Daily siesta, cardiovascular risk factors, and measures of subclinical atherosclerosis: results of the Heinz Nixdorf Recall Study.

BACKGROUND: Several studies have assessed the association between siesta and cardiovascular outcomes. Concern exists that confounding might have distorted these results and contributed to discrepancies among them. This report examines the association between siesta habits and cardiovascular risk factors, including sleep disturbances at night, depressed mood, and measures of subclinical atherosclerosis such as coronary calcium score and ankle brachial index.
METHODS: The baseline examination of 4,797 participants aged 45-74 years included interviews, physical examinations, laboratory tests, and electron beam computed tomography. We compared the baseline prevalence of depressed mood, nighttime sleep disturbances, and health status in 3 categories of siesta habits: irregular or no siestas; daily short siestas (1 hour or less); and daily long siestas (>1 hour). We also characterized cardiovascular risk factor distributions in the 3 siesta groups and conducted a sensitivity analysis of the potential for confounding by these factors in studies of incident cardiovascular disease.
RESULTS: Depressed mood and poor self-perceived health status at baseline had positive associations with the age-standardized prevalence of daily long siestas among both men and women. Daily takers of long siestas had a considerably higher prevalence of cardiovascular risk factors in both sexes and appreciably worse measures of subclinical atherosclerosis in men only, in comparison with either of the other siesta groups. Daily long siestas had positive associations with prevalence of several cardiovascular risk factors and measures of subclinical atherosclerosis.
CONCLUSIONS: If uncontrolled, these associations could produce appreciable confounding in studies of siesta habits and incidence of cardiovascular events.