title: Environmental ambient temperature and blood pressure in adults: A systematic review and meta-analysis.
abstract: OBJECTIVE
  Although many individual studies have examined the association between temperature and blood pressure (BP), they used different methods and also their results were somewhat inconsistent. The aims of this study are to quantitatively summarize previous studies and to systematically assess the methodological issues to make recommendations for future research.
  
  
  METHODS
  We searched relevant empirical studies published before January 2016 concerning temperature and BP among adults using the MEDLINE, Embase and PubMed databases. Mean changes in systolic (SBP) and diastolic blood pressure (DBP) per 1°C reduction in temperature were pooled using a random-effects meta-analysis.
  
  
  RESULTS
  Of 23 studies included, 14 were used for meta-analysis. Consistent, statistically significant, inverse associations were observed between ambient temperature (mean, maximum, minimum outdoor temperature and indoor temperature) and BP. An 1°C decrease in mean daily outdoor temperature was associated with an increase in SBP and DBP of 0.26mmHg (95% CI: 0.18-0.33) and 0.13 (95% CI: 0.11-0.16), respectively. The increase was greater in people with conditions related to cardiovascular disease. An 1°C decrease in indoor temperature was associated with 0.38mmHg (0.18-0.58) increase in SBP, while the effects on DBP were not estimated due to limited studies. Among the previous studies on temperature-BP relationship, temperature and BP measurements are not accurate enough and statistical methods need to be improved.
  
  
  CONCLUSIONS
  Lower ambient temperatures seem to increase adults' BP and people with conditions related to cardiovascular disease are more susceptible to drops in temperature. Indoor temperature appeared to have a stronger effect on BP than outdoor temperature. To understand temperature-BP relationship well, a study combining repeated personal temperature exposure and ambulatory BP monitoring, applying improved statistical methods to examine potential non-linear relationship is warranted.
authors.affiliation: Department of Health Policy and Management, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China; Guangzhou Key Laboratory of Environmental Pollution and Health Risk Assessment, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Health Policy and Management, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China; Guangzhou Key Laboratory of Environmental Pollution and Health Risk Assessment, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China.
authors.forename: Changchang
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Chronic Disease Prevention, Bao'an Hospital for Chronic Disease Prevention and Treatment, 99 Wenwei Road, Shenzhen 518101, China.
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: School of Public Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Brisbane, Queensland 4059, Australia.
authors.forename: Adrian G
authors.initials: AG
authors.lastname: Barnett
authors.affiliation: School of Public Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Brisbane, Queensland 4059, Australia.
authors.forename: Shilu
authors.initials: S
authors.lastname: Tong
authors.affiliation: Center for Environment and Population Health, School of Environment, Griffith University, 170 Kessels Road, Brisbane, Queensland 4111, Australia.
authors.forename: Dung
authors.initials: D
authors.lastname: Phung
authors.affiliation: Center for Environment and Population Health, School of Environment, Griffith University, 170 Kessels Road, Brisbane, Queensland 4111, Australia.
authors.forename: Cordia
authors.initials: C
authors.lastname: Chu
authors.affiliation: Global Health Research Center, Duke Kunshan University, Kunshan, Jiangsu 215316, China.
authors.forename: Keith
authors.initials: K
authors.lastname: Dear
authors.affiliation: School of Atmospheric Sciences, Sun Yat-sen University, 135 Xingang Xi Road, Guangzhou 510275, China. Electronic address: eeswxm@mail.sysu.edu.cn.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Health Policy and Management, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China; Guangzhou Key Laboratory of Environmental Pollution and Health Risk Assessment, School of Public Health, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China; Center for Environment and Population Health, School of Environment, Griffith University, 170 Kessels Road, Brisbane, Queensland 4111, Australia. Electronic address: huangcr@mail.sysu.edu.cn.
authors.forename: Cunrui
authors.initials: C
authors.lastname: Huang
mesh_terms: D000328:Adult; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D002318:Cardiovascular Diseases / Q000453:epidemiology; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D013696:Temperature
keywords: Cardiovascular disease; Mechanism; Meta-analysis; Meteorological factors; Methodology