Cold Weather Linked to Significantly Higher Cardiovascular Deaths Than Heat

New research indicates that months with lower temperatures are associated with significantly higher rates of death from heart attacks, strokes, and coronary artery disease compared to milder months. Hotter temperatures were also linked to increased cardiovascular deaths, though at a more modest rate.

Dr. Pedro Rafael Vieira De Oliveira Salerno, lead author, noted that the burden of excess deaths related to cold is substantial.

Previous studies have connected temperature extremes with higher cardiovascular mortality, but this new study offers a comprehensive analysis across a large segment of the U.S. population.

Understanding the Research

Researchers analyzed monthly temperatures and total cardiovascular deaths across 819 U.S. locations. This encompassed approximately 80% of the U.S. population over 25, with data collected from 2000-2020.

The study found that the lowest rate of cardiovascular death was observed at 23° C (about 74° F). Rates increased as temperatures deviated both above and below this optimal point.

The Lopsided Curve: Cold's Greater Impact

Cardiovascular death rates showed a lopsided u-shaped curve, with a steeper and larger increase on the colder side. Cold weather was estimated to cause about 40,000 excess cardiovascular deaths annually during the study period, totaling 800,000 deaths over two decades. This significant figure represents 6.3% of all cardiovascular deaths.

In contrast, hot weather accounted for approximately 2,000 excess deaths annually, totaling 40,000 deaths over two decades. This accounts for a much smaller fraction, at 0.33% of all cardiovascular deaths.

How Cold Impacts the Body

Exposure to cold weather initiates physiological changes such as inflammatory processes and blood vessel constriction, which collectively increase the risk of adverse cardiovascular events. Individuals who are older or have chronic conditions are more susceptible to these effects, making them particularly vulnerable during colder months.

Implications for Public Health and Climate Planning

Dr. Salerno stated that as rates of chronic conditions like diabetes, heart failure, and chronic kidney disease rise, the number of people vulnerable to extreme temperatures will also increase. He emphasized that communities should consider the dangers of extreme cold in climate change planning, advocating for both heat and cold-related mitigation measures.

These findings can assist public health planning and healthcare institutions in anticipating increased emergency medical service calls and in-hospital mortality during cold periods.

Looking Ahead: Limitations and Future Research

The study's limitations include its reliance on monthly rather than daily temperature data and the assessment of health outcomes at a population level rather than individually.

A follow-up study is planned to track associations between temperature and EMS activations related to cardiovascular events. The study was published online in the American Journal of Preventive Cardiology.