 (55.2) 0 (0.0) 0 (0.0)
Sex
 Male 875 (47.9) 327 (49.6) 428 (46.2) 120 (49.6)
 Female 953 (52.1) 332 (50.4) 499 (53.8) 122 (50.4)
Marital status
 Single 280 (15.3) 0 (0.0) 84 (9.1) 196 (81.0)
 Married 1,036 (56.7) 327 (49.6) 673 (72.6) 36 (14.9)
 Widowed 319 (17.5) 269 (40.8) 50 (5.4) 0 (0.0)
 Separated/Divorced 158 (8.6) 32 (4.9) 117 (12.6) 9 (3.7)
 Missing data 35 (1.9) 31 (4.7) 3 (0.3) 1 (0.4)
Education
 Illiterate 127 (6.9) 116 (17.6) 10 (1.1) 1 (0.4)
 Primary school1 390 (21.3) 259 (39.3) 106 (11.4) 25 (10.3)
 Secondary school 200 (10.9) 97 (14.7) 90 (9.7) 13 (5.4)
 High school 461 (25.2) 103 (15.6) 317 (34.2) 41 (16.9)
 College or more 614 (33.6) 53 (8.0) 400 (43.1) 161 (66.5)
 Missing data 36 (2.0) 31 (4.7) 4 (0.4) 1 (0.4)
Registry with the Korea Atomic Bomb Casualty Association
 Registered 1,410 (77.1) 630 (95.6) 780 (84.1) 0 (0.0)
 Not registered 176 (9.6) 29 (4.4) 147 (15.9) 242 (100)
Average household income (104 Korean won/mo)
 <100 478 (26.1) 347 (52.7) 121 (13.1) 0 (0.0)
 100–299 392 (21.4) 119 (18.1) 235 (25.4) 38 (15.7)
 300–499 260 (14.2) 21 (3.2) 195 (21.0) 44 (18.2)
 ≥500 359 (19.6) 8 (1.2) 283 (30.5) 68 (28.1)
 Do not know 339 (18.5) 164 (24.9) 93 (10.0) 82 (33.9)
National basic livelihood security beneficiary
 Yes 95 (5.2) 52 (7.9) 39 (4.2) 4 (1.7)
 No 1,703 (93.2) 588 (89.2) 882 (95.1) 233 (96.3)
 Do not know 24 (1.3) 17 (2.6) 4 (0.4) 3 (1.2)
 Missing data 6 (0.3) 2 (0.3) 2 (0.2) 2 (0.8)
Residential area
 Seoul/Gyeonggi-do/Incheon 480 (26.3) 161 (24.4) 231 (24.9) 88 (36.4)
 Busan/Gyeongsangnam-do 962 (52.6) 400 (60.7) 467 (50.4) 95 (39.3)
 Deagu/Gyeongsangbuk-do 270 (14.8) 61 (9.3) 167 (18.0) 42 (17.4)
 Others 92 (5.0) 20 (3.0) 55 (5.9) 17 (7.0)
 Missing data 24 (1.3) 17 (2.6) 7 (0.8) 0 (0.0)

Values are presented as number (%).

1 Seodang (a traditional village school in Korea) is categorized as “primary school.”

Table 3
Atomic bomb exposure of first-generation individuals in the Korean Atomic Bomb Survivors Cohort (n=659)
Variables n (%)
Exposed place
 Hiroshima 645 (97.9)
 Nagasaki 14 (2.1)
Distance from hypocenter (km)
 0.0–0.5 0 (0.0)
 0.6–1.0 14 (2.1)
 1.1–1.5 96 (14.6)
 1.6–2.0 181 (27.5)
 2.1–2.5 122 (18.5)
 2.6–3.0 106 (16.1)
 3.1–3.5 40 (6.1)
 ≥3.6 69 (10.5)
 Missing data 31 (4.7)
Exposure type
 Direct exposure 556 (84.4)
 Intrauterine exposure 54 (8.2)
 Entered the city within 2 wk of the bombing 2 (0.3)
 Others 1 (0.2)
 Missing data 46 (7.0)
Presence of a radiation shield
 None 36 (5.5)
 Partial 101 (15.3)
 Full 352 (53.4)
 Others 2 (0.3)
 Missing data 168 (24.5)
Reason for visiting Japan
 Residence 500 (75.9)
 Following parents or relatives 77 (11.7)
 Others 50 (7.6)
 Missing data 32 (4.9)
Symptoms of aftereffects of atomic bomb exposure
 Had aftereffect symptoms 193 (29.3)
 Did not have aftereffect symptoms 134 (20.3)
 Do not know 302 (45.8)
 Missing data 30 (4.6)
Use of medical care due to aftereffects of atomic bomb exposure
 Used 137 (20.8)
 Did not use 306 (46.4)
 Missing data 216 (32.8)
Table 4
Baseline health behaviors, including smoking and drinking, of participants in the Korean Atomic Bomb Survivors Cohort
Variables Total (n=1,828) Generation
First (n=659) Second (n=927) Third (n=242)
Smoking status
 Never smoker 1,179 (64.5) 429 (65.1) 555 (59.9) 195 (80.6)
 Former smoker 408 (22.3) 186 (28.2) 213 (23.0) 9 (3.7)
 Current smoker 240 (13.1) 44 (6.7) 159 (17.2) 37 (15.3)
 Missing 1 (0.1) 0 (0.0) 0 (0.0) 1 (0.4)
Drinking status
 Lifetime abstainer 823 (45.0) 393 (59.6) 331 (35.7) 99 (40.9)
 Former drinker 196 (10.7) 108 (16.4) 77 (8.3) 11 (4.6)
 Current drinker 805 (44.0) 156 (23.7) 518 (55.9) 131 (54.1)
 Missing 4 (0.2) 2 (0.3) 1 (0.1) 1 (0.4)
Health status
 Very good 65 (3.6) 16 (2.4) 20 (2.2) 29 (12.0)
 Good 372 (20.4) 82 (12.4) 197 (21.3) 93 (38.4)
 Moderate 625 (34.2) 176 (26.7) 359 (38.7) 90 (37.2)
 Bad 640 (35.0) 312 (47.3) 299 (32.3) 29 (12.0)
 Very bad 125 (6.8) 73 (11.1) 51 (5.5) 1 (0.4)
 Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
Exercise frequency (times/wk)
 Never 868 (47.5) 353 (53.6) 386 (41.6) 129 (53.3)
 1–2 178 (9.7) 20 (3.0) 123 (13.3) 35 (14.5)
 3–4 322 (17.6) 80 (12.1) 201 (21.7) 41 (16.9)
 4–6 148 (8.1) 47 (7.1) 83 (9.0) 18 (7.4)
 Everyday 311 (17.0) 158 (24.0) 134 (14.5) 19 (7.9)
 Missing 1 (0.1) 0 (0.0) 0 (0.0) 0 (0.0)
Sleep quality over the past month
 Very good 204 (11.2) 70 (10.6) 84 (9.1) 50 (20.7)
 Good 907 (49.6) 304 (46.1) 477 (51.5) 126 (52.1)
 Bad 565 (30.9) 200 (30.4) 303 (32.7) 62 (25.6)
 Very bad 116 (6.4) 55 (8.4) 57 (6.2) 4 (1.7)
 Missing 36 (2.0) 30 (4.6) 6 (0.7) 0 (0.0)

