Table 4.

Nightly Sleep Duration and Risk of Mortality, Stratified on Daily Napping

Type of Death	Nightly Sleep Duration (hours)	Hazard Ratio (95% Confidence Interval) compared to 6–8 hours nightly sleep duration (referent group)*
		Overall Cohort	Did Not Nap Daily	Napped Daily	p-value†
All-cause	< 6	1.02 (0.87–1.19)	0.91 (0.76–1.09)	1.41 (1.00–1.98)	.03
	> 8	1.16 (0.97–1.39)	1.12 (0.92–1.36)	1.29 (0.83–2.02)	.53
Cause-specific
Cardiovascular	< 6	1.03 (0.80–1.31)	0.89 (0.67–1.19)	1.55 (0.91–2.63)	.10
	> 8	1.21 (0.92–1.61)	1.06 (0.76–1.47)	2.05 (1.10–3.83)	.15
Other	< 6	0.91 (0.69–1.19)	0.71 (0.51–0.99)	1.56 (0.93–2.60)	.006
	> 8	1.10 (0.82–1.48)	1.16 (0.85–1.60)	0.64 (0.28–1.47)	.35

^*Adjusted for age; body mass index; history of at least one medical condition including diabetes mellitus, Parkinson’s disease, dementia, chronic obstructive pulmonary disease, non-skin cancer, and osteoarthritis; history of cardiovascular disease; history of hypertension; walks for exercise; alcohol use; smoking status; depression; cognitive impairment; estrogen use; and benzodiazepine use.

^†p-value for daily napping * nightly sleep duration interaction.