Glucose control and cognitive and physical function in adults 80+ years of age with diabetes

INTRODUCTION: We modeled associations between glycated hemoglobin (HbA1c) levels (<7%, 7% to 8%, and >8%) and cognitive and physical function among adults 80+ years of age with diabetes and determined whether associations differ by frailty, multimorbidity, and disability. METHODS: A total of 316, adults with diabetes, 80+ years of age, were from the Adult Changes in Thought Study. The Cognitive Abilities Screening Instrument Item Response Theory (CASI‐IRT) measured cognition. Short performance‐based physical function (sPPF) and gait speed measured physical function. Glycosylated hemoglobin (HbA1c) levels were from clinical measurements. Analyses estimated associations between average HbA1c levels (<7%, 7% to 8%, and >8%) and functional outcomes using linear regressions estimated with generalized estimating equations. RESULTS: sPPF scores did not differ significantly by HbA1c levels. Gait speed did, but only for non‐frail individuals; those with HbA1c >8% were slower (‐0.10 m/s [95% CI, −0.16 to −0.04]) compared to those with HbA1c 7% to 8%. The association between HbA1c and CASI‐IRT varied with age (interaction P = 0.04). At age 80, for example, relative to people with HbA1c levels of 7% to 8%, CASI‐IRT scores were, on average, 0.18 points lower (95% CI, −0.35 to −0.02) for people with HbA1c <7% and 0.22 points lower (95% CI, −0.40 to −0.05) for people with HbA1c >8%. At older ages, these estimated differences were attenuated. Estimated associations were not modified by multimorbidity or disability. DISCUSSION: Moderate HbA1c levels of 7% to 8% were associated with better cognition in early but not late octogenarians with diabetes. Furthermore, HbA1c >8% was associated with slower gait speed among those without frailty. These results add to an evidence base for determining glucose targets for very old adults with diabetes.