Brain pathology is related to total daily physical activity in older adults

To test the hypothesis that brain pathology is associated with total daily physical activity proximate to death in older adults.

We studied brain autopsies from 428 decedents of the Rush Memory and Aging Project. The quantity of all physical activity was measured continuously for up to 10 days with actigraphy (Actical; Philips Healthcare, Bend, OR). Multiple regression analyses controlling for age and sex were used to examine the relation of brain indexes to total daily physical activity and other clinical covariates proximate to death.

Average total daily activity was 1.53 × 10⁵ counts/d (SD 1.14 × 10⁵ counts/d), and mean age at death was 90.6 (SD 6.12) years. Nigral neuronal loss (estimate -0.232, standard error [SE] = 0.070, p = 0.001) and macroinfarcts (estimate -0.266, SE 0.112, p = 0.017) were independently associated with total daily physical activity proximate to death, accounting for an additional 2.4% of the variance of total daily activity. Other postmortem indexes (Alzheimer disease, Lewy bodies, TAR DNA-binding protein 43, hippocampal sclerosis, microinfarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy) were not associated with total daily activity. In 295 cases (70%), we derived a measure of white matter tissue integrity from postmortem brain MRI. This metric accounted for an additional 5.8% of the variance of total daily physical activity when controlling for age, sex, nigral neuronal loss, and macroinfarcts.

Macroinfarcts, nigral neuronal loss, and white matter pathologies are related to total daily physical activity in older adults, but further studies are needed to explain its pathologic basis more fully.