Diabetes mellitus as a modulator of functional impairment and decline in Alzheimer’s disease. The Real.FR cohort

AIMS: To determine whether diabetes mellitus influences functional status in patients with Alzheimer's disease. METHODS: We studied 608 community-dwelling patients with Alzheimer's disease from a prospective multicenter cohort. Diabetes was assessed at baseline. Functional status was assessed twice yearly with the Activities of Daily Living scale. Each patient had a baseline functional disability if their Activities of Daily Living score was < 6. Progression of functional disability was defined by a decreased Activities of Daily Living score over 4 years of follow-up visits. RESULTS: At baseline, diabetes was present in 63 participants (10.4%) and, compared with those without diabetes, was associated with functional impairment [age- and sex-adjusted OR = 2.73 (95% CI 1.41-5.28)]. After controlling for confounders, the association remained significant [OR = 2.04 (95% CI 1.02-4.11)]. Follow-up demonstrated a significant interaction between duration of Alzheimer's disease and diabetes, which was associated with progression of functional impairment in patients who had been diagnosed with Alzheimer's disease for less than 1 year [age- and sex-adjusted hazard ratio = 1.52 (95% CI 1.01-2.30), P = 0.048], but not in those who had been diagnosed with Alzheimer's disease for more than 1 year [age- and sex-adjusted hazard ratio = 0.78 (95% CI 0.47-1.28), P = 0.32]. Abnormal one-leg balance, polymedication and obesity seem to be important factors explaining the association between diabetes and functional status. CONCLUSIONS: At baseline, the presence of diabetes significantly increases the risk of functional disability in patients with Alzheimer's disease; our longitudinal data confirm that in patients with a recent diagnosis of Alzheimer's disease (but not in those who have had Alzheimer's disease for longer than 1 year), diabetes continues to worsen functional status.