Effects of indoor and outdoor temperatures on blood pressure and central hemodynamics in a wintertime panel of peri-urban Chinese adults

Abstract

BACKGROUND AND AIM: Excess wintertime cardiovascular mortality has been observed in populations globally and is partly attributed to cold-induced elevated blood pressure (BP). An inverse relationship between outdoor temperature and BP is well documented. The influence of indoor environmental conditions (e.g., heating, insulation) and indoor temperature on BP is less clear. We examined the effects of indoor and outdoor temperature on wintertime BP and central hemodynamics among older adults in peri-urban Beijing, China. METHODS: We enrolled 1,285 older adults into a panel study conducted in two winter seasons (2018-19 and 2019-2020). Staff traveled to participant homes to administer a questionnaire and measure their brachial and central systolic and diastolic BPs, pulse pressures, and pulse pressure amplification. Indoor temperature was measured within the 5-minutes prior to BP measurements for all participants and 12-month indoor temperature measurements were obtained in a 37% (1st season) and 32% (2nd season) random subsample. Village-level outdoor temperature was estimated from regional meteorological stations. Multivariable mixed-effects regression models were used to estimate the within- and between-individual effects of indoor and outdoor temperature on BP, allowing for effect measure modification. RESULTS:Indoor and outdoor winter temperatures ranged from 0.0 to 28.0˚C and -14.3 to 6.4˚C, respectively. Those in colder homes had a lower wealth score and less home insulation. We observed an inverse linear relationship between indoor temperature and BP (mmHg per 1˚C increase in temperature: −0.4 to −0.5 systolic, −0.3 diastolic, and −0.2 pulse pressure). We found little evidence of any effect of outdoor temperature with BP, or that outdoor temperature modified the effect of indoor temperature. CONCLUSIONS:We found an inverse association between indoor temperature and BP, but no relationship of BP with outdoor temperature. This suggests a stronger effect on BP of indoor compared to outdoor temperature. Improving insulation and household heating may help lower BP and prevent excess winter mortality. KEYWORDS: Cardiovascular diseases, Epidemiology, Socio-economic factors, Temperature