title: The effects of midday nap duration on the risk of hypertension in a middle-aged and older Chinese population: a preliminary evidence from the Tongji-Dongfeng Cohort Study, China.
abstract: OBJECTIVE
  Evidence from epidemiological studies suggested that shorter and longer duration of nocturnal sleeping may increase the risk of hypertension for older adults. Little is known about the duration of midday nap on the variability of blood pressure among older adults. In this study, we examined whether duration of habitual midday nap is associated with level of blood pressure or the risk of hypertension in a middle-aged and older Chinese population.
  
  
  METHODS
  A total of 27 009 participants (mean age 63.6 years) from Dongfeng-Tongji Cohort Study received baseline examination including physical examination and laboratory tests, and a face-to-face-interview including demographic information, disease history, and lifestyle. Participants were categorized into five groups according to nap duration, such as no napping, less than 30 min, 30∼60 min, 60∼90 min, and at least 90 min. A series of categorical logistic regression models was used to examine the odd ratios of nap duration with hypertension.
  
  
  RESULTS
  The level of SBP and DBP increased significantly with longer duration of habitual midday napping. Nappers with longer nap duration had considerably higher rate of hypertension. The longer duration of napping was related to higher blood pressure level and was associated with a higher risk of hypertension. After adjusting for possible confounders, the longer duration (>60 min) of napping was still associated with hypertension
  
  
  CONCLUSIONS
  : Our findings showed that the practice of longer afternoon nap is associated with a higher increased risk of hypertension, independent of several covariates. Further prospective researches are needed to examine the midday nap duration for development of hypertension.
authors.affiliation: aMOE Key Lab of Environment and Health bDepartment of Maternal and Child Health cDepartment of Social Medicine, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan dDongfeng General Hospital, Dongfeng Motor Corporation and Hubei University of Medicine, Shiyan, China.
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Cao
authors.forename: Lijun
authors.initials: L
authors.lastname: Shen
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.forename: Handong
authors.initials: H
authors.lastname: Yang
authors.forename: Weimin
authors.initials: W
authors.lastname: Fang
authors.forename: Weihong
authors.initials: W
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Youjie
authors.initials: Y
authors.lastname: Wang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liang
authors.forename: Tangchun
authors.initials: T
authors.lastname: Wu
mesh_terms: D000368:Aged; D044466:Asian People; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology*; D008019:Life Style; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D013997:Time Factors