Snow Shoveling Heart Attack Risk: Why a Storm Sends People to the Hospital

A 20 centimeter snowfall in Quebec, about eight inches, was followed the next day by a measurable jump in men admitted to hospital with a heart attack. Snow shoveling heart attack risk comes down to three stresses landing on the heart at once. Cold air constricts blood vessels and reduces the heart’s own oxygen supply. Sustained static work by the arms and shoulders holds a load without the rhythmic leg movement that normally helps blood return. And lifting a full shovel brings on breath holding. In that Quebec analysis, drawn from 128,073 admissions and 68,155 deaths across 33 winters, 20 cm of snow compared with none was associated with a 16% higher likelihood of a man being admitted for a heart attack the following day and a 34% higher likelihood of dying from one, with no measurable increase among women (CMAJ, 2017). Measured during actual shoveling, healthy untrained men reached 97% of maximum heart rate within 10 minutes and a systolic blood pressure of 198 mmHg, slightly higher than the same men hit on a maximal treadmill test (JAMA, 1995).

Portland averages 68.7 inches of snow a year. Concord, New Hampshire, averages 67.7. Caribou nearly doubles both. That is a lot of driveway, cleared by the oldest population in the country.

Why snow shoveling heart attack risk is different from other hard work

Start with the cold. A review of cold exposure and cardiovascular disease notes that cold reduces myocardial oxygen supply in people with coronary artery disease, which may lead to ischemia, and that exercise in the cold “often augments cardiac workload in persons with CAD more than when performed in thermoneutral conditions.” No source puts a number on how much cold narrows a coronary artery, so distrust any article that gives you one.

Then the shape of the work. Shoveling is arms and shoulders holding a load, closer to weightlifting than to walking. Intra-arterial recording during heavy resistance exercise found a single-arm curl to failure produced mean peak pressures of 255/190 mmHg, part of that rise traced to a Valsalva maneuver, the breath holding people do without noticing when they strain. Pressures go extreme, the authors concluded, even with a small working muscle mass.

One study measured the real thing. Ten healthy untrained men, average age 32, cleared 15 meter tracts of heavy wet snow about 10 cm deep at 2 degrees C. Heart rate hit 154 beats per minute at two minutes and 173 at ten, or 86% and 97% of maximum. Systolic pressure averaged 198 mmHg, above what those same men produced on a maximal treadmill test. Young men. In their thirties. Healthy.

What the storm data shows, and where it disagrees

The Quebec study is the largest of its kind, a case-crossover design covering November through April, 1981 to 2014. Against no snowfall, 20 cm carried odds of 1.16 (95% CI 1.11 to 1.21) for a heart attack admission the next day among men and 1.34 (1.26 to 1.42) for a heart attack death. Among women, 1.01 and 1.04, both intervals crossing 1.

British Columbia found the same shape on a smaller scale. Days with 5 cm or more of snow carried 34% higher odds of death from a heart attack, though the interval ran from 0% to 80%, so it barely clears significance. And risk was significantly higher when the temperature was warmer. Warmer snow is heavier snow.

Then a study that found close to nothing. Calgary researchers compared 61 snow days with 575 non-snow days and saw heart attack incidence only slightly higher (incidence density ratio 1.08, 95% CI 0.82 to 3.10). Nothing reached significance, and the authors wrote that their findings “suggest only minor effects, if any.” A body of evidence with a clean null in it is worth more than one without.

The Maine and New Hampshire numbers

In NOAA’s 1991 to 2020 normals, 49.8 of Portland’s inches and 48.3 of Concord’s arrive in December through February, and Caribou takes 75.5. Snow sits on the ground 74.2 days a year in Portland, 91.7 in Concord and 135.7 in Caribou.

Maine has the highest share of residents aged 65 and older of any state, 23.5% against a national 18.0%, plus roughly 332,700 men aged 45 and older, about one in four Mainers. New Hampshire ranks seventh at 21.5%. Heart disease mortality tracks the male pattern in the Quebec data: the CDC’s 2021 to 2023 age-adjusted rate for adults 35 and older runs 403.9 per 100,000 for Maine men against 250.1 for Maine women, a gap of 62%. Heart disease is the leading cause of death in Maine, the second in New Hampshire.

