NEW YORK (Reuters Health) – Elderly individuals with cognitive impairment may be more likely than those with intact cognitive function to have early age-related macular degeneration (AMD), according to findings from the Cardiovascular Health Study published in the May Archives of Ophthalmology.

“Alzheimer disease and AMD have long been hypothesized to share a common pathogenesis based on several lines of evidence,” Dr. Tien Yin Wong of the University of Melbourne, Australia, and co-authors write, including similar histopathologic changes, common vascular risk factors, and possibly shared genetic loci. Clinical and epidemiological studies of this association are lacking, however.

The researchers’ “large, ethnically diverse, population-based” study cohort included 2008 subjects, ages 69 to 97 years, from four counties in the US who underwent retinal photography and assessment of cognitive function and dementia in 1997 or 1998.

Median scores on the Digit Symbol Substitution Test (DSST) were lower among the 324 subjects with AMD than those without AMD (39 vs 41, p < 0.001), Dr. Wong and colleagues report. After controlling for sociodemographics, risk factors, and apolipoprotein E genotype, subjects in the lowest quartile of DSST scores were twice as likely to have early AMD. However, a diagnosis of dementia or Alzheimer disease according to detailed neuropsychological testing was not significantly associated with early AMD. Still, in analyses excluding those with dementia (n = 135), the association between DSST score and early AMD remained statistically significant (adjusted OR 2.0). “These data, along with others, provide further support that AMD and cognitive impairment may share similar complex pathogenesis and risk factors,” the researchers conclude. Reference:
Arch Ophthalmol 2009;127:667-673.