Values are presented as number (%).

Table 5
Baseline medical radiation exposure history of participants and their offspring by generation of the Korean Atomic Bomb Survivors Cohort
Variable Total (n=1,828) Generation
First (n=659) Second (n=927) Third (n=242)
X-rays
 Never been exposed 67 (3.7) 32 (4.9) 15 (1.6) 20 (8.3)
 Do not know 559 (30.6) 300 (45.5) 228 (24.6) 31 (12.8)
 Missing 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
 Exposed 1,202 (65.8) 327 (49.6) 684 (73.8) 191 (78.9)
  Mean±SD 17.6±12.9 21.1±13.1 18.0±12.7 10.2±10.0
Dental panoramic X-rays
 Never been exposed 190 (10.4) 95 (14.4) 69 (7.4) 26 (10.7)
 Do not know 441 (24.1) 263 (39.9) 152 (16.4) 26 (10.7)
 Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
 Exposed 1,196 (65.4) 301 (45.7) 705 (76.1) 190 (78.5)
  Mean±SD 7.9±6.8 10.7±7.9 7.5±6.4 4.9±4.4
Computed tomography
 Never been exposed 433 (23.7) 71 (10.8) 236 (25.5) 126 (52.1)
 Do not know 396 (21.7) 283 (42.9) 99 (10.7) 14 (5.8)
 Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
 Exposed 998 (54.6) 305 (46.3) 591 (63.8) 102 (42.2)
  Mean±SD 6.1±6.7 11.2±7.9 4.2±4.8 2.2±2.0
Fluoroscopy
 Never been exposed 1,098 (60.1) 345 (52.4) 551 (59.4) 202 (83.5)
 Do not know 209 (31.7) 65 (7.0) 10 (4.1) 284 (15.5)
 Missing 2 (0.3) 1 (0.2) 0 (0.0) 3 (0.2)
 Exposed 443 (24.2) 103 (15.6) 310 (33.4) 30 (12.4)
  Mean±SD 4.6±6.8 8.3±11.2 3.6±4.4 2.2±2.5
Nuclear medicine test - oral and intravenous administration of radiopharmaceuticals (bone scan, thyroid scan, PET-CT, SPECT, etc.)
 Never been exposed 1,620 (88.6) 536 (81.3) 851 (91.8) 233 (96.3)
 Do not know 141 (7.7) 99 (15.0) 34 (3.7) 8 (3.3)
 Missing 1 (0.1) 0 (0.0) 1 (0.2) 0 (0.0)
 Exposed 66 (3.6) 24 (3.6) 41 (4.4) 1 (0.4)
  Mean±SD 5.5±10.3 8.3±16.1 3.8±4.0 8.0±.0.0
Nuclear medicine test - oral and intravenous administration of radiopharmaceuticals (thyroid radioiodine therapy, strontium-89 bone metastasis treatment, etc.)
 Never been exposed 1,677 (91.7) 556 (84.4) 886 (95.6) 235 (97.1)
 Do not know 130 (7.1) 94 (14.3) 31 (3.3) 5 (2.1)
 Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
 Exposed 20 (1.1) 9 (1.4) 9 (1.0) 2 (0.8)
  Mean±SD 6.3±17.5 11.8±25.7 1.6±1.3 2.5±2.1
Mammography
 Never been exposed 1,002 (54.8) 342 (51.9) 457 (49.3) 203 (83.9)
 Do not know 277 (15.2) 171 (26.0) 101 (10.9) 5 (2.1)
 Missing 3 (0.2) 0 (0.0) 3 (0.3) 0 (0.0)
 Exposed 546 (29.9) 146 (22.2) 366 (39.5) 34 (14.1)
  Mean±SD 8.5±6.4 12.1±7.2 7.6±5.5 3.1±2.6
Interventional radiography
 Never been exposed 1,668 (91.3) 559 (84.8) 872 (94.1) 237 (97.9)
 Do not know 102 (5.6) 77 (11.7) 20 (2.2) 5 (2.1)
 Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
 Exposed 57 (3.1) 23 (3.5) 34 (3.7) 0 (0.0)
  Mean±SD 3.3±10.5 5.9±16.3 1.5±1.1 0.0±0.0
Radiation therapy
 Never been exposed 1,686 (92.2) 566 (85.9) 884 (95.4) 236 (97.5)
 Do not know 93 (5.1) 72 (10.9) 16 (1.7) 5 (2.1)
 Missing 3 (0.2) 1 (0.2) 2 (0.2) 0 (0.0)
 Exposed 46 (2.5) 20 (3.0) 25 (2.7) 1 (0.4)
  Mean±SD 17.9±22.2 15.8±20.1 20.3±24.1 1.0±0.0

Values are presented as number (%).

