Relationship between physical activity and biomarkers of pathology and neuroinflammation in preclinical autosomal-dominant Alzheimer's disease

Objective: Physical activity (PA) has been linked to reduced Alzheimer's disease (AD) risk. However, less is known about its effects in the AD preclinical stage. We aimed to investigate whether greater PA was associated with lower plasma biomarkers of AD pathology, neural injury, reactive astrocytes, and better cognition in individuals with autosomal-dominant AD due to the presenilin-1 E280A mutation who are virtually guaranteed to develop dementia. Methods: Twenty-eight cognitively unimpaired mutation carriers (ages x = 29.28) wore a FitBit Charge-4 for 14 days. We calculated their average steps to measure locomotion, and Training Impulse (TRIMP) to quantify the intensity and duration of PAs using heart rate. Plasma amyloid beta 42/40 ratio, phosphorylated tau 181, neurofilament light chain, and glial fibrillary acidic protein (GFAP) were measured. Cognition was assessed with the Consortium to Establish a Registry for Alzheimer's Disease word list learning and delayed recall, Trail Making Test Part A, and Wechsler Adult Intelligence Scale-version IV Digit Span Backward. We conducted multiple linear regressions controlling for age, sex, body mass index, and education. Results: There were no associations among steps or TRIMP with plasma biomarkers or cognition. Greater TRIMP was related to higher GFAP levels. Conclusions: PA was not associated with cognition or plasma biomarkers. However, greater intensity and duration of PAs were related to higher GFAP. Participants engaged very little in moderate to vigorous PA. Therefore, light PA may not exert a significant protective effect in preclinical AD. Future work with larger samples and longitudinal data is needed to elucidate further the potential impact of PA on AD progression in the preclinical stages.