Most studies on assigned physical activity provided only snapshots of a specific time period and were not reflective of physical activity over the course of a lifetime. For example, associations of physical activity and subclinical brain markers observed at older ages may be subject to reverse causality due to comorbidities, age-related changes in lifestyle, or initial cognitive impairment.
Therefore, there was an unmet need for observational studies with repeat physical activity measures to determine the long-term role of physical activity on brain structure.
