Type 2 diabetes mellitus and cognitive decline in two large cohorts of community-dwelling older adults

OBJECTIVES: To relate diabetes mellitus (DM) status and duration to late-life cognitive impairment and decline in men and women. DESIGN: Prospective cohort. SETTING: Community. PARTICIPANTS: Five thousand nine hundred seven men in the Physicians' Health Study II and 6,326 women in the Women's Health Study (mean age 74.1 and 71.9, respectively, at baseline cognitive assessment); 553 men and 405 women had DM. MEASUREMENTS: Primary outcomes were general cognition (the Telephone Interview for Cognitive Status (TICS) and a global score averaging five tests) and verbal memory. All participants had second assessments approximately 2 years later; women had third assessments an average of 4 years later. RESULTS: In adjusted linear regression models, participants with DM had significantly lower baseline scores for all outcomes, and longer duration of DM was associated with lower scores (P-trends <.001). Men with DM had significantly greater 2-year cognitive decline than men without DM, and longer duration of DM was associated with worse decline (P-trends <=.01). In repeated-measures analyses of response profiles, women with DM had significantly greater 4-year cognitive decline in all outcomes than women without DM. In women, as in men, there was generally greater cognitive decline with longer duration of DM (e.g., the adjusted mean difference in decline on the TICS associated with duration of >= 5 years was -0.74 (95% confidence interval=-1.05 to -0.43) points (P-trend <.001). There were no significant sex-DM interactions. CONCLUSION: Type 2 DM and longer duration of DM are similarly related to cognitive impairment and decline in men and women.