SD, standard deviation; PET-CT, position emission tomography-computed tomography; SPECT, single-photon emission computed tomography.

Table 6
Disease prevalence among the participants in the Korean Atomic Bomb Survivors Cohort by generation
Variables Total (n=1,828) Generation χ2 (p-value)
First (n=659) Second (n=927) Third (n=242)
Malformations (such as those in the heart and fingers among others) 24 (1.3) 6 (0.9) 12 (1.3) 6 (2.5) 0.186
Cerebral palsy 3 (0.2) 0 (0.0) 3 (0.3) 0 (0.0) 0.379
Hypertension 601 (32.9) 367 (55.7) 230 (24.8) 4 (1.7) <0.001
Hyperlipidemia 589 (32.2) 274 (41.6) 305 (32.9) 10 (4.1) <0.001
Stroke 78 (4.3) 53 (8.0) 24 (2.6) 1 (0.4) <0.001
Heart attack/angina 113 (6.2) 83 (12.6) 30 (3.2) 0 (0.0) <0.001
Osteoarthritis 308 (16.8) 182 (27.6) 124 (13.4) 2 (0.8) <0.001
Rheumatoid arthritis 74 (4.0) 35 (5.3) 37 (4.0) 2 (0.8) 0.010
Osteoporosis 287 (15.7) 190 (28.8) 97 (10.5) 0 (0.0) <0.001
Vertebral stenosis or disc herniation 559 (30.6) 252 (38.2) 285 (30.7) 22 (9.1) <0.001
Diabetes mellitus 324 (17.7) 195 (29.6) 125 (13.5) 4 (1.7) <0.001
Benign thyroid disease 212 (11.6) 95 (14.4) 109 (11.8) 8 (3.3) <0.001
Cancer 198 (10.8) 110 (16.7) 85 (9.2) 3 (1.2) <0.001
Major depressive disorder 130 (7.1) 55 (8.3) 64 (6.9) 11 (4.5) 0.136
Parkinson’s disease 8 (0.4) 5 (0.8) 3 (0.3) 0 (0.0) 0.309
Epilepsy 4 (0.2) 0 (0.0) 4 (0.4) 0 (0.0) 0.195
Intellectual disability 14 (0.8) 0 (0.0) 10 (1.1) 4 (1.7) 0.003
Peripheral neuropathy 11 (0.6) 6 (0.9) 5 (0.5) 0 (0.0) 0.366
Schizophrenia 4 (0.2) 1 (0.2) 3 (0.3) 0 (0.0) 0.799
Dementia 50 (2.7) 47 (7.1) 3 (0.3) 0 (0.0) <0.001
Atopy 100 (5.5) 24 (3.6) 42 (4.5) 34 (14.0) <0.001
Alopecia 85 (4.6) 20 (3.0) 52 (5.6) 13 (5.4) 0.048
Allergy 178 (9.7) 44 (6.7) 111 (12.0) 23 (9.5) 0.002
Allergic rhinitis 273 (14.9) 43 (6.5) 151 (16.3) 79 (32.6) <0.001
Asthma 87 (4.8) 38 (5.8) 40 (4.3) 9 (3.7) 0.293
Cataract 532 (29.1) 380 (57.7) 151 (16.3) 1 (0.4) <0.001
Glaucoma 62 (3.4) 39 (5.9) 23 (2.5) 0 (0.0) <0.001
Macular degeneration 32 (1.8) 18 (2.7) 12 (4.3) 2 (0.8) 0.062
Hearing loss 113 (6.2) 71 (10.8) 40 (4.3) 3 (1.2) <0.001
Meniere’s disease 14 (0.8) 2 (0.3) 10 (1.1) 2 (0.8) 0.210
Male infertility 4 (0.5) 2 (0.6) 2 (0.5) 0 (0.0) 1.000
Prostate disease 228 (26.6) 166 (53.4) 60 (14.1) 2 (1.7) <0.001
Vasectomy 96 (11.2) 9 (2.9) 85 (19.9) 2 (1.7) <0.001
Female infertility 18 (1.9) 1 (0.3) 17 (3.4) 0 (0.0) <0.001
Uterine myoma 193 (20.6) 44 (13.8) 140 (28.2) 9 (7.4) <0.001
Tubal ligation 41 (4.4) 16 (5.0) 25 (5.0) 0 (0.0) 0.014
Pain of unknown origin 175 (9.6) 56 (8.5) 103 (11.1) 16 (6.6) 0.053
Other diseases 587 (32.1) 196 (29.7) 338 (36.5) 53 (21.9) <0.001

Values are presented as number (%).

