Low Ambient Temperature and Intracerebral Hemorrhage: The INTERACT2 Study

BackgroundRates of acute intracerebral hemorrhage (ICH) increase in winter months but the magnitude of risk is unknown. We aimed to quantify the association of ambient temperature with the risk of ICH in the Intensive Blood Pressure Reduction in Acute Cerebral Haemorrhage Trial (INTERACT2) participants on an hourly timescale.MethodsINTERACT2 was an international, open, blinded endpoint, randomized controlled trial of patients with spontaneous ICH (ResultsLow ambient temperature (≤10°C) was associated with increased risks of ICH: overall cumulative OR was 1.37 (0.99–1.91) for 10°C, 1.92 (1.31–2.81) for 0°C, 3.13 (1.89–5.19) for -10°C, and 5.76 (2.30–14.42) for -20°C, as compared with a reference temperature of 20°C.There was no clear relation of low temperature beyond three hours after exposure. Results were consistent in sensitivity analyses.ConclusionsExposure to low ambient temperature within several hours increases the risk of ICH.Trial RegistrationClinicalTrials.gov NCT00716079