Sun worshippers still have to worry about potential damage to their skin from catching too many rays, but excessive sun exposure and other related factors do not appear to contribute to the development of age-related macular degeneration.

A new study in Januarys British Journal of Ophthalmology supports this latter conclusion.1

In this study, we have been unable to demonstrate an association between AMD and sun exposure, iris color or change in iris color, the researchers conclude. For the GA [geographic atrophy] form of end-stage AMD, an association with sunburn-prone skin reached borderline significance, but this could be attributable to multiple testing.

Too much sun may cause skin damage but probably not macular degeneration.

Previous theories supported the concept that sun exposure, skin sensitivity to the sun and iris color were linked to AMD, although none of these theories has been backed by published reports.

In this study, researchers at the University of Cambridge, in the United Kingdom, compared 446 patients who had end-stage AMD to 283 spouse controls. Data on sun exposure, places of residence, iris color, subjective assessment of change in iris color, hair color at age 20 and skin sensitivity were all considered. All variables were included in a multiple logistic regression model that also included age, sex and smoking.

 Smoking is a well established risk factor for AMD and therefore a potential confounder in studies such as this, the researchers say. From a detailed analysis of smoking parameters, which we report elsewhere, we have shown that pack years of smoking cigarettes is the measure most strongly associated with risk of AMD, and we incorporated this in our logistic regression model.

The researchers were unable to demonstrate a link between estimated lifetime sun exposure and late AMD, which is consistent with the findings of other studies. Data from the Beaver Dam Eye Study, for example, demonstrated an association between sun exposure and early age-related maculopathy in men but no association between sunlight and AMD.2

1. Khan JC, Shahid H, Thurlby DA, et al. Genetic Factors in AMD Study. Age related macular degeneration and sun exposure, iris colour, and skin sensitivity to sunlight. Br J Ophthalmol 2006 Jan;90(1):29-32.
2. Tomany SC, Cruickshanks KJ, Klein R, et al. Sunlight and the 10-year incidence of age-related maculopathy: the Beaver Dam Eye Study. Arch Ophthalmol 2004 May;122(5):750-7.

Vol. No: 143:02Issue: 2/15/2006