Table 2.

Associations of physical activity and sleep patterns with season. Data from 669 participants, age 12–14 years, in Project Viva.

	Winter	Spring	Summer	Autumn	Global
		β (95% CI)			p-value
Sleep duration (min/night)	0.0 (ref)	−2.9 (−12.0, 6.2)	0.5 (−8.5, 9.4)	−9.4 (−18.8, 0.0)	0.15
Sleep midpoint time (min)	0.0 (ref)	−28 (−41, −14)	41 (27, 54)	−29 (−43, −15)	<.001
Wake after sleep onset (min)	0.0 (ref)	−5.5 (−10.5, −0.5)	5.9 (1.0, 10.8)	−2.1 (−7.2, 3.0)	<.001
Sleep efficiency (%)	0.0 (ref)	1.0 (0.1, 1.8)	−0.8 (−1.7, 0.0)	0.3 (−0.6, 1.2)	<.001
Total physical activity (cpm)	0.0 (ref)	140 (42, 238)	181 (84, 277)	126 (24, 227)	0.002
Light-to-moderate PA (hrs/week), self-report	0.0 (ref)	1.6 (0.6, 2.6)	2.3 (1.3, 3.3)	0.5 (−0.5, 1.5)	<.001
Vigorous PA (hrs/week), self-report	0.0 (ref)	1.0 (0.0, 1.9)	0.9 (0.0, 1.8)	1.0 (0.0, 2.0)	0.12

Linear regression models adjusted for maternal education status, household income, and child race/ethnicity, sex, age, BMI z-score and pubertal development scale. Abbreviations: β=effect estimate; CI=confidence interval.