Study objective: To examine the effects of daytime rest without sleep and duration of the siesta on mortality.
Design: Longitudinal observation.
Setting and participants: Population sample of 442 community-dwelling 70-year-old subjects examined both at home and in a geriatric hospital.
Interventions: N/A.
Measurements and results: Overall mortality for those who neither rested nor slept was 9.3%, for those who rested without sleep 10.9%, and for those who slept 19%, p<0.02. Males had higher mortality (19%) than females (10%), p<0.006. Rest without sleep had no effect on mortality: in males, 13%, 21%, 18% for no rest, rest of less than one hour, or more than one hour with respective 8%, 6% and 4% in females. However, daytime sleep in males of more than one hour had 28.2% mortality, whereas sleep of one hour or less had 13.6% mortality, p=0.02. In females mortality rate was not different by sleep duration: 16% and 13.6% for those who slept for one hour or less, or more than one hour, respectively. In a multivariate analysis in females, a siesta of one hour or less was associated with risk odds ratio (ROR) of 4.67 and 95% confidence interval (CI) 1.22-17.80 and of one to two hours, ROR was 5.57 and 95% CI 1.05-29.49. For males, siesta of less than one hour was not associated with excess risk, ROR 0.9 and 95% CI 0.39-2.38; a siesta of one to two hours with ROR of 2.61 and 95% CI 1.01-6.80; and two hours or more ROR 13.6 and 95% CI 0.98-2.10.
Conclusions: Rest without sleep is not associated with excess risk of mortality. However, siesta of one to two hours is associated with increased mortality in males whereas, in women, a siesta of less than one hours confers the excess risk.