Mortality associated with sleep duration and insomnia.
BACKGROUND
Patients often complain about insufficient sleep or chronic insomnia in the belief that they need 8 hours of sleep. Treatment strategies may be guided by what sleep durations predict optimal survival and whether insomnia might signal mortality risks.


METHODS
In 1982, the Cancer Prevention Study II of the American Cancer Society asked participants about their sleep duration and frequency of insomnia. Cox proportional hazards survival models were computed to determine whether sleep duration or frequency of insomnia was associated with excess mortality up to 1988, controlling simultaneously for demographics, habits, health factors, and use of various medications.


RESULTS
Participants were more than 1.1 million men and women from 30 to 102 years of age. The best survival was found among those who slept 7 hours per night. Participants who reported sleeping 8 hours or more experienced significantly increased mortality hazard, as did those who slept 6 hours or less. The increased risk exceeded 15% for those reporting more than 8.5 hours sleep or less than 3.5 or 4.5 hours. In contrast, reports of "insomnia" were not associated with excess mortality hazard. As previously described, prescription sleeping pill use was associated with significantly increased mortality after control for reported sleep durations and insomnia.


CONCLUSIONS
Patients can be reassured that short sleep and insomnia seem associated with little risk distinct from comorbidities. Slight risks associated with 8 or more hours of sleep and sleeping pill use need further study. Causality is unproven.
Kripke
Daniel F
DF
Department of Psychiatry 0667, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0667, USA. DKripke@UCSD.edu
Garfinkel
Lawrence
L
Wingard
Deborah L
DL
Klauber
Melville R
MR
Marler
Matthew R
MR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002423:Cause of Death; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012306:Risk; D012892:Sleep Deprivation / Q000401:mortality*; D007319:Sleep Initiation and Maintenance Disorders / Q000401:mortality*; D020521:Stroke / Q000401:mortality; D015996:Survival Rate; D014481:United States