Type 2 Diabetes and Cognitive Dysfunction: Cardiorespiratory Fitness and Physical Activity Matters

Diabetes is associated with an increased risk of cognitive dysfunction. We are aimed at examining cognitive performance in people with Type 2 diabetes mellitus (T2DM) and their correlation with physical activity (PA)/fitness level and mood.

A cross-sectional study involving 47 individuals with T2DM, 30 diabetes-free individuals (controls): ages of 40-65 years and without dementia. Subjects were evaluated using a neuropsychological test battery that included Stroop, VLMT, CORSI, TMT and neuropsychiatric scales. The Global Physical Activity Questionnaire (GPAQ) was assessed. Physical fitness was evaluated using a maximal cardiopulmonary exercise testing (CPX).

Compared with controls, people with T2DM had lower cardiorespiratory fitness (CRF) and more frequent cognitive performance below 1 SD of the normative value. Those individuals with T2DM, who displayed low fitness, showed significantly poorer cognitive inhibition (Stroop, p < 0.001), processing speed (TMT-A, p < 0.001), cognitive flexibility (TMT-B, p < 0.001), visuospatial memory (CORSI, p < 0.001) and memory consolidation (VLMT, p < 0.001). Higher ventilatory and metabolic CRF markers and higher PA levels correlated significantly with higher cognitive performance. None of the neuropsychological or psychiatric background variables correlated significantly with any of the cognitive scales.

Individual CRF markers and PA levels correlated positively with cognitive performance in people with T2DM and in nondiabetic individuals. However, individuals with T2DM showed at least two to three times more frequent cognitive performances more than 1 SD below norm as compared with controls. Among people with T2DM, those with low aerobic fitness/PA levels showed significantly lower cognitive performance, especially in the attention-concentration, executive functioning, episodic memory and visuospatial processing domains.