The baseline characteristics of the 37,308 persons who
completed the insomnia questionnaire are shown in table 1
stratified by diagnostic classification. The prevalence rate for
insomnia was 4.4 percent, while a further 5.8 percent of participants
experienced insomnia without impairment. Insomnia
was more prevalent among women and persons with
lower educational levels, and sleep problems increased significantly
with older age. Greater cigarette use and alcohol
intake, and less exercise, were associated with increasing reports
of sleep problems at baseline. Both self-reported somatic
symptoms and diagnosis were strongly associated with
increasing sleep disturbances, as were anxiety and depression
(table 1