Table 7
Atomic bomb exposure and vital statistics of family members reported by participants in the Korean Atomic Bomb Survivors Cohort, by generation
Variable Total Generation
First Second Third
Subtotal 26,712 (100) 10,407 (100) 15,189 (100) 1,116 (100)
 Family member’s generation
  First 4,887 (18.3) 3,505 (33.7) 1,382 (9.1) 0 (0.0)
  Second 7,555 (28.3) 3,335 (32.1) 3,973 (26.2) 247 (22.1)
  Third 5,222 (19.6) 2,873 (27.6) 1,821 (12.0) 528 (47.3)
  Fourth 66 (0.2) 0 (0.0) 0 (0.0) 66 (5.9)
  Not exposed 8,904 (33.3) 645 (6.2) 7,984 (52.6) 275 (24.6)
  Do not know 78 (0.3) 49 (0.5) 29 (0.2) 0 (0.0)
 Sex
  Male 13,255 (49.6) 5,213 (50.1) 7,489 (49.3) 553 (49.6)
  Female 13,187 (49.4) 5,106 (49.1) 7,524 (49.5) 557 (49.9)
  Do not know 270 (1.0) 88 (0.9) 176 (1.2) 6 (0.5)
 Survival status
  Alive 18,921 (70.8) 7,527 (72.3) 10,307 (67.9) 1,087 (97.4)
  Dead 7,524 (28.2) 2,804 (26.9) 4,697 (30.9) 23 (2.1)
  Miscarriage 233 (0.9) 60 (0.6) 167 (1.1) 6 (0.5)
  Stillbirth 8 (0.0) 6 (0.1) 2 (0.0) 0 (0.0)
  Do not know 26 (0.1) 10 (0.1) 16 (0.1) 0 (0.0)
Father 1,797 (100) 630 (100) 924 (100) 241 (100)
 Exposed history
  Directly exposed 1,075 (59.9) 597 (94.8) 478 (51.7) 0 (0.0)
  Indirectly exposed 88 (4.9) 0 (0.0) 0 (0.0) 88 (36.5)
  Not exposed 609 (33.9) 21 (3.3) 435 (47.1) 153 (63.5)
  Do not know 20 (1.1) 10 (1.6) 10 (1.1) 0 (0.0)
  Missing 3 (0.2) 2 (0.3) 1 (0.1) 0 (0.0)
 Survival status
  Alive 546 (30.4) 3 (0.5) 320 (34.6) 223 (92.5)
  Dead 1,249 (69.6) 627 (99.5) 604 (65.4) 18 (7.5)
Mother 1,795 (100) 630 (100) 924 (100) 241 (100)
 Exposure history
  Directly exposed 1,223 (68.1) 603 (95.7) 620 (67.1) 0 (0.0)
  Indirectly exposed 160 (8.9) 0 (0.0) 1 (0.1) 159 (66.0)
  Not exposed 396 (22.1) 14 (2.2) 300 (32.5) 82 (34.0)
  Do not know 14 (0.8) 11 (1.8) 3 (0.3) 0 (0.0)
  Missing 2 (0.1) 2 (0.3) 0 (0.0) 0 (0.0)
 Survival status
  Alive 885 (49.3) 4 (0.6) 643 (69.6) 238 (98.8)
  Dead 910 (50.7) 626 (99.4) 281 (30.4) 3 (1.2)
Brothers and sisters 6,463 (100) 2851 (100) 3326 (100) 286 (100)
 Exposure history
  Directly exposed 1,921 (29.7) 1,643 (57.6) 278 (8.4) 0 (0.0)
  Indirectly exposed 4,438 (68.7) 1,133 (39.7) 3,020 (90.8) 286 (100)
  Not exposed 72 (1.1) 59 (2.1) 13 (0.4) 0 (0.0)
  Do not know 31 (0.5) 16 (0.6) 15 (0.5) 0 (0.0)
 Survival status
  Alive 4,838 (74.9) 1,661 (58.3) 2,893 (87.0) 284 (99.3)
  Dead 1,612 (24.9) 1,181 (41.4) 429 (12.9) 2 (0.7)
  Do not know 13 (0.2) 9 (0.3) 4 (0.1) 0 (0.0)
Children 4,087 (100) 2,188 (100) 1,833 (100) 66 (100)
 Exposure history
  Directly exposed 1 (0.0) 1 (0.0) 0 (0.0) 0 (0.0)
  Indirectly exposed 4,085 (99.9) 2,186 (99.9) 1,833 (100) 66 (100)
  Not exposed 1 (0.0) 1 (0.0) 0 (0.0) 0 (0.0)
  Survival status
 Alive 3,695 (90.4) 2,003 (91.5) 1,632 (89.0) 60 (90.9)
  Dead 151 (3.7) 119 (5.4) 32 (1.8) 0 (0.0)
  Miscarriage 233 (5.7) 60 (2.7) 167 (9.1) 6 (9.1)
  Stillbirth 8 (0.2) 6 (0.3) 2 (0.1) 0 (0.0)

Values are presented as number (%).

