Correlation between UVB irradiation and the proportion of cataract--an epidemiological study based on a nationwide patient survey in Japan.

Among the multiple factors affecting the human eye in work environment, ultraviolet B irradiation (UVB) has received much attention recently. To provide a clear information for the association between cataract and UVB irradiation, the prevalence data from the Patient Survey and UVB estimates in all the 47 prefectures in Japan were used to examine the relationship between cataract and UVB. In analyzing the relationship, we controlled possible effect modifiers; which were aged, that is 65 years old (yo.) or older, population per ophthalmologist, proportions of all the patients among the aged population and proportion of very elderly population (75 yo. or older) among the aged population. A sex-specific logistic regression analysis revealed that the adjusted odds ratio in women was 1.118 with a 95% confidence interval of 1.058-1.183. However, the adjusted odds ratio in men was not statistically significant (1.048 with 95% confidence interval 0.968-1.135). The unstable results of this study may be largely due to the non-definitive estimation of UVB exposure that this kind of study should be repeated when more valid UVB estimates is available.