title: Influence of room heating on ambulatory blood pressure in winter: a randomised controlled study.
abstract: BACKGROUND
  Previous studies have proposed that higher blood pressure (BP) in winter is an important cause of increased mortality from cardiovascular disease during the winter. Some observational and physiological studies have shown that cold exposure increases BP, but evidence from a randomised controlled study assessing the effectiveness of intensive room heating for lowering BP was lacking.
  
  
  OBJECTIVE
  The present study aimed to determine whether intensive room heating in winter decreases ambulatory BP as compared with weak room heating resulting in a 10°C lower target room temperature when sufficient clothing and bedclothes are available.
  
  
  METHODS
  We conducted a parallel group, assessor blinded, simple randomised controlled study with 1:1 allocation among 146 healthy participants in Japan from November 2009 to March 2010. Ambulatory BP was measured while the participants stayed in single experimental rooms from 21:00 to 8:00. During the session, participants could adjust the amount of clothing and bedclothes as required. Compared with the weak room heating group (mean temperature ± SD: 13.9 ± 3.3°C), systolic morning BP (mean BP 2 h after getting out of bed) of the intensive room heating group (24.2 ± 1.7°C) was significantly lower by 5.8 mm Hg (95% CI 2.4 to 9.3). Sleep-trough morning BP surges (morning BP minus lowest night-time BP) in the intensive room heating group were significantly suppressed to about two thirds of the values in the weak room heating group (14.3 vs 21.9 mm Hg; p<0.01).
  
  
  CONCLUSIONS
  Intensive room heating decreased morning BP and the morning BP surge in winter.
authors: Department of Community Health and Epidemiology, Nara Medical University School of Medicine, 840 Shijocho, Kashiharashi, Nara 634-8521, Japan. saekik@naramed-u.ac.jp
authors: Keigo
authors: K
authors: Saeki
authors: Kenji
authors: K
authors: Obayashi
authors: Junko
authors: J
authors: Iwamoto
authors: Yuu
authors: Y
authors: Tanaka
authors: Noriyuki
authors: N
authors: Tanaka
authors: Shota
authors: S
authors: Takata
authors: Hiroko
authors: H
authors: Kubo
authors: Nozomi
authors: N
authors: Okamoto
authors: Kimiko
authors: K
authors: Tomioka
authors: Satoko
authors: S
authors: Nezu
authors: Norio
authors: N
authors: Kurumatani
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D005260:Female; D006361:Heating; D006801:Humans; D006973:Hypertension / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D012621:Seasons; D016037:Single-Blind Method; D055815:Young Adult
keywords: Blood Pressure; Environmental Health; Randomised Trials; Temperature