Cardiac deaths in both states already run higher in winter than in summer, before any storm enters the picture. In CDC weekly counts for 2014 to 2019, Maine averaged 59.0 deaths from diseases of the heart per week in December through February against 51.5 in June through August, about 15% higher; New Hampshire, 54.3 against 45.8. That gap is context, not attribution. Influenza, cold exposure and indoor air all feed winter cardiac mortality, and no study apportions the excess.

Who actually ends up in the emergency department

Emergency department surveillance gives the broadest count: an estimated 195,100 people treated for snow shovel related incidents between 1990 and 2006, about 11,500 a year. Two thirds male; adults 55 and older, 21.8% of cases. Cardiac visits accounted for 6.7% of the total and for all 1,647 deaths in the study, spread across 17 winters. Annual death tolls get quoted every December, usually around a hundred. None traces back to a source that publishes one, and this sort of estimate is too unstable for the literature to convert into a yearly rate.

A Kingston, Ontario, chart review adds texture. Of 500 acute coronary syndrome patients seen across two winters, 35 events, 7%, followed snow shoveling. Those patients were 4.8 times more likely to be male and 3.6 times more likely to have a family history of premature cardiovascular disease. What did not separate the groups is the interesting part: no significant difference in diabetes, hypertension, high cholesterol or sleep apnea.

A CDC review of charts at 12 Suffolk County hospitals after the January 1996 New York blizzard complicates that. Blizzard conditions brought more visits for heart attack and angina, primarily shoveling-related. Most of those patients did not report pre-existing heart disease, and a quarter of the heart attack and angina visits by women were reportedly shoveling-related. Warnings, the authors wrote, “may be less effective at decreasing shoveling-induced myocardial infarction if they are directed primarily at men and at people with heart disease.” Lower risk on average is not no risk.

The machine in the garage does not settle it

Two pieces of standard winter advice do not survive the measurements. The first is that a snow blower removes the problem. In 10 men with asymptomatic coronary artery disease, oxygen uptake and heart rate while snow blowing did not differ significantly from shoveling; in 10 older and 6 younger men without coronary disease, both dropped significantly. The machine helped the men who needed help least. How cold changes the cost of exertion comes up again in our notes on exercising outdoors through a northern New England winter.

The second is that pushing snow is easier on the heart than lifting it. When nine men cleared snow 400 to 600 mm deep, oxygen consumption ran 2.1 L/min with a shovel (63% of VO2max) and 2.6 L/min with a snow pusher (75%), a significant difference in the direction nobody expects. The authors called manual snow clearing in heavy-snowfall conditions strenuous work “not suitable for persons with cardiac risk factors.”

What the guidance says, and what Maine’s does not

The National Institute on Aging tells older adults to “avoid shoveling snow yourself when possible,” noting that alongside the risk of falling there is a risk of heart attack while shoveling. Falling is the other hazard on that walkway, covered in our piece on winter falls and Maine’s older population. The National Weather Service says to avoid overexertion such as shoveling heavy snow if you are not in good health, because “the strain from the cold and the hard labor may cause a heart attack.”

Maine’s own guidance is quieter. The Maine CDC’s cold-related illness page warns that during “Maine’s long winters” residents face hypothermia and frostbite, and names people with chronic cardiovascular or lung conditions among those at increased risk. The word “shovel” does not appear on it. Nor is there any published Maine or New Hampshire count of shoveling-related cardiac events. The storm research comes from Quebec, British Columbia, Calgary, Kingston and Long Island. The snow is ours.

None of this converts into a rule for a particular driveway. These studies measure populations, and the federal guidance above is quoted as issued, not a plan for anyone’s February. Whether snow clearing is reasonable work for a specific person is a conversation for a clinician who knows the case. Readers tracking how their body handles hard efforts may find our explainer on what heart rate variability actually measures useful for framing it, with a caveat: a number on a wrist is not a diagnosis. The narrower point is harder to shrug off. Snow removal is heavy exertion in cold, done by a population older than almost any other in the country, and the next storm is already on the calendar.

