title: Association between short total sleep time and hypertension:  the Skara Sleep Cohort.
abstract: OBJECTIVE
  Apnea hypopnea index (AHI) is used to study the association between obstructive sleep apnea (OSA) and hypertension, but the independent contributions of total sleep time (TST) and apnea/hypopnea event count to hypertension have not been previously investigated. We studied the relationship between polysomnographically assessed TST and hypertension in a sex-balanced community-dwelling cohort of hypertensive patients and normotensive controls (Skara Sleep Cohort).
  
  
  METHODS
  Participants (n = 344, men 173, age 61.2 ± 6.5 years, BMI 28.6 ± 4.8 kg/m, mean ± SD) underwent ambulatory home polysomnography. Hypertension was defined according to contemporary Swedish national guidelines. A multivariate logistic regression model was used to predict hypertension status from TST and apnea/hypopnea count (total events/night) adjusting for sex, age and BMI.
  
  
  RESULTS
  OSA was highly prevalent in this population (AHI 26 ± 4 events/h). Hypertensive patients had shorter TST than normotensive patients (353 ± 81 vs. 389 ± 65 min, P < 0.001), whereas total apnea/hypopnea count did not differ (167 ± 138 vs. 146 ± 148 events/night, P = 0.2). Multivariate logistic regression analysis revealed that short TST was associated with hypertension status [odds ratio 2.0; 95% confidence interval (95% CI) 1.2-3.3; P = 0.0015]. The significant association between apnea/hypopnea count and hypertension status was nonlinear (odds ratio 2.6; 95% CI 1.2-5.8; P = 0.04). The type of antihypertensive treatment was not found to significantly influence TST.
  
  
  CONCLUSIONS
  Short sleep time assessed by polysomnography was associated with hypertension in this community-dwelling population. Short sleep and presence of sleep apnea appear to independently link to hypertension.
authors.affiliation: Center for Sleep and Wake Disorders, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden. zou.ding@lungall.gu.se
authors.forename: Ding
authors.initials: D
authors.lastname: Zou
authors.forename: Derek N
authors.initials: DN
authors.lastname: Eder
authors.forename: Davoud
authors.initials: D
authors.lastname: Eskandari
authors.forename: Ludger
authors.initials: L
authors.lastname: Grote
authors.forename: Kristina Bengtsson
authors.initials: KB
authors.lastname: Boström
authors.forename: Ulf
authors.initials: U
authors.lastname: Lindblad
authors.forename: Jan
authors.initials: J
authors.lastname: Hedner
mesh_terms: D000368:Aged; D015331:Cohort Studies; D006801:Humans; D006973:Hypertension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000150:complications; D013548:Sweden; D013997:Time Factors