When weather warnings go out, heat usually steals the spotlight. We hear about heat waves, dehydration, and how high temperatures can strain the heart.
But a massive new U.S. analysis suggests we’ve been missing a quieter, more consistent threat: cold weather.
Researchers found that colder-than-optimal temperatures are linked to far more cardiovascular deaths in the United States than warmer-than-optimal temperatures.
It is not just during rare blizzards or polar vortex events – the study suggests that even “routine” cold exposure plays a big role in heart attacks, strokes, and coronary artery disease.
What the researchers looked at
This study is described as the most comprehensive U.S.-wide analysis of temperature-related cardiovascular death trends to date.
Previous research has connected extreme temperatures to higher heart risk, but many studies have focused on other countries or smaller slices of the United States.
Here, the researchers analyzed more than 14 million cardiovascular deaths among people over age 25 across 819 U.S. counties, covering roughly 80 percent of the U.S. population from 2000 to 2020.
They linked mortality records with local temperature data. Then they used statistical models to estimate how far daily temperatures strayed from an “optimal” point and how that deviation increased the risk of death.
The key step was quantifying how many cardiovascular deaths could be attributed to cold versus heat.
Cold accounts for more heart deaths
The analysis identified 74°F as the “optimal” temperature – the point where cardiovascular mortality was lowest. Then the risk rose when temperatures moved away from that point, but not evenly.
Temperatures below 74°F were associated with about 40,000 cardiovascular deaths per year during the study period (about 6.3 percent of cardiovascular deaths). Temperatures above 74°F were associated with about 2,000 deaths per year (about 0.33 percent).
Over the full two decades, that adds up to roughly 800,000 deaths linked to colder temperatures. In comparison, about 40,000 deaths were linked to warmer temperatures.
Another way the study frames it is simple and memorable: about one in 16 cardiovascular deaths were linked to colder weather, compared with about one in 300 linked to heat.
That doesn’t mean heat is harmless. But it does suggest that, in the U.S., cold is the bigger and more consistent cardiovascular risk at the population level.
Aren’t there just more cold days?
One obvious pushback is that many parts of the U.S. spend more time below 74°F than above it. The researchers note that about 80 percent of observations in their dataset occurred at temperatures below 74°F.
They used statistical techniques to adjust for that imbalance, and even with those adjustments, heart-related mortality was still more common on colder days.
So this isn’t just a mathematical artifact of “more cold days.” Cold itself appears to be associated with meaningful cardiovascular risk.
Why cold is hard on the heart
The article doesn’t dive deeply into mechanisms, but clinically, the link makes sense. Cold exposure can raise blood pressure and heart workload, and it can trigger blood vessel constriction.
People are also more likely to do sudden intense exertion in cold weather (snow shoveling is the classic example), which can be a perfect storm for someone with underlying heart disease.
And unlike heat waves, cold risk can be sneaky because it feels “normal.” Many people don’t treat a chilly day as a health hazard.
“This may be surprising to many, but most temperature-related cardiovascular deaths are associated with cold, not heat,” said lead author Dr. Pedro Rafael Vieira de Olivera Salerno, an internal medicine resident of the Icahn School of Medicine of Mount Sinai.
“While heat waves are a major focus for health issues, colder temperatures are associated with far more heart-related deaths over time.”
Clinicians have long observed seasonal patterns in cardiovascular events. New findings now quantify how much cold exposure contributes at the population level. Even routine cold conditions – especially for vulnerable patients – can increase cardiovascular risk.
What this means for clinicians
The study’s message to clinicians is simple: treat cold exposure like a real cardiovascular risk factor, not an afterthought.
Risk rises during colder months, especially for older adults and people with preexisting cardiovascular disease.
The authors suggest cold-season risk should be incorporated into routine counseling and prevention strategies, not just reserved for extreme weather alerts.
What this means for heart patients
If you have heart disease – or you’re older, or you’ve had a heart attack or stroke – winter is not just uncomfortable. It can be risky.
The practical advice in the article is the kind you’d expect, but it matters because people often ignore it.
Stay warm and avoid getting chilled for long periods. Be cautious with sudden exertion in the cold (snow shoveling is a real trigger for some). Take medications consistently. In some cases, doctors may need to adjust medications during extreme cold.
Again, the important idea is that the risk isn’t limited to rare deep-freeze events. “Normal” cold days can still add strain.
The bigger gap this study exposes
Public health messaging has done a decent job raising awareness about heat. But this analysis suggests we’ve left a big prevention opportunity on the table by not treating cold exposure with the same seriousness.
Cold doesn’t feel like a dramatic crisis the way a heat wave does. But when you zoom out across an entire country and two decades of data, it appears to be the bigger cardiovascular threat.
The study is published in the American Journal of Preventive Cardiology.
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