Influence of Diabetes Duration and Glycemic Control on Dementia: A Cohort Study

Background: To investigate the influence of diabetes duration and glycemic control, assessed by glycated hemoglobin (HbA1c) levels, on risk of incident dementia. Methods: The present study is a prospective study of 461 563 participants from the UK Biobank. The age at diabetes diagnosis was determined by self-report. Diabetes duration was calculated as baseline age minus age at diagnosis. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) with 95% confidential intervals (CIs). Results: During a median follow-up of 8.1 years, 2 233 dementia cases were recorded. As compared with normoglycemic individuals, individuals with diabetes had higher risk of all-cause dementia, and the risk increased with increasing duration of diabetes; compared with participants with diabetes duration of <5 years, the multivariable-adjusted HRs (95% CIs) were 1.49 (1.12-1.97), 1.71 (1.21-2.41), and 2.15 (1.60-2.90) for those with diabetes durations >= 5 to < 10, >= 10 to <15, and >= 15 years, respectively (p for trend < .001). Among participants with diabetes, those with both longer diabetes duration (diabetes duration >= 10 years) and poor glycemic control (HbA1c >= 8%) had the highest risk of all-cause dementia (multivariable-adjusted HR = 2.07, 95% CI 1.45, 2.94), compared with patients with shorter duration of diabetes and better glycemic control (diabetes duration < 10 years and HbA1c < 8%). Conclusions: Diabetes duration appeared to be associated with the risk of incident dementia due to factors beyond glycemic control. Clinicians should consider not only glycemic control but also diabetes duration in dementia risk assessments for patients with diabetes.