In an excellent study, Eguchi et al show that short sleep duration (<7.5 hours) is associated with increasing incident cardiovascular disease (CVD) risk, especially when combined with the “riser pattern” (defined when mean systolic blood pressure was higher during sleep than when awake), in Japanese patients.1 Although the data have limitations in relation to polysomnography, snoring, or the use of hypnotics, the study provided an important message about the roles of sleep duration and riser pattern in the higher incidence of CVD such as stroke, fatal or nonfatal myocardial infarction, and sudden cardiac death. However, we did not know the daytime nap duration in this study.
Chang E. The Impact of Daytime Naps on the Relation Between Sleep Duration and Cardiovascular Events. Arch Intern Med. 2009;169(7):717. doi:10.1001/archinternmed.2009.29