COLORADO SPRINGS — Change in sleep duration during midlife is associated in a U-shaped fashion with risk for death more than a decade later, Dr. Francesco Cappuccio reported at a conference of the American Heart Association.
The major driver of increased mortality among individuals at the low end of the sleep duration continuum is an excess of cardiovascular deaths, while in long sleepers the increase in mortality is due to noncardiovascular causes, according to the results of the Whitehall II study, said Dr. Cappuccio of Warwick Medical School, Coventry, England.
Whitehall II is a prospective cohort study of 10,308 white-collar British civil servants who were 35–55 years old when enrolled in the study in 1985–1988.
The Whitehall II analysis of the impact of changes in sleep duration included data on baseline sleep patterns in 7,729 participants and changes in those patterns over the next 5 years. Participants then were followed for mortality through 2004.
Cardiovascular mortality was 2.4-fold higher among subjects who slept an average of 6–8 hr/night at baseline but cut their sleep duration to 5 hr/night or less over the next 5 years' follow-up, compared with those who held fast to the 6- to 8-hour pattern. The findings held after adjustment for potential confounding factors.
In subjects who increased their sleep duration from 7 to 8 hr/night at baseline to 9 or more, there was an adjusted 2.1-fold increase in noncardiovascular mortality.
Short sleep duration is known to be associated with hypertension, weight gain, and diabetes, all of which increase cardiovascular risk. The relationship between long sleep and increased mortality is unclear. Hypotheses include possible links with depression and cancer-related fatigue, Dr. Cappuccio added.