Season and outdoor temperature in relation to detection and control of hypertension in a large rural Chinese population.

Yijian Qian,Zheng Bian,Huaidong Du,Liming Li,Lingli Chen,Xinwei Zhang,Yaping Chen,Min Yu,Danting Su,Yu Guo,Zhengming Chen

doi:10.1093/ije/dyu158

Abstract

Background: In many Western populations, blood pressure varies moderately with season and outdoor temperature. Relatively little is known about effects of seasonal changes in blood pressure on the detection and control of hypertension in general populations, especially in low- and middle-income countries.Methods: We analysed cross-sectional data of 57 375 (42% men) participants aged 30–79 (mean 52.3) years who were enrolled during 2004–08, as part of the China Kadoorie Biobank, from a rural county in the south-east costal Zhejiang Province. Analyses related daily mean outdoor temperature, obtained from local Meteorological Bureau, to mean systolic (SBP) and diastolic blood pressure (DBP), rate of newly detected hypertension and, among those with self-reported physician-diagnosed hypertension, rate of adequate blood pressure control, using multiple linear and logistic regression models.Results: The overall mean blood pressure was 135.9 mmHg for SBP and 80.5 mmHg for DBP. Daily outdoor temperature ranged between −2.9 and 33.7°C, with July being the hottest month (mean 29.4°C) and January the coldest (mean 4.0°C). Comparing January (the coldest month) with July (the warmest), the differences in the adjusted SBP/DBP were 19.2/7.7 mmHg. Each 10°C lower ambient temperature was associated with 6.9/2.9 mmHg higher SBP/DBP,14.1% higher prevalence of newly detected hypertension and, among those with pre-diagnosed hypertension, 13.0% lower hypertension control rate.Conclusion: In rural China, lower outdoor temperature is strongly associated with higher mean blood pressure and hypertension prevalence as well as poorer hypertension control, and should be considered when conducting population-based hypertension surveys and providing treatment for hypertensive patients.

Highlights

Hypertension, or raised blood pressure, is a common, dangerous and treatable condition, but its detection and control remain a major health challenge in many parts of the world, in low- and middle-income countries such as China
To fill in this knowledge gap, we report a detailed analysis of cross-sectional data of over 50 000 adults from a rural coastal area in the south of Yangzi River, from the China Kadoorie Biobank (CKB) study.[6]
Each 10C lower outdoor temperature was associated with 6.9/2.9 mmHg higher systolic blood pressure (SBP)/diastolic blood pressure (DBP), a

Summary

Introduction

Hypertension, or raised blood pressure, is a common, dangerous and treatable condition, but its detection and control remain a major health challenge in many parts of the world, in low- and middle-income countries such as China. In Western populations where most people have good access to adequate housing and health care, mean blood pressure in adults tends to vary only moderately with outdoor temperature.[1,2,3,4] In China, the situation is quite different, with a recent study showing unusually large effects of outdoor temperature on blood pressure.[5] In that study there was a great heterogeneity in the strength of the association across different regions of China, reflecting differences in local climates and in housing conditions (e.g. access to central heating) and other known determinants of blood pressure (e.g. age, adiposity, alcohol drinking).[5] Despite these findings, questions remain about the patterns and correlates of seasonal changes of blood pressure in specific regions of China, especially in rural areas where no proper household heating during winter is available, and about their relevance for detection and control of hypertension in the general population. Each 10C lower ambient temperature was associated with 6.9/2.9 mmHg

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