A team of medical doctors from the Erasmus University Medical School has released the results of a major study into a possible connection between age-related macular degeneration and Alzheimer's disease. Macular degeneration (age-related maculopathy) and Alzheimer's disease are both chronic neurodegenerative disorders, which are characterized by extracellular plaque deposits either in the macula of the retina or in the brain. Both disorders are more prevalent among smokers and people with atherosclerosis. Their study involved 1438 Dutch men and women aged 75 years or older. The participants underwent a thorough medical and ophthalmologic examination and were screened for signs of dementia at the beginning of the study and after two years of follow-up.

At baseline, 43.6 per cent of the participants were diagnosed with age-related maculopathy of varying severity; none had signs of Alzheimer's disease at this stage. Two years later, 62 of the participants had developed Alzheimer's disease. This corresponds to an incidence rate of 14 per 1000 person-years in the 75 to 84 year age group and 41.6 per 1000 person-years in those aged 85 years or older. The researchers discovered a clear relationship between the presence of moderate to severe (stage 3 and 4) maculopathy at baseline and the incidence of Alzheimer's disease two years later. The incidence of Alzheimer's was found to be twice as high among participants with moderate to severe maculopathy as among participants with no or less severe maculopathy. The risk factor was reduced to 1.5 (a 50 per cent excess risk) when the data was adjusted for age, gender, smoking, and atherosclerosis. The researchers conclude that macular degeneration and Alzheimer's disease may have a common origin and that both diseases may be causally linked to smoking and atherosclerosis.
Klaver, Caroline C.W., et al. Is age-related maculopathy associated with Alzheimer's disease? American Journal of Epidemiology, Vol. 150, November 1, 1999, pp. 963- 68