Seasonal variation in blood pressure and its relationship with outdoor temperature in 10 diverse regions of China: the China Kadoorie Biobank

OBJECTIVES:Mean blood pressure varies moderately with outdoor air temperature in many western populations. Substantial uncertainty exists, however, about the strength of the relationship in other populations and its relevance to age, adiposity, medical treatment, climate and housing conditions. METHODS:To investigate the relationship of blood pressure with season and outdoor temperature, we analysed cross-sectional data from the China Kadoorie Biobank study of 506 673 adults aged 30–79 years recruited from 10 diverse urban and rural regions in China. Analyses related mean blood pressure – overall and in various subgroups – to mean local outdoor temperature. RESULTS:The mean difference in SBP between summer (June–August) and winter (December–February) was 10 mmHg overall, and was more extreme, on average, in rural than in urban areas (12 vs. 8 mmHg; P for interaction