Abstract
IntroductionBlood pressure is a major cause of cardiovascular disease (CVD) and both may increase as outdoor temperatures fall. However, there are still limited data about seasonal variation in blood pressure and CVD mortality among patients with prior-CVD.MethodsWe analysed data on 23 000 individuals with prior-CVD who were recruited from 10 diverse regions into the China Kadoorie Biobank during 2004–8. After 7 years of follow-up, 1484 CVD deaths were recorded. Baseline survey data were used to assess seasonal variation in systolic blood pressure (SBP) and its association with outdoor temperature. Cox regression was used to examine the association of usual SBP with subsequent CVD mortality, and seasonal variation in CVD mortality was assessed by Poisson regression. All analyses were adjusted for age, sex, and region.ResultsMean SBP was significantly higher in winter than in summer (145 vs. 136 mmHg, P < 0.001), especially among those without central heating. Above 5°C, each 10°C lower outdoor temperature was associated with 6.2 mmHg higher SBP. Systolic blood pressure predicted subsequent CVD mortality, with each 10 mmHg higher usual SBP associated with 21% (95% confidence interval: 16–27%) increased risk. Cardiovascular disease mortality varied by season, with 41% (21–63%) higher risk in winter compared with summer.ConclusionAmong adult Chinese with prior-CVD, there is both increased blood pressure and CVD mortality in winter. Careful monitoring and more aggressive blood pressure lowering treatment in the cold months are needed to help reduce the winter excess CVD mortality in high-risk individuals.
Highlights
Blood pressure is a major cause of cardiovascular disease (CVD) and both may increase as outdoor temperatures fall.there are still limited data about seasonal variation in blood pressure and CVD mortality among patients with prior-CVD
Mean systolic blood pressure (SBP) was significantly higher in winter than in summer (145 vs. 136 mmHg, P, 0.001), especially among those without central heating
58C, each 108C lower outdoor temperature was associated with 6.2 mmHg higher
Summary
Blood pressure is a major cause of cardiovascular disease (CVD) and both may increase as outdoor temperatures fall. There are still limited data about seasonal variation in blood pressure and CVD mortality among patients with prior-CVD. There is evidence that outdoor temperature affects blood pressure,[7,8,9] with large effects in China.[8] Exposure to cold temperatures can lead to vasoconstriction and tachycardia, both of which contribute to increased blood pressure and cardiac load.[10] Excess CVD mortality has been reported during the cold seasons,[11,12,13,14,15] part of which may be driven by temperature-related increases in blood pressure. Limited large-scale data exist about seasonal variation in blood pressure and CVD mortality among people with prior-CVD, especially in China where few people have access to central heating in winter and where few people with prior-CVD are properly managed.[16]
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