Tuesday, 13 December 2023

According to new research published yesterday in the American Heart Association’s flagship journal Circulation, extremely hot and cold temperatures increased the risk of death among people with cardiovascular diseases, such as ischemic heart disease (heart problems caused by narrowed heart arteries), stroke, heart failure and arrhythmia.

Researchers explored how extreme temperatures may affect heart diseases – the leading cause of death globally. They analyzed health data for more than 32 million cardiovascular deaths that occurred in 567 cities in 27 countries on 5 continents, including Cyprus, between 1979 and 2019. The global data came from the Multi-Country Multi-City (MCC) Collaborative Research Network, a consortium of epidemiologists, biostatisticians and climate scientists studying the health impacts of climate and related environmental stressors on death rates.

Climate change is associated with substantial swings in extreme hot and cold temperatures, so the researchers examined both in the current study. For this analysis, researchers compared cardiovascular deaths on the hottest and the coldest 2.5% of days for each city with cardiovascular deaths on the days that had optimal temperature (the temperature associated with the least rates of deaths) in the same city.

For every 1,000 cardiovascular deaths, the researchers found that:

  • Extreme hot days accounted for 2.2 additional deaths.
  • Extreme cold days accounted for 9.1 additional deaths.

Of the types of heart diseases, the greatest number of additional deaths was found for people with heart failure (2.6 additional deaths on extreme hot days and 12.8 on extreme cold days).

One of the authors of the study, Assistant Professor in Environmental Health at UNIC Medical School Souzana Achilleos said ‘Specifically for Cyprus, we examined 14 years of mortality data (2004-17) from all Republic of Cyprus government controlled areas. At extreme temperature percentiles, heat (99th percentile = 30.7 oC) and cold (1st percentile = 8.30 oC) were associated with higher risk of dying from any cardiovascular cause, ischemic heart disease, stroke, and heart failure as compared to the minimum mortality temperature (27.6 oC), which is the temperature associated with least mortality. Extreme cold had a higher effect on the risk of cardiovascular mortality, and it was also associated with higher risk of dying from arrhythmia. In addition, it was estimated that for every 1,000 all-cause cardiovascular deaths, 13.5 [95%CI: 10.55,15.8] excess deaths were attributed to extreme cold (2.5th percentile and below) and  4.26 [95%CI: 2.71,5.6] to extreme heat temperatures (97.5th percentile and above).’

Researchers suggest targeted warning systems and advice for vulnerable people may be needed to prevent cardiovascular deaths during temperature extremes.

This study contributes important information to the ongoing societal discussions regarding the relationship between climate and human health. More work is needed to better define these relationships in a world facing climate changes across the globe in the years ahead, especially as to how those environmental changes might impact the world’s leading cause of death and disability, heart disease.