Age-related macular degeneration: Prevalence and risk factors - a cross-sectional study : The Tromsø Study 2007/2008

Abstract

Age-related macular degeneration (AMD) is an important cause of visual impairment and blindness worldwide. The number of people affected by the disease is expected to rise due to increasing longevity. Development of adequate eye care for these patients should be based on knowledge about the prevalence of AMD. Further, preventive measures are the best strategy for any disease. The aims of this thesis were to estimate the prevalence of AMD and examine risk factors associated with AMD. We described prevalence rates of AMD among Caucasian elderly participants from the Tromsø Eye Study, a population-based study in Norway. The overall prevalence of late AMD was 3.5 % among the participants aged 65-87 years old. Neovascular AMD outnumbered geographic atrophy. Symmetry between eyes was relatively low. Prevalence increased strongly with age. No significant sex differences in prevalence rates of AMD were observed. Refractive error was lower in eyes with late AMD than in eyes without late AMD. We then analysed relationships between traditional cardiovascular risk factors and AMD. Daily smoking was a strong predictor for the presence of late AMD. We found a significant interaction between age and sex for late AMD, suggesting that age may be a stronger risk factor for late AMD in women than in men. Higher systolic blood pressure, higher pulse pressure, infrequent physical exercise and overweight or obesity were in adjusted analyses associated with late AMD in females, but this was not observed in men. Based on our observation of sex and AMD, we studied associations between female hormone related factors and AMD. We found a significant inverse relationship between duration of lactation and late AMD. No significant relationships were found between late AMD and exogenous oestrogen exposure in the form of contraceptives or hormone therapy. Nor did we find an association between late AMD and onset, end or length of fertile years, bilateral oophorectomy or parity as surrogate measures.