Epidemiological aspects of sleep in general public and hospital outpatient samples.

A survey designed to elicit the subjective effect of specific influences on sleep duration and sleep quality was carried out. The sample consisted of 400 individuals selected in a random manner from the general population and a further 400 individuals representing consecutive attenders at the outpatient department of a large teaching hospital. The response rate for the two groups was 97% and 99% respectively. In a question regarding habits which aid in sleep onset, four-fifths of those exercising with a frequency of at least twice per month spontaneously reported exercise as a factor in promoting sleep.