Quantifying the lifetime circadian rhythm of physical activity: a covariate-dependent functional approach.

ABSTRACT: Objective measurement of physical activity using wearable devices such as accelerometers may provide tantalizing new insights into the association between activity and health outcomes. Accelerometers can record quasi-continuous activity information for many days and for hundreds of individuals. For example, in the Baltimore Longitudinal Study on Aging physical activity was recorded every minute for [Formula: see text] adults for an average of [Formula: see text] days per adult. An important scientific problem is to separate and quantify the systematic and random circadian patterns of physical activity as functions of time of day, age, and gender. To capture the systematic circadian pattern, we introduce a practical bivariate smoother and two crucial innovations: (i) estimating the smoothin

SUBMITTER: Xiao L 

PROVIDER: S-EPMC4804116 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature