Association between ambient temperature and acute myocardial infarction hospitalisations in Gothenburg, Sweden: 1985-2010

Abstract

Background: Cardiovascular disease (CVD) is the number one cause of death globally and evidence is steadily increasing on the role of non-traditional risk factors such as meteorology and air pollution. Nevertheless, many research gaps remain, such as the association between these non-traditional risk factors and subtypes of CVD, e.g. acute myocardial infarction (AMI). Aims:To investigate the association between daily ambient temperature and AMI hospitalisations in Gothenburg, Sweden (1985-2010). Methods: A case-crossover epidemiological study design was applied. Confounding by PM10, NO2, NOx and O3 was investigated. Susceptible groups by age and sex were explored. The entire year as well as warm (April-September) and cold periods (October -March) were considered. Results:In total 28 215 AMI hospitalisations (of 22 475 people) occurred during the 26-year study period. A linear exposure-response corresponding to a 3-7% decrease in AMI hospitalisations was observed for an inter-quartile range (IQR) increase in the 2-day cumulative average of temperature during the entire year (11 °C) or the warm period (6 °C), with and without adjustment for PM10, NO2, NOx or O3. No heat waves occurred during the warm period. No evidence of an association in the cold period was observed. No susceptible groups, based on age or sex, were identified either. Conclusions: An inverse association between temperature and AMI hospitalisations (entire year and warm period) was found in Gothenburg, and this is in accordance with the majority of the few other studies that investigated this subtype of CVD. Tentative mechanisms include physiological (less vasoconstriction) and psychosocial (general well-being) factors associated with a warmer climate (without heat waves).