People who lack essential antioxidants, and who have high levels of sunlight exposure, have a higher risk of developing advanced macular degeneration (AMD), according to a study published today in the journal Archives of Ophthalmology. AMD is the leading cause of poor vision in the UK.
The EUREYE study, led by Astrid Fletcher, Professor of Epidemiology of Ageing at the London School of Hygiene & Tropical Medicine, is the first to report in human populations an adverse association between sunlight exposure and AMD in people with low levels of antioxidants. It is also unprecedented in the level of detail the researchers used, taking into account not only lifestyle and medical factors but even going so far as to estimate levels of cloud cover in each of the countries from which participants were recruited.
The eye is particularly vulnerable to the damaging effects of sunlight. Ultraviolet radiation is absorbed by the lens, but visible or "blue" light penetrates to the retina so allowing us to see. Protection against the harmful effects of blue light is provided by the antioxidant vitamins C and E, the carotenoids (lutein and zeaxanthin) which filter blue light, and zinc.
Animal and laboratory studies have previously shown that blue light may be a factor in the pathogenesis of AMD, but results have been inconsistent in the few studies that have investigated associations between sunlight exposure and AMD in human populations. Little attention has been paid to the possible interactions between antioxidant levels and light exposure, although it is thought that the adverse effects of sunlight may be mitigated by the protective effects of antioxidants.
4,753 participants aged 65 years were selected randomly in seven centres, Bergen in Norway, Tallinn in Estonia, Belfast in the UK, Paris-Creteil in France, Verona in Italy, Thessaloniki in Greece and Alicante in Spain. The average age of participants was 73.2 and 55% were women. Blue light exposures tended to be higher in participants from centres in southern Europe while participants in an exclusively urban centre (Paris) had the lowest exposures.
Participants underwent fundus photography, and gave a blood sample for antioxidant analysis. They completed a residence and job history in advance, and attended a face-to-face interview. They were asked about their education, smoking and alcohol use, medical history, lifetime residence and level of sunlight exposure, including how much time they had spent outdoors between the hours of 9am and 5pm, and 11am and 3pm each day since they left school and throughout their working life.
Information was collected separately for summer and winter, and for different occupational time periods (including time spent looking after the home) and in retirement up to their current age. For each period, they were asked about their use of eyewear (glasses, contact lenses and sunglasses). The information on sunlight exposure and area of residence was sent to the University of East Anglia and combined with metrological information to estimate lifetime blue light exposure for each participant.