Variation in Actigraphy-Estimated Rest-Activity Patterns by Demographic Factors : Rest-Activity Patterns in Adults and Children

Abstract

Rest-activity patterns provide an indication of circadian rhythmicity in the free-living setting. We aimed to describe the distributions of rest-activity patterns in a sample of adults and children across demographic variables. A sample of adults (N=590) and children (N=58) wore an actigraph on their non-dominant wrist for 7 days and nights. We generated rest-activity patterns from cosinor analysis (MESOR, acrophase and magnitude) and non-parametric circadian rhythm analysis (IS: intradaily stability; IV: interdaily variability; L5: least active 5-hour period; M10: most active 10-hour period; and RA: relative amplitude). Demographic variables included age, sex, race, education, marital status, and income. Linear mixed effects models were used to test for demographic differences in rest-activity patterns. Adolescents, compared to younger children, had: 1) later M10 midpoints (β=1.12 hours [95% CI: 0.43, 1.18] and lower M10 activity levels; 2) later L5 midpoints (β=1.6 hours [95% CI: 0.9, 2.3]) and lower L5 activity levels; 3) less regular rest-activity patterns (lower IS and higher IV); and 4) lower magnitudes (β=−0.95 [95% CI: −1.28, −0.63]) and relative amplitudes (β=−0.1 [95% CI: −0.14, −0.06]). Mid-to-older adults, compared to younger adults (ages 18 to 29 years), had: 1) earlier M10 midpoints (β=−1.0 hours [95% CI: −1.6, −0.4]; 2) earlier L5 midpoints (β=−0.7 hours [95% CI: −1.2, −0.2]); and 3) more regular rest-activity patterns (higher IS and lower IV). The magnitudes and relative amplitudes were similar across the adult age categories. Sex, race and education level rest-activity differences were also observed. Rest-activity patterns vary across the lifespan, and differ by race, sex and education. Understanding population variation in these patterns provides a foundation for further elucidating the health implications of rest-activity patterns across the lifespan.