Re-evaluating the effect of age on physical activity over the lifespan

Abstract

Advancements in accelerometer analytic and visualization techniques allow researchers to more precisely identify and compare critical periods of physical activity (PA) decline by age across the lifespan, and describe how daily PA patterns may vary across age groups. We used accelerometer data from the 2003-2006 cohorts of the National Health and Nutrition Examination Survey (NHANES) (n=12,529) to quantify total PA as well as PA by intensity across the lifespan using sex-stratified, age specific percentile curves constructed using generalized additive models. We additionally estimated minute-to-minute diurnal PA using smoothed bivariate surfaces. We found that from childhood to adolescence (ages 6-19) across sex, PA is sharply lower by age partially due to a later initiation of morning PA. Total PA levels, at age 19 are comparable to levels at age 60. Contrary to prior evidence, during young adulthood (ages 20-30) total and light intensity PA increases by age and then stabilizes during midlife (ages 31-59) partially due to an earlier initiation of morning PA. We additionally found that males compared to females have an earlier lowering in PA by age at midlife and lower total PA, higher sedentary behavior, and lower light intensity PA in older adulthood; these trends seem to be driven by lower PA in the afternoon compared to females. Our results suggest a re-evaluation of how emerging adulthood may affect PA levels and the importance of considering time of day and sex differences when developing PA interventions.

Keywords: Accelerometer; Diurnal; Gender; Lifespan; NHANES; Physical activity; Sex differences.

Figure 1

Percentiles of TLAC over the lifespan (6 years old to 84 years old) for males (left) and females (right). TLAC = total log-transformed activity counts Percentiles of TLAC, from 5%-95%, are indicated using different colors (black = 95%, gray = 90%, yellow = 75%, purple = 50%, cyan = 25%, blue = 10%, green = 5%).

Figure 2

Percentile Curves of Sedentary, Light, and Moderate-to-Vigorous PA over the lifespan (6 years old to 84 years old) for males (left) and females (right) Percentiles of SePA, LiPA, and MVPA, from 5%-95%, are indicated using different colors(black = 95%, gray = 90%, yellow = 75%, purple = 50%, cyan = 25%, blue = 10%, green = 5%).

Figure 3

The diurnal distribution of LAC over the lifespan (6 years old to 84 years old) for males (top left), females (top right) and the difference between males and females (bottom). LAC = log-transformed activity counts The diurnal distribution of LAC is represented by a surface with time of day as the horizontal dimension and age as the vertical dimension. Dark blue and dark red colors correspond to lower and higher levels of PA, respectively.