UVR Exposure and Risk of Neovascular Age-Related Macular Degeneration

Abstract

Purpose:: Findings have not been in agreement as to a causative or protective effect of sunlight exposure on risk of age-related macular degeneration (AMD). Therefore we evaluated UVR (Ultraviolet Radiation) Index, UV-A, and UV-B as a measure of sunlight exposure on risk of neovascular AMD.

Methods:: We obtained epidemiological data by conducting telephone or in-person standardized interviews with 135 extremely discordant sibpairs (index case with neovascular AMD [mean age = 71.4 yrs] and sibling with normal maculae past the age of diagnosis of the index patient [mean age = 72.8 yrs]) from 135 families. Disease status was ascertained by two investigators by review of fundus photographs. If necessary, a home retinal examination was performed (n =6). Exposure data were measured up to the age of AMD diagnosis of the index subject. We determined UVR index, UV-A, and UV-B measures by inputting the city and state at which the individual resided for the majority of his or her lifetime using the following website: http://cprm.acd.ucar.edu/Models/TUV/Interactive_TUV/. This calculator uses longitude, latitude and elevation to estimate UVR levels. We assessed the relationship between neovascular AMD and UVR levels using McNemar’s test.

Results:: A decrease in risk of neovascular AMD was observed in subjects with lifetime UV index exposure greater than or equal to 3.0 when compared to those with a UV index of less than 3.0 (OR: 0.23, 95% CI: 0.08-0.52, p =.0002), (number of informative sibpairs: n = 38). Similar results were obtained when we caluclated UV-A or UV-B exposures separately. Individuals with a lifetime UV-B exposure of 0.60 or greater compared to individuals who had measures less than 0.60, had a 14-fold reduction in risk of neovascular AMD (p < 0.001.), (number of informative sibpairs: n = 30). Subjects with a lifetime UV-A exposure of 31.6 or greater compared to those with a measure of less than 31.6 had a 2.7 fold decrease in risk ( p = 0.009), (number of informative sibpairs: n = 37) .

Conclusions:: In this cohort of extremely discordant sibpairs, preliminary analysis revealed that subjects who were exposed to higher UVR levels (UVR Index, UV-A, or UV-B) for the majority of their lifetimes were less likely to develop neovascular AMD than subjects who were exposed to lower UVR levels.

Keywords: age-related macular degeneration • clinical (human) or epidemiologic studies: risk factor assessment • radiation damage: light/UV