Hypertension modifies the short-term effects of temperature on morbidity of hemorrhagic stroke

Abstract Background This study estimated the effects of ambient temperature on hospital admissions for hemorrhagic stroke during 2004–2009 in Jinan, China, and the effect modification of hypertension status. Methods The exposure–response relationship between temperature and hemorrhagic stroke was firstly examined, and then the association between daily mean temperature and hemorrhagic stroke was investigated using a generalized additive model. Stratified analyses were conducted to examine the potential effect modification of hypertension. Results A total of 1577 hemorrhagic stroke cases were observed between 2004 and 2009, among which, 1058 were hypertensive and 519 were non-hypertensive. We found an approximately linear relationship between ambient temperature and hemorrhagic stroke. Each 1 °C decrease in the current day's temperature was associated with 1.63% (95% CI: 0.33%, 2.95%) increase in daily hemorrhagic stroke. The stratified analyses observed that the association was significant among hypertensive hemorrhagic stroke, each 1 °C decrease in the current day's temperature was associated with 2.26% (95% CI: 0.57%, 3.98%) increase in daily hypertensive hemorrhagic stroke. While no significant effect was observed for non-hypertensive hemorrhagic stroke. Conclusions Low temperature might be one risk factor for hemorrhagic stroke and hypertension may be one effect modifier of this association in Jinan, China.