Age-Related Macular Degeneration prevalence in Portugal: the Coimbra Eye Study - Report 2

Abstract

Purpose: The Coimbra Eye Study is the first population-based study on Age-Related Macular Degeneration (AMD) including Portuguese subjects. Besides being located in Southern Europe, Portugal presents distinct environmental characteristics that might influence AMD. After our first report about the prevalence of the disease in a coastal town, the aim of this second report was to include an inland town population in our prevalence estimates and two compare both.

Methods: Cross-sectional study, including two Portuguese populations aged ≥ 55 years: one from a coastal town and the second from an inland town. All participants were inquired about their past medical history and submitted to complete ophthalmological exam. Color fundus photographs were also obtained for AMD grading, which was performed using a semi-automated software by a certified reading center, according to the Rotterdam staging. Patients with poor dilation or poor quality images were excluded.

Results: Of the 6023 subjects enrolled, 99.55% were included in the analysis (2975 from the coastal town and 3021 from the inland village). This population was not representative of the age categories ≥ 75 years, so all analyses were weighted by age and gender. Eighty percent of the included subjects presented no signs of age-related maculopathy (ARM) (79.80%; 95%CI:78.77% - 80.83%), while 1.16% (95%CI:0.85%-1.43%) presented late AMD. ARM was significantly more prevalent in women (21.39%, 95% CI:19.96%-22.82%) than in men (18.67%, 95% CI:17.18%-20.16%; p=0.010), but no gender differences were found regarding AMD. Multivariate logistic regression revealed that older age (OR:1.04, p<0.001), other ophthalmological diseases (OR:2.17, p<0.001) and hypertension (OR = 1.16, p=0.037) were significant predictors of AMD. In the inland town, ARM (21.68%; 95% CI:20.21%-23.13%) and AMD (16.68%, 95% CI:15.35%-18.1%) were significantly more prevalent than in the coastal town (7.66%, 95% CI:6.70%-8.62% and 18.39%, 95% CI:16.99%-19.78% respectively, p≤ 0.001). The first presented a significantly higher proportion of smokers and ex-smokers (p<0.001).

Conclusions: The prevalence of late AMD in this Portuguese population was 1.16%, which is lower than most of what has been previously reported for other countries. In the included inland population the prevalence was significantly higher. Further analysis will be needed to completely unravel the underlying risks for this difference.