Researchers here note a correlation between greater exercise in late life and reduced risk of progressing from mild cognitive impairment to dementia. As is the case for most human data, causation cannot be shown, but animal data on the benefits of exercise are unambiguous. It seems safe to suggest that human physiology works much the same way, and that the correlation exists because exercise provides benefits that slow down processes of age-related neurodegeneration.
Physical activity has been suggested to prevent the conversion of mild cognitive impairment (MCI) to dementia in patients. We investigated the association between the continuance and regularity of physical activity and the risk of developing dementia in patients with MCI. We analyzed 6-year followed up data for 247,149 individuals in the National Health Insurance Service (NHIS) cohort of Korea who were enrolled between January 1, 2009, and December 31, 2015.
The patients were divided into four groups: those who did not engage in physical activity consistently (Never-PA group), those who initiated physical activity (Initiation-PA group), those who ceased physical activity (Withdrawal-PA group), and those who performed physical activity consistently (Maintenance-PA group). We also divided the patients into two groups: those who engaged in physical activity irregularly (Irregular-PA) and those who undertook physical activity regularly (Regular-PA).
Our analysis shows that continued physical activity in patients with MCI is associated with a lower risk of dementia of the Alzheimer type (DAT). It appears that the decision to start physical activity leads to a lower risk of DAT, while ceasing physical activity may cause the risk of DAT to increase again. In addition, a higher frequency of physical activity appears to prevent conversion from MCI to DAT (moderate-intensity physical activity more than 5 days per week or vigorous-intensity physical activity more than 3 days per week).
We observed that the Maintenance-PA group had 18% fewer dementia conversions than the Never-PA group, while the Initiation-PA group had 11% less dementia conversion than the Never-PA group. We interpret this to indicate that continuing physical activity occurring at both time points was more effective than initiating a new physical activity between the two time points. Evidence suggests that the longer the duration of physical activity, the greater the effect of physical activity on cognitive function. The findings for the Initiation-PA group may therefore reflect the shorter duration of physical activity compared to the Maintenance-PA group.
There are at least two major mechanisms by which continuous physical activity may prevent the conversion from mild cognitive impairment to dementia. Physical activity increases the expression of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and vascular endothelial growth factor (VEGF). BDNF is important for maintaining neuronal development and for exercise-related improvements in cognitive function. IGF-1 and VFGF play important roles in neurogenesis and angiogenesis and influence the induction of hippocampal BDNF.
Physical activity also increases cerebral blood flow (CBF). After 12 weeks of physical activity, CBF has been shown to increase in the anterior cingulate cortex and hippocampal CBF increased in elderly patients with subjective memory complaints after 16 weeks of physical activity. CBF is thought to maintain cerebral perfusion to help maintain brain volume.