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Figure & Data

References

    Citations

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      Cohort study profile: a cohort of Korean atomic bomb survivors and their offspring
      Cohort study profile: a cohort of Korean atomic bomb survivors and their offspring
      Generation No. of items Sample (n) Components
      Questionnaire 1 273 1,828 Sex, age, association registration status, residential area, family member, marital status, average household income, education; atomic bomb exposure information: hibakusha, place of exposure, distance from the hypocenter, shielding, symptoms after exposure, long-term sequelae; Health status: subjective health, diagnosed diseases; Medical radiation exposure history: X-rays, dental panoramic X-rays, computed tomography, fluoroscopy, mammography, interventional radiography, radiation therapy; Fracture, alcohol consumption, lifetime tobacco smoking, physical activity, sleep duration and quality, nutritional assessment; Reproductive factors: menopausal status, age at menarche, age at first pregnancy, number of delivery experiences, age at first and last deliveries, duration of breastfeeding, age at first breastfeeding, no. of artificial abortions, age at first artificial abortion, hysterectomy history
      2 271
      3 270
      Pedigree 1 62 1,828 Birth year, vital status, year of death, cause of death, disease history, age at diagnosis, and atomic bomb exposure status of first-degree family (parents, siblings, and children), second-degree family (aunt, uncle, and grandchildren), and spouse; Questions asked to first generation regarding the second-degree family included those on grandchildren; Questions for the second generation regarding second-degree family included those on aunts and uncles; The third generation were not asked any questions regarding second-degree family
      2 62
      3 45
      Anthropometric 1, 2, 3 11 1,828 Height, weight, waist circumference, hip circumference, upper arm circumference, calf circumference, and blood pressure
      Blood examination 1, 2, 3 20 1,784 Random glucose, hemoglobin A1c, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, complete blood count, creatinine, blood urea nitrogen, total cholesterol, triglycerides, high-density lipoprotein, and cholesterol
      Urine examination 1, 2, 3 10 1,703 pH, nitrate, specific gravity, protein, glucose, ketones, bilirubin, occult blood, urobilinogen, and leukocyte esterase
      Whole genome sequencing Trio (complete, incomplete, and internal trios) Genome Analysis Toolkit
      Characteristics Total (n=1,828) Generation
      First (n=659) Second (n=927) Third (n=242)
      Age (yr)
       <20 58 (3.2) 0 (0.0) 0 (0.0) 58 (24.0)
       20–29 90 (4.9) 0 (0.0) 0 (0.0) 90 (37.2)
       30–39 67 (3.7) 0 (0.0) 6 (0.6) 61 (25.2)
       40–49 191 (10.4) 0 (0.0) 164 (17.7) 27 (11.2)
       50–59 389 (21.3) 0 (0.0) 383 (41.3) 6 (2.5)
       60–69 280 (15.3) 0 (0.0) 280 (30.2) 0 (0.0)
       70–79 376 (20.6) 282 (42.8) 94 (10.1) 0 (0.0)
       ≥80 377 (20.6) 377 (55.2) 0 (0.0) 0 (0.0)
      Sex
       Male 875 (47.9) 327 (49.6) 428 (46.2) 120 (49.6)
       Female 953 (52.1) 332 (50.4) 499 (53.8) 122 (50.4)
      Marital status
       Single 280 (15.3) 0 (0.0) 84 (9.1) 196 (81.0)
       Married 1,036 (56.7) 327 (49.6) 673 (72.6) 36 (14.9)
       Widowed 319 (17.5) 269 (40.8) 50 (5.4) 0 (0.0)
       Separated/Divorced 158 (8.6) 32 (4.9) 117 (12.6) 9 (3.7)
       Missing data 35 (1.9) 31 (4.7) 3 (0.3) 1 (0.4)
      Education
       Illiterate 127 (6.9) 116 (17.6) 10 (1.1) 1 (0.4)
       Primary school1 390 (21.3) 259 (39.3) 106 (11.4) 25 (10.3)
       Secondary school 200 (10.9) 97 (14.7) 90 (9.7) 13 (5.4)
       High school 461 (25.2) 103 (15.6) 317 (34.2) 41 (16.9)
       College or more 614 (33.6) 53 (8.0) 400 (43.1) 161 (66.5)
       Missing data 36 (2.0) 31 (4.7) 4 (0.4) 1 (0.4)
      Registry with the Korea Atomic Bomb Casualty Association
       Registered 1,410 (77.1) 630 (95.6) 780 (84.1) 0 (0.0)
       Not registered 176 (9.6) 29 (4.4) 147 (15.9) 242 (100)
      Average household income (104 Korean won/mo)
       <100 478 (26.1) 347 (52.7) 121 (13.1) 0 (0.0)
       100–299 392 (21.4) 119 (18.1) 235 (25.4) 38 (15.7)
       300–499 260 (14.2) 21 (3.2) 195 (21.0) 44 (18.2)
       ≥500 359 (19.6) 8 (1.2) 283 (30.5) 68 (28.1)
       Do not know 339 (18.5) 164 (24.9) 93 (10.0) 82 (33.9)
      National basic livelihood security beneficiary
       Yes 95 (5.2) 52 (7.9) 39 (4.2) 4 (1.7)
