Age-related macular degeneration and risk for stroke

Age-related macular degeneration (AMD) affects 7 million persons 40 years of age and older in the United States. Risk factors for the disease are similar to those for stroke.

To determine what relationship, if any, exists between AMD and incident clinical stroke.

Prospective cohort study.

The population-based Atherosclerosis Risk in Communities Study, which was conducted in Minnesota, Maryland, Mississippi, and North Carolina.

10 405 persons between 49 and 73 years of age who had no history of stroke or coronary heart disease.

Participants had retinal photographs taken between 1993 and 1995. A standardized protocol was used to evaluate the photographs for the presence of drusen and other signs of AMD. Incident stroke events were identified and validated by reviewing case records.

There were 498 early-stage and 10 late-stage cases of AMD in the cohort (n = 508). Over a 10-year period, 241 persons had an incident stroke event. After adjusting for age, sex, ethnicity, and site, the authors found that persons with early-stage AMD had a higher cumulative incidence of stroke than those without the disease (4.08% vs. 2.14%). The presence of early-stage AMD was associated with a higher adjusted risk for stroke (hazard ratio, 1.87 [95% CI, 1.21 to 2.88]). Further adjustment for systolic blood pressure, diabetes, cigarette smoking, and use of antihypertensive medications did not substantially alter this association (hazard ratio, 1.85 [CI, 1.19 to 2.87]). The authors found that the association between early-stage AMD and stroke varied by study site and patient ethnicity. Multivariable-adjusted hazard ratios were 3.15 and 1.07 in samples of white patients in Minnesota and Maryland, respectively; 3.77 in a sample of African-American patients in Mississippi; and 0.33 in a sample of mostly white patients (91%) in North Carolina. No site included sufficient numbers of both African-American and white patients to determine whether ethnicity contributed to the observed differences by study site.

There were few cases of late-stage AMD, and the cohort assembly method prohibited full understanding of variation by ethnicity and site.

Middle-aged persons with signs of early-stage AMD have a higher risk for stroke independent of traditional stroke risk factors.