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 reevaluation of how emerging adulthood may affect PA levels and the importance of considering time of day and sex differences when developing PA interventions.

Patterns of sedentary and active time accumulation are associated with mortality in US adults: The NHANES study

“…Sedentary behavior is a significant risk factor for a wide range of chronic diseases, comorbidities, and mortality [1–10]. As people age, sedentary behaviors increase [7,11,12]. However, little is known about the detailed changes in daily sedentary patterns that accompany these shifts.…”

Total volume of physical activity: TAC, TLAC or TAC( λ )

“…We thank Wolff-Hughes and colleagues for their thoughtful response (Wolff-Hughes et al, 2017) to our recently published findings (Varma et al, 2017). Wolff-Hughes et al correctly indicate that our findings, which model physical activity (PA) over the lifespan using total log-transformed activity counts (TLAC) as a proxy measure for total volume of PA, are inconsistent with their findings (Wolff-Hughes et al, 2014; Wolff-Hughes et al, 2015) that use total (non-transformed) activity counts (TAC).…”

“…There is an approximate 10-fold difference in the median daily percent of MVPA compared to LiPA among youth and older adults, and the largest contributor to total PA is LiPA accumulated across the day. Our decision to use TLAC in our paper (Varma et al, 2017) was based partially on this observation. It is important to additionally note that our results showing trends in MVPA across the lifespan very closely match the results from Wolf-Hughes et al showing TAC in youth (Wolff-Hughes et al, 2014) and adults (Wolff-Hughes et al., 2015) further indicating TAC may closely approximate MVPA however does not adequately model the contribution of lower intensity PA.…”

“…Our paper (Varma et al, 2017) explored total volume of PA across the lifespan using a summary measure that appropriately reflected LiPA, the major contributor to total accumulated PA across the day. We were able to identify age-related trends in PA and also show the importance of understanding how the allocation of PA across the day may drive those trends.…”

Physical Activity and Adiposity in a Racially Diverse Cohort of US Infants

“…Thus, we had few instances of nonwear time during the 4-day assessment period. To reduce skewness in the data and be consistent with prior studies, we log-transformed minute-level activity counts by applying the transformation log(1 + activity counts) (25). We summed the log-transformed activity counts for each minute to obtain daily activity counts, a measure of total volume of physical activity per day.…”