sleep duration and body mas index

Letter to the Editor Sleep duration and body mass index Sever al report s have recently presente d that there are clear associations between short sleep duration and ele- vated body mass index (BMI) [1–3]. Their study designs are population-based, cross-sectional studies. To clarify whether those relationships also exist in Asian subjects, we conducted re-analysis as follows. We pre viously pre sented the ass ociation between obesit y and hypertensio n or hyper lipidemi a for inhabit- ants in Gunma Prefecture, Japan [4] . Subgroup analyses of 14596 subjects (10016 Women, 4580 men) aged 40–59 years were con duc ted in thi s study. Self-admin ist ere d questionnair es inc luding sle epi ng hours and current smoking habits were used. Subjects’ height and weight were measured with shoes being taken off. Sleep duration was divided into the following subgroups: <6, 6– 6.99, 7–7.99, 8–8.99 and P9 h. Data were analyzed by SPSS for Windows (version 14.0J). One-way ANOVA was conducted to investigate differences in BMI among the five sleep duration groups. Logistic regression analyses using sleep duration as the pre dic tor var iable were per for med for the following three dichotomized criterion of obesity: (1) BMI P 30 versus BMI < 30, (2) BMI P 28 versus BMI < 28, (3) BMI P 25 versus BMI < 25. Gender, age, and current smoking habits were also used for the adjustment of the data. Mean BMI of subjects who sleep less than 6 h was significantly higher than that of subjects who sleep 7– 7.99 h ( p < 0.01). The results from the logistic regressio n analysis showed that sleep durations under 6 h were pos- itively related to women and men having BMI P 30. The prevalence of overweight and obesity in the Japa- nes e pop ula tion, judg ed by BMI P 25, is lower than tha t in US or Eur ope an populations [5]. So we also changed the cut-off value of BMI for logistic regression analysis. When the cut-off value of BMI was changed to 28 or 25, there was no change of significance. In conclusion, short slee p dur atio n was related to high BMI. References [1] Bjorvatn B, Sagen IM, Oyane N, Waage S, Fetveit A, Pallesen S, et al. The association between sleep duration, body mass index and metabolic measures in the Hordaland Health Study. J Sleep Res 2007;16:66–76. [2] Kohatsu ND, Tsai R, Young T, Vangilder R, Burmeister LF, Stromquist AM, et al. Sleep duration and body mass index in a rural population. Arch Intern Med 2006;16 6:1701– 5. [3] Singh M, Dr ake CL, Roehrs T, Hudgel DW, Roth T. The association between obesity and short sleep duration: a population- based study. J Clin Sleep Med 2005;1:357–63. [4] Kawada T. Body mass index is a good predict or of hypertension and hyperlipidemia in a rura l Japanese popu lati on. Int J Obes Relat Metab Disord 2002;26:725–9. [5] Intern ational Obesity Taskforc e. Available from: http://www.iotf. org/database/index.asp. Tomoyuki Kawada * Hirofumi Inagaki Shosuke Suzuki Department of Hygiene and Public Health, Nippo n Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8602, Japan E-mail address: [email protected] Received 9 October 2007; accepted 31 October 2007 Available online 21 February 2008 1389-9457/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.10.014 * Corresponding author. Tel.: +81 3 3822 2131; fax: +81 3 5685 3065. www.elsevier.com/locate/sleep Sleep Medicine 9 (2008) 808

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