First, we collected some data on the lifestyle of the patients, such as alcohol consumption, sleeping pill use, and types of duties, by asking the participants.3 However, few data that enabled estimating the daily calorie balance or dietary habits were provided. Manual laborers made up a small percentage of the participants because the surveyed company was in a service industry, and we did not take the job type into consideration. It may require great efforts to collect such data in detail in an epidemiologic survey, but it would be important in a further study. Second, we used the blood sample data from the health examination to evaluate the metabolic states biochemically. Inflammation markers and adipokines are generally not measured in routine blood examination, so we could not investigate the associations of these markers with lipid metabolism in this study design. Finally, there is no doubt that polysomnography is the best method to assess sleep efficiency and sleep architecture. However, we wanted to assess sleep under usual lifestyle conditions. It is considered that actigraphy provides an acceptably accurate estimate of sleep patterns in normal, healthy adult populations,4 and the unattended type 3 monitoring was reported to be reliable under the specific conditions in which our study was conducted.5 In addition, as we previously reported, interscorer and night-to-night reliability of respiratory disturbance index were excellent3 (interclass correlation coefficient of 0.98 and 0.95, respectively). It remains unsolved whether polysomnography in the laboratory or a portable system in the usual lifestyle conditions is better.