Ambient temperature and hospital admissions for non-ST segment elevation myocardial infarction in the tropics

Background: Myocardial infarction is an important cause of cardiovascular mortality and can be precipitated by cli-matic factors. The temperature dependence of myocardial infarction risk has been well examined in temperate set-tings. Fewer studies have investigated this in the tropics where thermal amplitudes are narrower. This study investigated how ambient temperature influenced the risk of non-ST segment elevation myocardial infarction (NSTEMI), an increasingly common type of myocardial infarction, in the tropical city-state of Singapore.Methods: All nationally reported NSTEMI cases from 2009 to 2018 were included and assessed for its short-term asso-ciation with ambient temperature using conditional Poisson regression models that comprised a three-way interaction term with year, month and day of the week and adjusted for relative humidity. The Distributed Lag Non-Linear Model-ling (DLNM) was used to account for the immediate and lagged effects of environmental exposures. Stratified analysis by sex and age groups was undertaken to assess potential effect modification.Results: There were 60,643 reports of NSTEMI. Temperature decline (cool effect) was associated with a delayed cumu-lative, non-linear increase in NSTEMI risk over 10 days post exposure [Relative Risk (RRlag0-10, 10th percentile: 1.12, 95% CI: 1.02-1.24)]. Those aged 65 years and above were potentially more susceptible (RR lag0-10, 10thpercentile:1.19, 95 % CI: 1.06-1.33) to the cool effect compared to those below that age (RRlag0-10, 10th percentile: 1.00, 95 % CI: 0.85-1.18) (p-value for difference = 0.087).Conclusion: Short-term temperature fluctuations were independently associated with NSTEMI incidence in the tropics, with age as a potential effect modifier of this association. An increase in the frequency of climate change driven temperature events may trigger more instances of NSTEMI in tropical cosmopolitan cities.

Automated summary

The study investigated the association between ambient temperature and non-ST segment elevation myocardial infarction (NSTEMI) in the tropical city-state of Singapore. Results showed that temperature decline was associated with a delayed cumulative increase in NSTEMI risk, with older age groups potentially more susceptible.