       No 1,703 (93.2) 588 (89.2) 882 (95.1) 233 (96.3)
       Do not know 24 (1.3) 17 (2.6) 4 (0.4) 3 (1.2)
       Missing data 6 (0.3) 2 (0.3) 2 (0.2) 2 (0.8)
      Residential area
       Seoul/Gyeonggi-do/Incheon 480 (26.3) 161 (24.4) 231 (24.9) 88 (36.4)
       Busan/Gyeongsangnam-do 962 (52.6) 400 (60.7) 467 (50.4) 95 (39.3)
       Deagu/Gyeongsangbuk-do 270 (14.8) 61 (9.3) 167 (18.0) 42 (17.4)
       Others 92 (5.0) 20 (3.0) 55 (5.9) 17 (7.0)
       Missing data 24 (1.3) 17 (2.6) 7 (0.8) 0 (0.0)
      Variables n (%)
      Exposed place
       Hiroshima 645 (97.9)
       Nagasaki 14 (2.1)
      Distance from hypocenter (km)
       0.0–0.5 0 (0.0)
       0.6–1.0 14 (2.1)
       1.1–1.5 96 (14.6)
       1.6–2.0 181 (27.5)
       2.1–2.5 122 (18.5)
       2.6–3.0 106 (16.1)
       3.1–3.5 40 (6.1)
       ≥3.6 69 (10.5)
       Missing data 31 (4.7)
      Exposure type
       Direct exposure 556 (84.4)
       Intrauterine exposure 54 (8.2)
       Entered the city within 2 wk of the bombing 2 (0.3)
       Others 1 (0.2)
       Missing data 46 (7.0)
      Presence of a radiation shield
       None 36 (5.5)
       Partial 101 (15.3)
       Full 352 (53.4)
       Others 2 (0.3)
       Missing data 168 (24.5)
      Reason for visiting Japan
       Residence 500 (75.9)
       Following parents or relatives 77 (11.7)
       Others 50 (7.6)
       Missing data 32 (4.9)
      Symptoms of aftereffects of atomic bomb exposure
       Had aftereffect symptoms 193 (29.3)
       Did not have aftereffect symptoms 134 (20.3)
       Do not know 302 (45.8)
       Missing data 30 (4.6)
      Use of medical care due to aftereffects of atomic bomb exposure
       Used 137 (20.8)
       Did not use 306 (46.4)
       Missing data 216 (32.8)
      Variables Total (n=1,828) Generation
      First (n=659) Second (n=927) Third (n=242)
      Smoking status
       Never smoker 1,179 (64.5) 429 (65.1) 555 (59.9) 195 (80.6)
       Former smoker 408 (22.3) 186 (28.2) 213 (23.0) 9 (3.7)
       Current smoker 240 (13.1) 44 (6.7) 159 (17.2) 37 (15.3)
       Missing 1 (0.1) 0 (0.0) 0 (0.0) 1 (0.4)
      Drinking status
       Lifetime abstainer 823 (45.0) 393 (59.6) 331 (35.7) 99 (40.9)
       Former drinker 196 (10.7) 108 (16.4) 77 (8.3) 11 (4.6)
       Current drinker 805 (44.0) 156 (23.7) 518 (55.9) 131 (54.1)
       Missing 4 (0.2) 2 (0.3) 1 (0.1) 1 (0.4)
      Health status
       Very good 65 (3.6) 16 (2.4) 20 (2.2) 29 (12.0)
       Good 372 (20.4) 82 (12.4) 197 (21.3) 93 (38.4)
       Moderate 625 (34.2) 176 (26.7) 359 (38.7) 90 (37.2)
       Bad 640 (35.0) 312 (47.3) 299 (32.3) 29 (12.0)
       Very bad 125 (6.8) 73 (11.1) 51 (5.5) 1 (0.4)
       Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
      Exercise frequency (times/wk)
       Never 868 (47.5) 353 (53.6) 386 (41.6) 129 (53.3)
       1–2 178 (9.7) 20 (3.0) 123 (13.3) 35 (14.5)
       3–4 322 (17.6) 80 (12.1) 201 (21.7) 41 (16.9)
       4–6 148 (8.1) 47 (7.1) 83 (9.0) 18 (7.4)
       Everyday 311 (17.0) 158 (24.0) 134 (14.5) 19 (7.9)
       Missing 1 (0.1) 0 (0.0) 0 (0.0) 0 (0.0)
      Sleep quality over the past month
       Very good 204 (11.2) 70 (10.6) 84 (9.1) 50 (20.7)
       Good 907 (49.6) 304 (46.1) 477 (51.5) 126 (52.1)
       Bad 565 (30.9) 200 (30.4) 303 (32.7) 62 (25.6)
       Very bad 116 (6.4) 55 (8.4) 57 (6.2) 4 (1.7)
       Missing 36 (2.0) 30 (4.6) 6 (0.7) 0 (0.0)
      Variable Total (n=1,828) Generation
      First (n=659) Second (n=927) Third (n=242)
      X-rays
       Never been exposed 67 (3.7) 32 (4.9) 15 (1.6) 20 (8.3)
       Do not know 559 (30.6) 300 (45.5) 228 (24.6) 31 (12.8)
       Missing 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
       Exposed 1,202 (65.8) 327 (49.6) 684 (73.8) 191 (78.9)
        Mean±SD 17.6±12.9 21.1±13.1 18.0±12.7 10.2±10.0
      Dental panoramic X-rays
       Never been exposed 190 (10.4) 95 (14.4) 69 (7.4) 26 (10.7)
       Do not know 441 (24.1) 263 (39.9) 152 (16.4) 26 (10.7)
       Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
       Exposed 1,196 (65.4) 301 (45.7) 705 (76.1) 190 (78.5)
        Mean±SD 7.9±6.8 10.7±7.9 7.5±6.4 4.9±4.4
      Computed tomography
       Never been exposed 433 (23.7) 71 (10.8) 236 (25.5) 126 (52.1)
       Do not know 396 (21.7) 283 (42.9) 99 (10.7) 14 (5.8)
       Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
       Exposed 998 (54.6) 305 (46.3) 591 (63.8) 102 (42.2)
        Mean±SD 6.1±6.7 11.2±7.9 4.2±4.8 2.2±2.0
      Fluoroscopy
       Never been exposed 1,098 (60.1) 345 (52.4) 551 (59.4) 202 (83.5)
