Insomnia increases risk for cardiovascular events in women and in men with low socioeconomic status: a longitudinal, register-based study.

OBJECTIVES: Insomnia and short and long sleep durations have all been linked to cardiovascular disease. Male gender and low socioeconomic status are also related to cardiovascular disease, but it is unclear whether these two factors modify the impact of poor sleep on cardiovascular disease incidence.
METHODS: Participants (5875 men and 7742 women ages 45 to 64 with no history of cardiovascular disease from the general population of Malmö, Sweden; participation rate 41%) were enrolled from 1992 to 1994 and followed until 2005 or until the first cardiovascular event (defined as myocardial infarction, stroke, or death due to ischemic heart disease), as recorded by official registers. Baseline blood pressure, BMI, and inquiry data concerning psychosocial circumstances and self-reported sleep habits were compared with hazard ratios (HRs) of cardiovascular events.
RESULTS: Affirming 'moderate' or 'considerable' problems with at least one out of the four insomnia symptoms was associated with cardiovascular event in women (fully-adjusted HR 1.4 [95% CI 1.2-1.6] and population attributable fraction 17.3%). The same was true of men with past or present manual occupation (HR 1.3 [95% CI 1.1-1.6] and population attributable fraction 11.8%). The HRs increased further in women where insomnia symptoms were combined with short or long sleep duration.
CONCLUSIONS: Insomnia is a significant public health problem with implications for cardiovascular disease incidence. Taking gender and socioeconomic status into account is a worthwhile approach in research on sleep and cardiovascular disease outcomes.