The Long-Term Effects of Type 2 Diabetes Mellitus on Cognitive Aging

Diabetes mellitus type 2 (DMT2), also known as type 2 diabetes or adult-onset diabetes, comprises about 90% of cases of diabetes, with the other 10% due primarily to diabetes mellitus type 1 and gestational diabetes. Long-term complications can include heart disease, strokes, diabetic retinopathy, kidney failure, and poor blood flow in the limbs leading to amputations.

It has been suggested that DMT2 can also negatively affect performance in tests of learning and memory, while other cognitive domains remain preserved. Researchers from Chile and Germany investigated the role of DMT2 on cognitive functioning, drawing on the older of two birth cohorts (1930-1932) from the Interdisciplinary Longitudinal Study of Adult Age.

Extensive psycho-geriatric and neuropsychological examinations were conducted in 322 participants, of whom 109 were diagnosed with mild cognitive impairment (MCI). MCI is an intermediate stage between the expected cognitive decline of normal aging and the more serious decline of dementia. It can involve problems with memory, language, thinking and judgment that are greater than normal age-related changes.

Across all domains, the highest performance was achieved by healthy controls without DMT2, followed by controls with DMT2, MCI patients without DMT2, and MCI patients with DMT2. Repeated measures analyses revealed that performance developed rather steadily in the control participants without DMT2 but decreased for the other diagnostic groups. These effects were particularly pronounced in tasks assessing executive dysfunction rather than amnestic deficits. Their findings substantiate the hypothesis that cognitive decline is aggravated by a comorbid DMT2.