Longitudinal changes in sedentary behavior, physical activity and aerobic fitness over 5 years in a cohort at risk for Alzheimer’s disease

Abstract

AbstractBackgroundLow levels of physical activity and aerobic fitness are established modifiable risk factors for Alzheimer’s disease and all‐cause mortality. Work from our group and others has demonstrated significant and positive cross‐sectional relationships between physical activity, aerobic fitness and indicators of brain health (e.g. biomarkers of AD, cognition). The aims of the current study were to determine 5‐year changes in sedentary behavior, physical activity and aerobic fitness in adults at risk for Alzheimer’s disease.MethodThis study enrolled fifty‐seven cognitively unimpaired adults from the Wisconsin Registry for Alzheimer’s Prevention. Participants completed 7 days of physical activity monitoring via accelerometry and a maximal exercise test at two time‐points – 5 years apart. Based on current physical activity guidelines, our chosen measures were time spent engaged in sedentary behavior and moderate‐to‐vigorous physical activity. Aerobic fitness was defined as the highest oxygen consumption (VO2peak, mL/kg/min) value recorded during the final stage of the maximal exercise test when standardized criteria were met. A repeated measures model was used to investigate whether sedentary behavior, physical activity, and aerobic fitness changed over a 5‐year period. Cohen’s d effect sizes and bivariate correlations were used to explore the magnitude of these changes and their relationships with age.ResultAt baseline, participants (mean age at baseline 63.81±6.1) spent 77.86±8.11 hours/week sedentary, engaged in 10.34±4.26 hours/week of physical activity and displayed an aerobic fitness level of 28.26 ±0.99 mL/kg/min. At follow‐up (mean age at follow‐up 68.52±6.1), we observed non‐significant increases in sedentary behavior 2.1% (d=.2; p=.09), and significant declines in physical activity 12.3% (d=.3; p=.01) and aerobic fitness 14.2% (d=1.2; p<.001). Age was negatively associated with 5‐year change in physical activity (r=‐.31; p=.02) but not sedentary behavior (p=.19) or aerobic fitness (p=.80).ConclusionThis study found that physical activity and aerobic fitness significantly declined over a 5‐year period in adults at risk for Alzheimer’s disease, and this decline may accelerate with advancing age. Strategies aimed at promoting physical activity and aerobic fitness (e.g. exercise training) in mid‐late adulthood are warranted. Future studies are needed to test whether changes in sedentary behavior, physical activity, and aerobic fitness are related to brain and cognitive health.