Sleep in women: Normal values for sleep stages and position and the effect of age, obesity, sleep apnea, smoking, alcohol and hypertension.

OBJECTIVES: To define normal values for total sleep time, sleep latency, sleep efficiency, sleep stages and sleeping positions in women and to investigate how sleep is affected by age, obesity, sleep apnea, smoking, alcohol dependency and hypertension.
METHODS: In a population-based study, 400 Swedish women aged 20-70 years with over-sampling of snorers were investigated using overnight in-home polysomnography. All results are weighted.
RESULTS: The mean normal total sleep time was 392 min, sleep latency 22 min and sleep efficiency 82%. Women spent 31 min in sleep stage 1, 244 min in stage 2, 41 min in stage 3/4 and 76 min in rapid eye movement (REM) sleep. They spent 41% of their sleep time in the supine position, 50% in the lateral position and 9% in the prone position. Multivariate analyses revealed that sleep efficiency was lower in older women and in women with hypertension. Sleep latency was short in women with severe sleep apnea and long in smokers, alcohol-dependent and hypertensive women. Sleep stage 3/4 was inversely related to age and body mass index. Less REM sleep occurred in alcohol-dependent women. Women younger than 45 years old slept a mean of 42% in the lateral position while women of 45 years and older slept 57% in the lateral position (p<0.001).
CONCLUSIONS: In this population-based study of women, we present normal values for sleep stages and sleeping position. We conclude that age, body mass index, obstructive sleep apnea, smoking, alcohol and hypertension reduce sleep quality. With age, women spend more time sleeping in the lateral position.