AMD Risk Higher Among Outdoor Workers

Norra MacReady

April 15, 2016

Some cloudy news for people who work outdoors: long hours in the sun may increase the risk for age-related macular degeneration (AMD).

Compared with little or no time spent working in the sun, past but not current sun exposure showed a dose-related increase in the risk for early and late AMD among retirees, researchers report in an article published in the April issue of Retina.

"[S]unlight exposure at younger age has an influence on the development of a severe eye disease...decades later," write Tina Schick, MD, from the Department of Ophthalmology, University Hospital of Cologne, Germany, and colleagues. "The results also demonstrate that the predisposing events for the disease take place many years before morphological signs become apparent."

The researchers studied 3701 people participating in the European Genetic Database (EUGENDA). In addition to standard demographic data and smoking history, the authors collected information on occupation type, iris color, and current and past (preretirement) sun exposure: either less than 8 hours daily or 8 or more hours daily. People who rarely went outside served as the reference group.

The authors used fundus photographs to stage the AMD. They defined early AMD as the presence of 10 or more small drusen and pigmentary changes, or intermediate or large drusen on the Early Treatment Diabetic Retinopathy Study grid; they defined late AMD as AMD with subfoveal geographic atrophy and/or choroidal neovascularization in at least one eye.

The group had a mean age of 72.20 ± 8.71 years and included 2186 women (59.1%). Early AMD was seen in 752 individuals (20.3%), and late AMD in 1179 (31.9%). The remaining 1770 (47.8%) participants had no AMD.

Past sun exposure showed a significant association with early AMD (<8 hours outdoors: odds ratio [OR], 5.05 [95% confidence interval (CI), 1.19 - 21.47; P = .03]; ≥8 or more hours outdoors: OR, 6.32 [95% CI, 1.45 - 27.50; P = .01]). Higher past sun exposure was also associated with late AMD (<8 hours: OR, 0.92 [95% CI, 0.48 - 1.78; P = .81]; ≥8 or more hours: OR, 2.65 [95% CI, 1.34 - 5.24; P = .005]).

After adjustment for age, sex, and smoking history, greater past sun exposure remained significantly associated with early (<8 hours: OR, 4.94 [95% CI, 1.14 - 21.34; P = .03]; ≥8 or more hours: OR, 5.54 [95% CI, 1.25 - 24.58; P = .02]) and late (<8 hours: OR, 1.14 [95% CI, 0.53 - 2.45; P = .74]; ≥8 or more hours: OR, 2.77 [95% CI, 1.25 - 6.16; P = .01]) AMD.

When they analyzed the data according to work location, rather than sun exposure, the authors found a highly significant association between outside work (compared with inside work) and late AMD (OR, 2.70; 95% CI, 2.09 - 3.49; P = 1.31 × 10−13). This association persisted after adjustment for age, sex, and smoking history (OR, 2.57; 95% CI, 1.89 - 3.48; P = 1.58 × 10−9).

On adjusted analysis, the risk for AMD was not significantly associated with current sun exposure, iris color, or specific occupation type, other than the amount of time spent in the sun.

These findings suggest that "past sunlight exposure and outside working [are] important environmental risk factors for AMD," the authors conclude. Considering that sunlight exposure is also a risk factor for conditions such as cataracts and skin cancer, they warn that "preventive measures, for example wearing sunglasses and brimmed hats to minimize sunlight exposure, should start early to prevent development of AMD and other diseases later in life."

The authors have disclosed no relevant financial relationships.

Retina. 2016;36:787-790. Abstract

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