“My blood pressure is low today, do you have the heating on?” The association between indoor temperature and blood pressure

OBJECTIVES: The independent association of indoor temperature with blood pressure (BP) is poorly understood and is not routinely considered in hypertension diagnosis or research. Questions remain as to whether the effect of indoor temperature on BP is confounded or modified by other factors. METHODS: This study used data from the Health Survey for England 2014, consisting of 4659 community-dwelling adults aged 16 years and over, interviewed from January to December. Multivariable regression models were used to determine whether indoor temperature was related to levels of BP, and whether these relationships were confounded by other factors, including mean monthly outdoor temperature. RESULTS: After controlling for confounding variables, a 1°C decrease in indoor temperature was associated with rises of 0.48 mmHg (95% confidence interval: −0.72 to −0.25) in SBP and 0.45 mmHg (95% confidence interval: −0.63 to −0.27) in DBP. The magnitude of association of indoor temperature with DBP and SBP was modified by physical activity. The indoor temperature–BP relationship was stronger in people who do not take physical activity regularly than people who exercise regularly. CONCLUSION: The size of the independent association between indoor temperature and BP suggests it should be considered in the clinical management of hypertension and in hypertension research. Room temperature should also be considered as a modifiable risk factor in hypertension-related mortality and morbidity