Longitudinal changes in cognitive function and its related factors in older type 1 diabetes mellitus patients without dementia

Aims This study aimed to assess the longitudinal changes in cognitive function and associated factors in older patients with type 1 diabetes mellitus without dementia. Materials and Methods Older patients above 65 years of age with type 1 diabetes mellitus and without dementia were included in this study. They were assessed using the Mini‐Mental State Examination and Montreal Cognitive Assessment, Japanese version, at baseline and 3 years after. Cognitive decline was defined as a reduction of two or more points in the total Montreal Cognitive Assessment score over 3 years. Baseline diabetes‐related factors were compared between the cognitive decrement and non‐decrement groups to identify risk factors associated with cognitive impairment. Results Twenty‐eight patients aged 71.5 ± 4.0 years were included. Total scores for the Mini‐Mental State Examination and the Montreal Cognitive Assessment (Japanese version) at baseline and after 3 years of follow‐up showed no significant changes ( P = 0.38, P = 0.26). Delayed recall sub‐scores of both tests were significantly lower after 3 years compared to their corresponding levels at baseline ( P = 0.007, P = 0.04); 32% experienced impaired cognition after 3 years compared to baseline examination. Decline in total Montreal Cognitive Assessment score was significantly associated with the onset age ( β = 0.54, P = 0.026) and duration of type‐1 diabetes mellitus ( β = −4.77, P = 0.026). Conclusions Patients with type‐1 diabetes mellitus without dementia experience a progressive decline in memory over time. Long durations of type‐1 diabetes mellitus are associated with cognitive decline even without dementia.