Sources

• Auger N, Potter BJ, Smargiassi A, et al. Association between quantity and duration of snowfall and risk of myocardial infarction. CMAJ. 2017;189(6):E235-E242. https://pmc.ncbi.nlm.nih.gov/articles/PMC5305403/
• Franklin BA, Hogan P, Bonzheim K, et al. Cardiac demands of heavy snow shoveling. JAMA. 1995;273(11):880-882. https://pubmed.ncbi.nlm.nih.gov/7869560/
• Gan WQ, Sasakawa Y, McLean KE, et al. Snowfall, Temperature, and the Risk of Death From Myocardial Infarction: A Case-Crossover Study. American Journal of Epidemiology. 2020;189(8):832-840. https://pubmed.ncbi.nlm.nih.gov/32128571/
• Southern DA, Knudtson ML, Ghali WA. Myocardial infarction on snow days: incidence, procedure, use and outcomes. Canadian Journal of Cardiology. 2006;22(1):59-61. https://pmc.ncbi.nlm.nih.gov/articles/PMC2538986/
• Watson DS, Shields BJ, Smith GA. Snow shovel-related injuries and medical emergencies treated in US EDs, 1990 to 2006. American Journal of Emergency Medicine. 2011;29(1):11-17. https://pubmed.ncbi.nlm.nih.gov/20825768/
• Nichols RB, McIntyre WF, Chan S, et al. Snow-shoveling and the risk of acute coronary syndromes. Clinical Research in Cardiology. 2012;101(1):11-15. https://pubmed.ncbi.nlm.nih.gov/21904937/
• Blindauer KM, Rubin C, Morse DL, McGeehin M. The 1996 New York blizzard: impact on noninjury emergency visits. American Journal of Emergency Medicine. 1999;17(1):23-27. https://pubmed.ncbi.nlm.nih.gov/9928692/
• Sheldahl LM, Wilke NA, Dougherty SM, Tristani FE. Snow blowing and shoveling in normal and asymptomatic coronary artery diseased men. International Journal of Cardiology. 1994;43(3):233-238. https://pubmed.ncbi.nlm.nih.gov/7514155/
• Smolander J, Louhevaara V, Ahonen E, et al. Energy expenditure and clearing snow: a comparison of shovel and snow pusher. Ergonomics. 1995;38(4):749-753. https://pubmed.ncbi.nlm.nih.gov/7729401/
• MacDougall JD, Tuxen D, Sale DG, Moroz JR, Sutton JR. Arterial blood pressure response to heavy resistance exercise. Journal of Applied Physiology. 1985;58(3):785-790. https://pubmed.ncbi.nlm.nih.gov/3980383/
• Ikaheimo TM. Cardiovascular diseases, cold exposure and exercise. Temperature (Austin). 2018;5(2):123-146. https://pmc.ncbi.nlm.nih.gov/articles/PMC6204981/
• National Institute on Aging, National Institutes of Health. Cold Weather Safety for Older Adults. https://www.nia.nih.gov/health/safety/cold-weather-safety-older-adults
• NOAA National Weather Service. Winter Safety: During a Winter Storm. https://www.weather.gov/safety/winter-during
• NOAA National Centers for Environmental Information. 1991-2020 US Climate Normals, annual and seasonal access files (Portland, Concord and Caribou stations). https://www.ncei.noaa.gov/access/us-climate-normals/
• Maine CDC, Maine Department of Health and Human Services. Cold-related Illness. https://www.maine.gov/dhhs/mecdc/healthy-living/health-and-safety/climate-and-health/cold-related-illness
• CDC Division for Heart Disease and Stroke Prevention. Heart Disease Mortality Data Among US Adults (35+) by State/Territory and County, 2021-2023. https://data.cdc.gov/d/th8y-thx5
• National Center for Health Statistics, Division of Vital Statistics. Weekly Counts of Deaths by State and Select Causes, 2014-2019. https://data.cdc.gov/d/3yf8-kanr
• US Census Bureau. Vintage 2024 State Characteristics Population Estimates, civilian population by single year of age and sex. https://www.census.gov/data/tables/time-series/demo/popest/2020s-state-detail.html

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any health decisions.