A dose-response effect between a sunlight index and age-related cataracts. Italian-American Cataract Study Group.

To explore the existence of a dose-response relationship between sunlight exposure and risk of age-related cataracts, we analyzed data collected from 1008 patients with cataracts and 469 control subjects enrolled in the Italian-American Case-Control Study of Age-Related Cataracts. Fourteen variables related to sunlight exposure history were included in the questionnaire administered to the study participants. A sunlight index was constructed and its relationship to the presence of cataracts was modeled by logistic regression. After adjustments for potential confounding variables and for age and sex, a significant dose-response effect (P = 0.01) was detected between the sunlight exposure index and the presence of pure cortical cataracts. With the exception of corticonuclear cataracts, all the other mixed types of opacity also showed a dose-response association with the sunlight index. These data support the hypothesis that sunlight exposure is a risk factor in the development of cortical cataracts, and demonstrate the existence of a dose-response relationship in this association.