To the Editor: In their cohort study assessing the relationship between sleep duration and incident coronary artery calcification, Mr King and colleagues1 reported an association between longer sleep duration and reduced incidence of coronary artery calcification. The proportion of individuals who developed coronary calcification was markedly greater among participants with actigraphy measurements indicating sleep duration of less than 4 hours per night (measured for 6 nights for each participant).
Vichayavilas P, Kelly C. Relationship Between Sleep Duration and Incident Coronary Artery Calcification. JAMA. 2009;301(18):1879-1880. doi:10.1001/jama.2009.631