Vascular risk factors and cognitive decline among elderly male twins

Background: Studies investigating the association between cardiovascular risk factors and cognitive decline report discrepant outcomes. The co-twin control method improves on traditional case-control approaches by controlling for within-twin pair similarities of genetic and early environmental influences. Objective: To examine the association of diabetes, hypertension, hypercholesterolemia, and elevated body mass index (BMI) (> 30 kg/m(2)), individually and combined, with cognitive decline over a 12-year period in members of the National Academy of Sciences-National Research Council Twin Registry of World War II male veterans. Methods: Modified Telephone Interview for Cognitive Status (TICS-m) was administered four times at approximately 4-year intervals from 1990 to 2002 as part of an epidemiologic study of dementia. Self-report medical information was collected from 1996 to 2002. We examined the difference in cognitive decline within twin pairs discordant for the vascular risk factors while controlling for baseline TICS-m, education, smoking, and alcohol history. Results: Among twin pairs discordant for diabetes (n = 177), the diabetic twins declined an average of almost 1 point more than their nondiabetic co-twins (p = 0.018) at the last screening time point. Further analyses showed that this was in large part due to greater decline among older men ( age 76 to 84 years). Cognitive change was not significantly different between members of pairs discordant for hypertension (n = 326), hypercholesterolemia (n = 282), or elevated BMI (n = 166). Conclusion: Based on this study of twin pairs who share similar genetic and early environmental risks for cardiovascular risk factors, diabetes is associated with greater cognitive decline, particularly among the oldest individuals.