Table 3.

Association between Minutes of Light Activity and Mortality: Isotemporal Substitution Models.

	Model A		Model B		Model C
	HR	95% CI	HR	95% CI	HR	95% CI
Replacing 10 Sedentary Minutes
Light Minutes	0.90	[0.88,0.93]	0.92	[0.89,0.94]	0.91	[0.86,0.96]
Interaction: (Light Minutes)*(years)	1.01	[1.01,1.02]	1.01	[1.00,1.01]	1.01	[1.00,1.03]
MVPA Minutes	0.73	[0.57,0.94]	0.79	[0.63,0.99]	0.70	[0.57,0.85]
P for difference (Light - MVPA)	0.098		0.197		0.012
Replacing 10 MVPA minutes
Light Minutes	1.23	[0.96,1.58]	1.15	[0.92,1.44]	1.30	[1.06,1.59]
Interaction: (Light Minutes)*(Years)	1.01	[1.01,1.02]	1.01	[1.00,1.01]	1.01	[1.00,1.03]
Sedentary Minutes	1.36	[1.06,1.75]	1.26	[1.01,1.58]	1.43	[1.17,1.74]
P for difference (Light - Sedentary)	<0.001		<0.001		<0.001

Abbreviations: HR, hazard ratio; CI, confidence interval; Light, Light activity (counts per minute 100-2,019), MVPA, moderate to vigorous physical activity (counts per minute > 2,019).

Subjects aged 50 to 79 (last birthday) at baseline; mortality follow-up through 2011 (n=3,029).

Models (A) adjust for baseline age, sex, race/ethnicity, education, and minutes of device wear-time. Models (B) additionally adjust for body mass index (kg/m²), smoking, and the presence of diabetes, coronary heart disease, congestive heart failure, stroke, cancer, and mobility limitation. Model (C) excludes those with prevalent chronic illnesses (diabetes, coronary heart disease, congestive heart failure, stroke, and cancer) or mobility limitations at baseline (n=1,424). Models incorporate sampling weights and complex survey characteristics of NHANES.

P-Values for differences are computed using a t-test of the linear combination β_Light – β_MVPA or β_Light – β_Sed with the null hypothesis that this quantity is zero.