Lower temperature, cold spells tied to increased risk of hospitalization for MI

Short-term exposure to lower air temperature and cold spells may elevate the risk of hospitalization due to myocardial infarction (MI) at a lag of 2 to 6 days, suggests a study in Sweden.

A total of 120,380 MI patients admitted to hospitals in Sweden during the cold season (October to March) from 2005 to 2019 were included in this population-based nationwide study.

Machine learning was used to estimate the daily mean air temperature. The percentiles of daily temperatures experienced by individuals in the same municipality were used as individual exposure indicators to explain the potential geographic adaptation.

A cold spell was characterized by periods of at least 2 consecutive days with a daily mean temperature below the 10th percentile of the temperature distribution for each municipality.

The authors used a time-stratified case-crossover design incorporating conditional logistic regression models with distributed lag nonlinear models using lag 0 to 1 (immediate) and 2 to 6 days (delayed) to assess short-term effects of lower air temperature and cold spells on total MI, non‒ST-segment elevation MI (NSTEMI), and ST-segment elevation MI (STEMI).

A decrease of 1-U in percentile temperature at a lag of 2 to 6 days resulted in a significantly higher likelihood of total MI (odds ratio [OR], 1.099, 95 percent confidence interval [CI], 1.057‒1.142), NSTEMI (OR, 1.110, 95 percent CI, 1.060‒1.164), and STEMI (OR, 1.076, 95 percent CI, 1.004‒1.153).

Cold spells at a lag of 2 to 6 days also contributed to an elevated risk of total MI (OR, 1.077, 95 percent CI, 1.037‒1.120), NSTEMI (OR, 1.069, 95 percent CI, 1.020‒1.119), and STEMI (OR, 1.095, 95 percent CI, 1.023‒1.172). On the other hand, lower air temperature and cold spells at a lag of 0 to 1 day resulted in a reduced risk for MI.