In the January issue of the Archives, we read with great interest the article by Yoder et al.1 In this study, the authors demonstrated that patients' sleep suffers significantly from hospital noise in that they slept significantly less in the hospital relative to home conditions. Furthermore, sleeping in a hospital setting was associated with poorer sleep efficiency (ie, the ratio of time spent asleep to the amount of time spent in bed). These findings are significant in light of previous research indicating that impaired sleep influences measures of general health. For instance, compared with regular sleep, recurrent partial sleep deprivation for 6 days after first exposure to an influenza antigen has been found to impair the early phase of the subsequent adaptive immune response.2 The fact that the detrimental impact of hospital noise on sleep quality may in turn adversely affect recovery from disease underlines the importance of this research, both from a clinical and an economic point of view. However, some important questions require more detailed discussion. Sleep consists of cycles of slow-wave sleep (SWS, also known as deep sleep) and rapid eye movement sleep, alternating in periods of approximately 90 minutes.3 Previous research has shown that beneficial effects of sleep on general health are specifically related to SWS. For instance, a previous study has shown that the amount of SWS predicts insulin sensitivity in response to an intravenous glucose tolerance test the next morning,4 highlighting a critical role of this sleep stage in daytime glucose regulation. Furthermore, the production of antigen-specific antibodies after vaccination against hepatitis A has recently been associated with the amount of SWS activity during the postvaccination night.5 Thus, future research should not only address the influence of hospital noise on sleep quantity (the time spent asleep) but also on sleep architecture (the time spent in each sleep stage).