       Do not know 209 (31.7) 65 (7.0) 10 (4.1) 284 (15.5)
       Missing 2 (0.3) 1 (0.2) 0 (0.0) 3 (0.2)
       Exposed 443 (24.2) 103 (15.6) 310 (33.4) 30 (12.4)
        Mean±SD 4.6±6.8 8.3±11.2 3.6±4.4 2.2±2.5
      Nuclear medicine test - oral and intravenous administration of radiopharmaceuticals (bone scan, thyroid scan, PET-CT, SPECT, etc.)
       Never been exposed 1,620 (88.6) 536 (81.3) 851 (91.8) 233 (96.3)
       Do not know 141 (7.7) 99 (15.0) 34 (3.7) 8 (3.3)
       Missing 1 (0.1) 0 (0.0) 1 (0.2) 0 (0.0)
       Exposed 66 (3.6) 24 (3.6) 41 (4.4) 1 (0.4)
        Mean±SD 5.5±10.3 8.3±16.1 3.8±4.0 8.0±.0.0
      Nuclear medicine test - oral and intravenous administration of radiopharmaceuticals (thyroid radioiodine therapy, strontium-89 bone metastasis treatment, etc.)
       Never been exposed 1,677 (91.7) 556 (84.4) 886 (95.6) 235 (97.1)
       Do not know 130 (7.1) 94 (14.3) 31 (3.3) 5 (2.1)
       Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
       Exposed 20 (1.1) 9 (1.4) 9 (1.0) 2 (0.8)
        Mean±SD 6.3±17.5 11.8±25.7 1.6±1.3 2.5±2.1
      Mammography
       Never been exposed 1,002 (54.8) 342 (51.9) 457 (49.3) 203 (83.9)
       Do not know 277 (15.2) 171 (26.0) 101 (10.9) 5 (2.1)
       Missing 3 (0.2) 0 (0.0) 3 (0.3) 0 (0.0)
       Exposed 546 (29.9) 146 (22.2) 366 (39.5) 34 (14.1)
        Mean±SD 8.5±6.4 12.1±7.2 7.6±5.5 3.1±2.6
      Interventional radiography
       Never been exposed 1,668 (91.3) 559 (84.8) 872 (94.1) 237 (97.9)
       Do not know 102 (5.6) 77 (11.7) 20 (2.2) 5 (2.1)
       Missing 1 (0.1) 0 (0.0) 1 (0.1) 0 (0.0)
       Exposed 57 (3.1) 23 (3.5) 34 (3.7) 0 (0.0)
        Mean±SD 3.3±10.5 5.9±16.3 1.5±1.1 0.0±0.0
      Radiation therapy
       Never been exposed 1,686 (92.2) 566 (85.9) 884 (95.4) 236 (97.5)
       Do not know 93 (5.1) 72 (10.9) 16 (1.7) 5 (2.1)
       Missing 3 (0.2) 1 (0.2) 2 (0.2) 0 (0.0)
       Exposed 46 (2.5) 20 (3.0) 25 (2.7) 1 (0.4)
        Mean±SD 17.9±22.2 15.8±20.1 20.3±24.1 1.0±0.0
      Variables Total (n=1,828) Generation χ2 (p-value)
      First (n=659) Second (n=927) Third (n=242)
      Malformations (such as those in the heart and fingers among others) 24 (1.3) 6 (0.9) 12 (1.3) 6 (2.5) 0.186
      Cerebral palsy 3 (0.2) 0 (0.0) 3 (0.3) 0 (0.0) 0.379
      Hypertension 601 (32.9) 367 (55.7) 230 (24.8) 4 (1.7) <0.001
      Hyperlipidemia 589 (32.2) 274 (41.6) 305 (32.9) 10 (4.1) <0.001
      Stroke 78 (4.3) 53 (8.0) 24 (2.6) 1 (0.4) <0.001
      Heart attack/angina 113 (6.2) 83 (12.6) 30 (3.2) 0 (0.0) <0.001
      Osteoarthritis 308 (16.8) 182 (27.6) 124 (13.4) 2 (0.8) <0.001
      Rheumatoid arthritis 74 (4.0) 35 (5.3) 37 (4.0) 2 (0.8) 0.010
      Osteoporosis 287 (15.7) 190 (28.8) 97 (10.5) 0 (0.0) <0.001
      Vertebral stenosis or disc herniation 559 (30.6) 252 (38.2) 285 (30.7) 22 (9.1) <0.001
      Diabetes mellitus 324 (17.7) 195 (29.6) 125 (13.5) 4 (1.7) <0.001
      Benign thyroid disease 212 (11.6) 95 (14.4) 109 (11.8) 8 (3.3) <0.001
      Cancer 198 (10.8) 110 (16.7) 85 (9.2) 3 (1.2) <0.001
      Major depressive disorder 130 (7.1) 55 (8.3) 64 (6.9) 11 (4.5) 0.136
      Parkinson’s disease 8 (0.4) 5 (0.8) 3 (0.3) 0 (0.0) 0.309
      Epilepsy 4 (0.2) 0 (0.0) 4 (0.4) 0 (0.0) 0.195
      Intellectual disability 14 (0.8) 0 (0.0) 10 (1.1) 4 (1.7) 0.003
      Peripheral neuropathy 11 (0.6) 6 (0.9) 5 (0.5) 0 (0.0) 0.366
      Schizophrenia 4 (0.2) 1 (0.2) 3 (0.3) 0 (0.0) 0.799
      Dementia 50 (2.7) 47 (7.1) 3 (0.3) 0 (0.0) <0.001
      Atopy 100 (5.5) 24 (3.6) 42 (4.5) 34 (14.0) <0.001
      Alopecia 85 (4.6) 20 (3.0) 52 (5.6) 13 (5.4) 0.048
      Allergy 178 (9.7) 44 (6.7) 111 (12.0) 23 (9.5) 0.002
      Allergic rhinitis 273 (14.9) 43 (6.5) 151 (16.3) 79 (32.6) <0.001
      Asthma 87 (4.8) 38 (5.8) 40 (4.3) 9 (3.7) 0.293
      Cataract 532 (29.1) 380 (57.7) 151 (16.3) 1 (0.4) <0.001
      Glaucoma 62 (3.4) 39 (5.9) 23 (2.5) 0 (0.0) <0.001
      Macular degeneration 32 (1.8) 18 (2.7) 12 (4.3) 2 (0.8) 0.062
      Hearing loss 113 (6.2) 71 (10.8) 40 (4.3) 3 (1.2) <0.001
      Meniere’s disease 14 (0.8) 2 (0.3) 10 (1.1) 2 (0.8) 0.210
      Male infertility 4 (0.5) 2 (0.6) 2 (0.5) 0 (0.0) 1.000
      Prostate disease 228 (26.6) 166 (53.4) 60 (14.1) 2 (1.7) <0.001
      Vasectomy 96 (11.2) 9 (2.9) 85 (19.9) 2 (1.7) <0.001
      Female infertility 18 (1.9) 1 (0.3) 17 (3.4) 0 (0.0) <0.001
      Uterine myoma 193 (20.6) 44 (13.8) 140 (28.2) 9 (7.4) <0.001
      Tubal ligation 41 (4.4) 16 (5.0) 25 (5.0) 0 (0.0) 0.014
      Pain of unknown origin 175 (9.6) 56 (8.5) 103 (11.1) 16 (6.6) 0.053
