In 2019, 463 million people worldwide were living with the diagnosis diabetes mellitus (DM). It is estimated that the number of people with DM will rise to 700 million by 2045. This is an increase of 37.5%. Diabetes mellitus type 2 (DM2) accounts for about 90% of all DM cases. In addition, epidemiological studies show that DM sufferers have up to 2.5 times the risk of developing affective and cognitive disorders and Alzheimer's disease (AD). The present study investigated the relationship between endurance capacity (ALF) and cognitive function in DM2 patients.
For this purpose 76 subjects were included in the study: 54 DM2 patients with an average age of 58 ± 7 years (29 women, 25 men) and 22 healthy people aged 54 ± 9 years as control group (13 women, 9 men). On four separate examination days, the subjects participated in the study as follows. Day 1: Medical history and initial physical examination. Day 2: Psychological test battery, in which, among other things, executive function was measured using the STROOP test. Day 3: Exercise test on the treadmill to measure ALF and blood pressure. Day 4: Lumbar puncture to collect cerebrospinal fluid (CSF or liquor) to detect neurodegeneration biomarkers (total (t-tau), phosphorylated tau protein (p-tau) and beta-amyloid with 42 amino acids (Aß- 42)).
The main findings of the present study are:
Cognitive performance was significantly worse in DM2 subjects compared to the control group. Temporal information processing in DM2 subjects: 253ms and control group: 174ms. Percentile rank (PR) in DM2 subjects: 15% and control group: 26.5%.
Both systolic and mean arterial pressure (MAD) at rest and under stress were significantly higher in DM2 subjects than in the control group. Systole at rest: DM2 subjects 140mmHg, control group 124mmHg. MAD at rest: DM2 subjects 99mmHg, control group 91mmHg. However, there was no correlation between cognitive performance and blood pressure at rest in either group.
The biomarkers of neurodegeneration were detected in both groups in a non- pathological range. However, p-tau in DM2 subjects with low cognitive performance (DM2<25PR) tended to be elevated compared to DM2 subjects with good cognitive performance (DM2>25PR) and the control group. Beta-amyloid (Aß-42 in pg/ml): DM2<25PR 1302, DM2>25PR 1193, control 1340. Total tau protein (t-tau in pg/ml):
DM2<25PR 354, DM2>25PR 308, control 382 Phosphorylated tau protein (p-tau in
pg/ml): DM2<25PR 48, DM2>25PR 40, control 40.
DM2 patients with below average ALF (DM2-U-ALF) have a similarly poor cognitive
performance as DM2 patients with average ALF (DM2-D-ALF). Temporal information processing for DM2-U-ALF: 246ms, DM2-D-ALF: 263ms.
These results indicate that firstly DM2 leads to cognitive impairment. Secondly, DM2 patients were found to have hypertension, which in turn is a risk factor for the development of cognitive impairment and AD. Furthermore, the influence of ALF on executive function could not be observed in DM2 patients.
With regard to future studies, the relationship between DM2, physical activity and cognitive performance should be examined over a long period of time. This study could be conducted in the context of both endurance and strength training (or a combination of both training stimuli) in DM2 patients to examine whether improved cardiovascular performance in diabetics can counteract cognitive impairment and possibly also the development of Alzheimer's disease.