– Andreas Stang; Nico Dragano; Charles Poole; Susanne Moebus; Stefan Möhlenkamp; Axel Schmermund; Johannes Siegrist; Raimund Erbel; Karl-Heinz Jöckel
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.
Overall, 325 subjects aged 45-74 years (7%) had a history of CAD. Table 1 presents sleep characteristics of participants without a history of CAD. The median sleep duration at night did not vary by age and sex, but elderly women more often tended to sleep <6 hours per night than elderly men. The prevalence of all nocturnal sleep disturbances was considerably higher among women than among men, regardless of age. The most frequently reported regular sleep disturbance among men and women was difficulty maintaining asleep at night among both. The prevalence of the 3 major types of nocturnal sleep disturbances increased monotonically with age among women. The prevalence of daily siesta was slightly higher among men than women, regardless of age. The median duration of siesta among daily siesta takers was particularly long in older men, among whom siestas contributed appreciably to the total daily sleep duration.
Table 2 presents the sleep characteristics of the 325 participants with a history of CAD. Because only 68 women had manifest CAD, age-specific estimates of sleep characteristics in that group are not shown. Women with CAD had a considerably higher prevalence of excessively short sleep durations (<6 h) than men with CAD. Difficulty falling asleep and early morning arousal were more prevalent among women than men, whereas the prevalence of difficulty maintaining sleep was about the same in the 2 sexes. Generally, prevalence of siesta and of nocturnal sleep disturbances were higher among participants who had CAD than among those who did not.
Poor self-perceived health status, depressive mood, difficulties falling asleep, and excessively short nocturnal sleep durations were positively associated with daily long siestas among both men and women. Early morning awakening was negatively associated with regular siesta among men and positively associated with regular siesta among women (Table 3).
Participants taking short daily siestas showed prevalence of CAD risk factors similar to those of participants who took siestas no more than occasionally (Table 4). Participants taking daily long siestas, however, showed higher prevalence of CAD risk factors, and, especially in men, higher prevalence of subclinical atherosclerosis as measured by ABI and EBT. The overall number of established CAD risk factors was higher among subjects taking daily long siestas compared with subjects taking daily short siestas, irregular siestas, or no siestas.
In a hypothetical follow-up study of a cohort with the risk factor distributions of the 3 siesta groups in the Heinz Nixdorf Recall Study, the estimated rate ratios for the association between baseline siesta and incident CAD are appreciably confounded upon adjustment for few or no risk factors, among both men and women (Table 5). The adjusted estimates move closer to the hypothetically unconfounded null value upon adjustment for additional numbers of risk factors. (weiter…)