Relation of age-related macular degeneration and cognitive impairment in an older population

Abstract

Background: The aetiology of age-related macular degeneration (AMD) and cognitive impairment is poorly understood. A link between cognitive impairment and AMD has been proposed although only a weak association was found in population-based studies.

Purpose: To assess cross-sectional associations between AMD and cognitive impairment in an older Australian population.

Methods: The Blue Mountains Eye Study examined 3,509 persons aged 49+ years during 1997-2000. AMD lesions were assessed from retinal photographs using the Wisconsin System. Mini-mental state examination (MMSE), demographics, lifestyle factors and medical history were collected at interview. MMSE score was categorised as high-normal (28-30), low-normal (24-27) and impaired (< 24). A modified MMSE excluded five vision related items and was dichotomised as normal (18-22) and impaired (0-17). Logistic regression was used to assess associations after adjusting for age, sex, visual impairment, stroke, current smoking status, hypertension, alcohol consumption and post-high-school qualification.

Results: Prevalence rates for late and early AMD were 1.5% (n = 50) and 8.3% (n = 273), respectively. Cognitive impairment was present in 18.0% in persons with late AMD and 8.4% with early AMD, compared to 2.6% in persons without AMD. After multivariate adjustment, late AMD was associated with low normal MMSE (odds ratio (OR): 2.2, 95% confidence interval (CI): 1.1-5.0) and cognitive impairment (OR: 3.7, CI: 1.3-10.6). Using the modified MMSE, the multivariate association between late AMD and cognitive impairment remained (OR: 2.2, CI: 1.0-5.0). No significant association was found between cognitive impairment and early AMD.

Conclusions: We found a significant, cross-sectional association between late AMD and cognitive impairment in a sample of older Australians that appeared to be independent of visual impairment. The association was weaker but remained significant after excluding vision-related items from the MMSE.