title: Stronger association of indoor temperature than outdoor temperature with blood pressure in colder months.
abstract: BACKGROUND
  Higher cardiovascular mortality in winter may be partly explained by increased blood pressure (BP) because of cold exposure. However, this winter excess mortality is higher in countries with moderate winter than those with severe winter climate.
  
  
  OBJECTIVE
  Although higher BP in low outdoor temperatures has been reported, the magnitude of association of indoor temperature with ambulatory BP remained unclear. We aimed to compare the associations of indoor and outdoor temperature with ambulatory BP.
  
  
  METHODS
  From repeated measurements on two consecutive days during colder months (October-April) among 868 elderly individuals, we assessed the association of indoor and outdoor temperatures with ambulatory BP using multilevel analysis with random intercept for each individual.
  
  
  RESULTS
  Correlation between indoor and outdoor temperature got weak along with decreasing outdoor temperature. Outdoor temperature was not significantly associated with ambulatory BP. In contrast, a 1°C lower indoor temperature was significantly associated with 0.22 mmHg higher daytime SBP, 0.18% higher nocturnal BP fall, 0.34 mmHg higher sleep-trough morning BP surge independent of potential confounders including physical activity. The models with indoor temperature showed better fit of the model than those with outdoor temperature. Night-time SBP did not show significant association with indoor and outdoor temperature but with bed temperature.
  
  
  CONCLUSIONS
  Our results suggest the importance to assess the association of indoor temperature with cardiovascular mortality to determine whether improving housing thermal environment reduces winter excess mortality.
  
  
  CONCLUSIONS
  Indoor temperature showed stronger association than outdoor temperature with BP in colder months.
authors.affiliation: aDepartment of Community Health and Epidemiology, Nara Medical University School of Medicine bDepartment of Nursing, Tenri Healthcare University cCenter for Academic Industrial and Governmental Relations, Nara Medical University School of Medicine, Nara, Japan.
authors.forename: Keigo
authors.initials: K
authors.lastname: Saeki
authors.forename: Kenji
authors.initials: K
authors.lastname: Obayashi
authors.forename: Junko
authors.initials: J
authors.lastname: Iwamoto
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tone
authors.forename: Nozomi
authors.initials: N
authors.lastname: Okamoto
authors.forename: Kimiko
authors.initials: K
authors.lastname: Tomioka
authors.forename: Norio
authors.initials: N
authors.lastname: Kurumatani
mesh_terms: D000368:Aged; D001794:Blood Pressure; D005260:Female; D006361:Heating; D006801:Humans; D006973:Hypertension / Q000209:etiology / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013696:Temperature