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We are grateful to the author for his interest in our paper.1Khan H Kella D Kunutsor SK Savonen K Laukkanen JA Sleep duration and risk of fatal coronary heart disease, sudden cardiac death, cancer death and all-cause mortality.Am J Med. 2018; https://doi.org/10.1016/j.amjmed.2018.07.010Abstract Full Text Full Text PDF Scopus (15) Google Scholar Studies have so far reported a non-linear, almost J-shaped relationship of sleep duration with cardiovascular mortality.2Liu TZ Xu C Rota M et al.Sleep duration and risk of all-cause mortality: A flexible, non-linear, meta-regression of 40 prospective cohort studies.Sleep Med Rev. 2017; 32: 28-36Crossref PubMed Scopus (16) Google Scholar, 3Cappuccio FP D'Elia L Strazzullo P Miller MA Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies.Sleep. 2010; 33: 585-592Crossref PubMed Scopus (669) Google Scholar We have extended these findings by ascertaining the relationship of sleep duration with cause specific mortality in a large prospective cohort. A limitation with the existing data on sleep includes poor characterization of the sleep exposure, as a self-reported measure of sleep duration is used. In addition, it does not inform us about the nocturnal vs. diurnal timing of the sleep. We agree that sleep quality, measured objectively, would add more to the relationship of sleep with health outcomes and quality of life. In addition, as the author reports, insomnia or poor sleep is an entity that has been independently associated with cardiovascular disease.4Bertisch SM Pollock BD Mittleman MA et al.Insomnia with objective short sleep duration and risk of incident cardiovascular disease and all-cause mortality: Sleep Heart Health Study.Sleep. 2018; 41Crossref PubMed Scopus (168) Google Scholar Insomnia can be a pathological condition and be associated with existing comorbid illness,5Prather AA Vogelzangs N Penninx BW Sleep duration, insomnia, and markers of systemic inflammation: results from the Netherlands Study of Depression and Anxiety (NESDA).J Psychiatr Res. 2015; 60: 95-102Crossref PubMed Scopus (81) Google Scholar or it may become part of one's life-style. This may happen in some industries and work cultures where extremely demanding work schedules or night shift work may not allow good sleep hygiene. In such environments, napping is common practice and even encouraged by employers. In some societies, napping is culturally acceptable, such as Japan, where it is referred to as “inemuri” and may even be a subtle sign of diligence. Sleep quality, insomnia symptoms, napping and its effects on health outcomes, and mortality warrant further investigation. Sleep Duration and MortalityThe American Journal of MedicineVol. 132Issue 1PreviewI read the paper by Khan et al1 with great interest. The authors conducted a long-term survival study to evaluate the relationship between self-reported sleep duration and risk of fatal coronary heart disease, sudden cardiac death, cancer related death and all-cause mortality. Adjusted hazard ratios (HRs) (95% confidence intervals (CIs)) of long sleep duration (> 10 hours) against sleep duration under 8 hours was 1.19 (1.01-1.43) for all-cause mortality, 1.27 (0.88-1.84) for fatal coronary heart disease, 1.20 (0.78-1.86) for sudden cardiac death, and 1.29 (0.92-1.80) for cancer death, respectively. Full-Text PDF