Morbidity associated with sleep disorders in primary care: a longitudinal cohort study

Few epidemiologic studies evaluate the relative contribution of different risk factors on sleep problems. The aim of the present study was to assess demographics, comorbid characteristics, and health outcomes in patients with sleep disorders.

A population-based cohort study with nested case-control analysis was conducted in adults using the U.K. General Practice Research Database. Information was collected for 12,437 patients with a new sleep disorder diagnosis during the year 1996 and 18,350 age- and sex-matched controls. Logistic regression analysis was used to compute odds ratios (OR) and 95% confidence intervals (CI).

The incidence of a new sleep disorder diagnosis was 12.5 per 1000 person-years. There was a clear association of sleep disorders with smoking and excessive alcohol consumption; prior psychiatric disorders, including stress (OR = 3.6, 95% CI = 2.9 to 4.4) and depression (OR = 3.1, 95% CI = 2.8 to 3.3); prior circulatory diseases, including heart failure (OR = 1.8, 95% CI = 1.4 to 2.2) and coronary heart disease (OR = 1.4, 95% CI = 1.2 to 1.6); and prior gastrointestinal diseases, including gastroesopha-geal reflux disease (OR = 1.4, 95% CI = 1.2 to 1.7) and irritable bowel syndrome (OR = 1.5, 95% CI = 1.2 to 1.9). Use of hypnotics and anti-depressants was increased in the year after diagnosis. Relative 1-year mortality risk was 3-fold higher in the sleep disorder group than in controls, with a noticeably higher proportion of deaths due to suicide.

The fact that sleep disorders were associated with several morbidities, most strongly with psychiatric disorders as well as with increased mortality, underscores the importance of sleep problems as indicators of health status.