In Reply: Ms Vichayavilas and Mr Kelly have raised an interesting question about whether heavy caffeine consumption might explain the higher risk of incident coronary artery calcification among those with shorter measured sleep duration. We are able to investigate the role of caffeine in our study. In the Coronary Artery Risk Development in Young Adults (CARDIA) year-20 examination, which was the follow-up examination in our ancillary sleep study, detailed diet data were collected using an interviewer-administered quantitative food-frequency questionnaire,1 assisted by plastic food models and food estimation tools such as measuring cups. Average daily caffeine intake was estimated using the nutrient database developed by the Nutrition Coordinating Center at the University of Minnesota (version 36).
Lauderdale DS, King CR, Liu K. Relationship Between Sleep Duration and Incident Coronary Artery Calcification—Reply. JAMA. 2009;301(18):1879-1880. doi:10.1001/jama.2009.632