Cold exposure triggers a series of well-documented physiological responses in the body, primarily aimed at conserving core body heat. While these are adaptive in healthy people for short periods, they place significant stress on the cardiovascular system, especially in vulnerable individuals (e.g., elderly, those with coronary artery disease, hypertension, heart failure, or prior heart attacks). This helps explain why cold weather is linked to far more excess heart-related deaths (~40,000 annually in the U.S.) than heat, per the 2026 ACC study and supporting research.

The 2026 U.S. study attributes the excess deaths primarily to these physiological stresses from non-optimal (mostly moderate) cold temperatures.

There is a new major 2026 study presented at the American College of Cardiology’s Annual Scientific Session (ACC.26) and published in the American Journal of Preventive Cardiology.

Researchers analyzed monthly temperature data linked to cardiovascular mortality (heart attacks, strokes, coronary artery disease, etc.) across 819 U.S. counties covering about 80% of the U.S. population aged 25 and older from 2000 to 2020. They examined nearly 14.2 million cardiovascular deaths during this period.

Key Results

• The optimal temperature for lowest cardiovascular death risk was around 74°F (23°C).
• Risk rose in a U-shaped pattern as temperatures moved away from this point, but the increase was far steeper and larger on the cold side.
• Cold temperatures (below ~74°F) were linked to approximately 40,000 excess cardiovascular deaths per year — about 6.3% of all CV deaths — totaling roughly 800,000 over the two decades.
• Hot temperatures (above 74°F) accounted for only about 2,000 excess deaths annually (0.33% of CV deaths), or ~40,000 over 20 years.
• This means roughly 1 in 16 cardiovascular deaths was attributable to cold, versus 1 in 300 to heat. acc.org

Most excess cold-related deaths were driven by moderate cold rather than extreme freezes, simply because moderate cold occurs far more frequently across the year.

Why Cold Harms the Heart More

Cold triggers several physiological stresses:

• Vasoconstriction — blood vessels narrow, spiking blood pressure and forcing the heart to work harder.
• Increased blood viscosity and clotting tendency.
• Higher rates of respiratory infections that can strain the cardiovascular system.
• Reduced physical activity and delayed care-seeking during colder months.

These effects disproportionately affect older adults, people with existing heart conditions, and those in homes with poor insulation or heating.

This study aligns with larger global temperature-mortality research (e.g., Lancet analyses) showing cold consistently causes far more temperature-related deaths overall than heat — often by a factor of 9–20 times depending on the region and outcome measured. In the U.S., cold’s impact on heart health alone dwarfs heat’s contribution.

Important notes:

• These are statistically attributed excess deaths from modeling daily/ monthly temperature deviations, not just deaths directly coded as “hypothermia” on certificates (which undercount indirect effects).
• As the climate has warmed modestly, cold-related deaths have likely declined somewhat in recent decades, though an aging population with more chronic illness could offset some gains.
• Heat waves can still cause sharp short-term spikes, but cold’s year-round prevalence makes its cumulative burden much larger.

The data underscore that winter heart protection strategies — staying warm, managing blood pressure, getting flu shots, and avoiding overexertion in cold — warrant as much public attention as heat warnings. This doesn’t downplay heat risks but highlights a larger, often under-discussed seasonal threat.

Cardiovascular disease mortality attributable to monthly non-optimal temperature in the United States: a county-level analysis the exact title of a 2026 short report published in the American Journal of Preventive Cardiology (available online March 24, 2026). It was presented at the American College of Cardiology (ACC.26) Scientific Session as part of the Young Investigators Award Competition.

Authors: Pedro Rafael Vieira de Oliveira Salerno, Ricardo J. Estrada-Mendizabal, Weichuan Dong, Avery Hum, Zhuo Chen, Colin Capenter, Mohamed Bassiony, Sanjay Rajagopalan, Sadeer Al-Kindi, Salil V Deo.

American Journal of Preventive Cardiology

DOI: 10.1016/j.ajpc.2026.101514

American Journal of Preventive Cardiology, 2026

Introduction

Non-optimal ambient temperatures are increasingly recognized as an important environmental determinant of cardiovascular disease (CVD) mortality, with a characteristic non-linear exposure–response relationship in which both cold and heat are associated with excess risk [1,2]. In fact, non-optimal temperatures were estimated to account for nearly 90,000 deaths annually in North America between 2010 and 2019, with the vast majority attributable to cold exposure [1]. Notably, cold-related mortality in the US has more than doubled between 1999 and 2022 [3]. In the setting of increasing climate variability, quantifying temperature-related cardiovascular mortality, beyond those directly attributed to thermal causes, at the population level is essential to better inform prevention strategies and public health preparedness. Yet nationally representative analyses focused specifically on cardiovascular mortality remain limited. Therefore, in this study, we evaluated the association between monthly mean ambient temperature and CVD mortality at the county level across the United States from 2000 to 2020.

This paper provides robust, granular U.S.-specific evidence reinforcing broader global Lancet findings that non-optimal temperatures (especially cold) contribute significantly to CVD mortality, with cold imposing the larger burden due to exposure patterns. It supports balanced public health messaging that includes winter heart protection alongside heat preparedness.