RERF Report No. 13-14

Paper published in Investigative Ophthalmology and Visual Science§“Exposure to Atomic Bomb Radiation and Age-related Macular Degeneration inLater Life: The Hiroshima-Nagasaki Atomic Bomb Survivor Study”
Katsumasa Itakura, Ikuno Takahashi, Eiji Nakashima, Masahide Yanagi, Ryo Kawasaki, Kazuo
Neriishi, Jie Jin Wang, Tien Yin Wong, Ayumi Hida, Waka Ohishi, Yoshiaki Kiuchi
Invest Ophth Vis Sci 2015 (August); 56(9):5401-6(doi: 10.1167/iovs.15-16680)
Study Findings
Analyses adjusted for age, sex, city, smoking status, and other relevant factors in atomic
bomb survivors indicated no significant association between the prevalence of age-related
macular degeneration and prior radiation exposure.
Explanation
In age-related macular degeneration (AMD), the macula at the center of the retina (thelight-sensitive lining of the eye) degenerates with age, which leads to visual impairment. AMD
is the leading cause of vision loss among adults in many Western countries and constitutes animportant societal issue as a major cause of vision loss in Japan, where an aging population andWesternized lifestyles have increased incidence of the disease. Age-related degeneration of theretina and choroid (the layer underlying the retina), genetic polymorphism, environmental
factors, chronic inflammation, and ischemia each play important roles in AMD development. As
they age, atomic bomb survivors may be at increased risk of AMD, but the relationship between
AMD and radiation exposure has remained unclear.
1. Objective
The objective was to investigate the association between radiation exposure from the atomic
bombings and the prevalence of AMD among atomic bomb survivors in Hiroshima andNagasaki who have been followed by the Radiation Effects Research Foundation throughbiennial health examinations (Adult Health Study: AHS) since 1958.
2. Methods
The 2,153 participants in AHS ophthalmological examinations from 2006 to 2008
underwent a fundoscopic examination with a non-mydriatic fundus camera (TopconTRC-NW200, made in Japan). The resulting fundus images were used to grade the progressionof lesions and classify the disease as early or late AMD. When lesion severity differed between
the eyes, the eye with greater severity was considered. Eye doses determined with the DS021

RERF Report No. 13-14

dosimetry system were used in the analyses. Logistic regression models*1 were used to assess
the association of radiation exposure and AMD prevalence, with adjustments made for relevant
factors (e.g., age, sex, city, smoking status, body mass index, diabetes mellitus, hypertension,
hyperlipidemia, white blood cell count).
*1 Logistic regression models: When a disease (A) is associated with multiple factors (B, C, D,
E…) and the effect of B on A is to be determined, the effects on A of the factors other than B(i.e., C, D, E…) must be adjusted for. Logistic regression models are widely used inepidemiological research to adjust for such factors.
3. Results
Fundus images were gradable for AMD for 1,824 of the participants (84.7%). (The meaneye dose was 0.45 gray (Gy)). The prevalence of early AMD was 10.5%, and that of late AMD
0.3%. Analyses adjusted for age, city, and smoking status indicated no significant association
between AMD prevalence and radiation exposure, resulting in adjusted odds ratio (95%confidence interval) per 1 Gy of 0.93 (0.75 to 1.15) for early AMD and 0.79 (0.21 to 2.94) forlate AMD. The prevalence of small drusen*2 (diameter < 125 μm), which is a precursor to AMD,decreased with dose, but the difference was statistically insignificant.
*2 Drusen: Deposits of metabolic waste products under the retina.

4. Discussion
No association was observed between AMD prevalence and radiation exposure early in life.
A lack of statistical power, however, cannot be ignored, because this was the first study toevaluate AMD prevalence using fundus images and very few participants had late AMD.
Further follow up on AMD development and progression will be needed.

The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring inHiroshima and Nagasaki for more than 60 years. RERF’s research achievements are considered theprincipal scientific basis for radiation risk assessment by the United Nations Scientific Committee on theEffects of Atomic Radiation (UNSCEAR) and for recommendations regarding radiation protection
standards by the International Commission on Radiological Protection (ICRP). RERF expresses its
profound gratitude to the A-bomb survivors and survivors’ offspring for their cooperation in our studies.
§Investigative Ophthalmology & Visual Science (IOVS), published as ready online, is apeer-reviewed academic journal of the Association for Research in Vision and Ophthalmology(ARVO). IOVS features original research, mostly pertaining to clinical and laboratory ophthalmology
and vision research in general. IOVS is regarded as a premier basic science journal for the field ofophthalmology. (Impact factor in 2013: 3.661)

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