      Other diseases 587 (32.1) 196 (29.7) 338 (36.5) 53 (21.9) <0.001
      Variable Total Generation
      First Second Third
      Subtotal 26,712 (100) 10,407 (100) 15,189 (100) 1,116 (100)
       Family member’s generation
        First 4,887 (18.3) 3,505 (33.7) 1,382 (9.1) 0 (0.0)
        Second 7,555 (28.3) 3,335 (32.1) 3,973 (26.2) 247 (22.1)
        Third 5,222 (19.6) 2,873 (27.6) 1,821 (12.0) 528 (47.3)
        Fourth 66 (0.2) 0 (0.0) 0 (0.0) 66 (5.9)
        Not exposed 8,904 (33.3) 645 (6.2) 7,984 (52.6) 275 (24.6)
        Do not know 78 (0.3) 49 (0.5) 29 (0.2) 0 (0.0)
       Sex
        Male 13,255 (49.6) 5,213 (50.1) 7,489 (49.3) 553 (49.6)
        Female 13,187 (49.4) 5,106 (49.1) 7,524 (49.5) 557 (49.9)
        Do not know 270 (1.0) 88 (0.9) 176 (1.2) 6 (0.5)
       Survival status
        Alive 18,921 (70.8) 7,527 (72.3) 10,307 (67.9) 1,087 (97.4)
        Dead 7,524 (28.2) 2,804 (26.9) 4,697 (30.9) 23 (2.1)
        Miscarriage 233 (0.9) 60 (0.6) 167 (1.1) 6 (0.5)
        Stillbirth 8 (0.0) 6 (0.1) 2 (0.0) 0 (0.0)
        Do not know 26 (0.1) 10 (0.1) 16 (0.1) 0 (0.0)
      Father 1,797 (100) 630 (100) 924 (100) 241 (100)
       Exposed history
        Directly exposed 1,075 (59.9) 597 (94.8) 478 (51.7) 0 (0.0)
        Indirectly exposed 88 (4.9) 0 (0.0) 0 (0.0) 88 (36.5)
        Not exposed 609 (33.9) 21 (3.3) 435 (47.1) 153 (63.5)
        Do not know 20 (1.1) 10 (1.6) 10 (1.1) 0 (0.0)
        Missing 3 (0.2) 2 (0.3) 1 (0.1) 0 (0.0)
       Survival status
        Alive 546 (30.4) 3 (0.5) 320 (34.6) 223 (92.5)
        Dead 1,249 (69.6) 627 (99.5) 604 (65.4) 18 (7.5)
      Mother 1,795 (100) 630 (100) 924 (100) 241 (100)
       Exposure history
        Directly exposed 1,223 (68.1) 603 (95.7) 620 (67.1) 0 (0.0)
        Indirectly exposed 160 (8.9) 0 (0.0) 1 (0.1) 159 (66.0)
        Not exposed 396 (22.1) 14 (2.2) 300 (32.5) 82 (34.0)
        Do not know 14 (0.8) 11 (1.8) 3 (0.3) 0 (0.0)
        Missing 2 (0.1) 2 (0.3) 0 (0.0) 0 (0.0)
       Survival status
        Alive 885 (49.3) 4 (0.6) 643 (69.6) 238 (98.8)
        Dead 910 (50.7) 626 (99.4) 281 (30.4) 3 (1.2)
      Brothers and sisters 6,463 (100) 2851 (100) 3326 (100) 286 (100)
       Exposure history
        Directly exposed 1,921 (29.7) 1,643 (57.6) 278 (8.4) 0 (0.0)
        Indirectly exposed 4,438 (68.7) 1,133 (39.7) 3,020 (90.8) 286 (100)
        Not exposed 72 (1.1) 59 (2.1) 13 (0.4) 0 (0.0)
        Do not know 31 (0.5) 16 (0.6) 15 (0.5) 0 (0.0)
       Survival status
        Alive 4,838 (74.9) 1,661 (58.3) 2,893 (87.0) 284 (99.3)
        Dead 1,612 (24.9) 1,181 (41.4) 429 (12.9) 2 (0.7)
        Do not know 13 (0.2) 9 (0.3) 4 (0.1) 0 (0.0)
      Children 4,087 (100) 2,188 (100) 1,833 (100) 66 (100)
       Exposure history
        Directly exposed 1 (0.0) 1 (0.0) 0 (0.0) 0 (0.0)
        Indirectly exposed 4,085 (99.9) 2,186 (99.9) 1,833 (100) 66 (100)
        Not exposed 1 (0.0) 1 (0.0) 0 (0.0) 0 (0.0)
        Survival status
       Alive 3,695 (90.4) 2,003 (91.5) 1,632 (89.0) 60 (90.9)
        Dead 151 (3.7) 119 (5.4) 32 (1.8) 0 (0.0)
        Miscarriage 233 (5.7) 60 (2.7) 167 (9.1) 6 (9.1)
        Stillbirth 8 (0.2) 6 (0.3) 2 (0.1) 0 (0.0)
      Table 1 Questionnaires and measurements used in the Korean Atomic Bomb Survivors Cohort

      Table 2 Baseline socio-demographic characteristics of participants of the Korean Atomic Bomb Survivors Cohort by generation

      Values are presented as number (%).

      Seodang (a traditional village school in Korea) is categorized as “primary school.”

      Table 3 Atomic bomb exposure of first-generation individuals in the Korean Atomic Bomb Survivors Cohort (n=659)

      Table 4 Baseline health behaviors, including smoking and drinking, of participants in the Korean Atomic Bomb Survivors Cohort

      Values are presented as number (%).

      Table 5 Baseline medical radiation exposure history of participants and their offspring by generation of the Korean Atomic Bomb Survivors Cohort

      Values are presented as number (%).

      SD, standard deviation; PET-CT, position emission tomography-computed tomography; SPECT, single-photon emission computed tomography.

      Table 6 Disease prevalence among the participants in the Korean Atomic Bomb Survivors Cohort by generation

      Values are presented as number (%).

      Table 7 Atomic bomb exposure and vital statistics of family members reported by participants in the Korean Atomic Bomb Survivors Cohort, by generation

      Values are presented as number (%).


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