Poor Sleep, Higher Death Risk Linked
The eight-year study based on 5,614 Sleep Heart Health Study participants found two sleep-stage transition types associated with higher mortality risk.
"In light of this growing body of evidence, people should strive to maintain good sleep habits, such as going to bed and getting up at the same time each day and sleeping for seven to eight hours each night," lead author Alison Laffan, formerly of the Johns Hopkins Bloomberg School of Public Health and now at the California Pacific Medical Center in San Francisco, said in a statement.
Sleep fragmentation was defined using an index of the number of sleep stage transitions per hour of sleep. In addition to a composite transition index, indexes of each of the six types of transitions were also tested.
The relative risk of death as a function of each transition index was calculated using proportional hazards models, adjusting for age, gender, body mass index, race, hypertension, cardiovascular disease, smoking status, respiratory disturbance index and arousal index.
The researchers found two sleep-stage transition types associated with higher mortality risk: wake-to-non-rapid eye movement and non-REM-to-wake.
Brain activity during sleep consists of two basic states -- REM sleep and non-REM sleep. Periods of REM sleep -- about four or five time per night -- total about 90-120 minutes of a night's sleep.