Q&A: Extreme temperature within ‘heat dome’ poses harm to vulnerable populations
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Key takeaways:
- The “heat dome” over the Northeast and Midwest may cause increased CV risk in vulnerable populations.
- An NYU Langone cardiologist provided insight on how best to advise patients during times of extreme heat.
A “heat dome” has descended on the U.S. Northeast and Midwest, bringing with it daily highs in the triple digits and potentially hazardous living conditions, especially for underserved communities and those with chronic health conditions.
Heat domes occur when a region of high pressure traps heat over a particular area. They are typically caused when the jet stream moves northward, moves slower and sinks, lowering humidity and allowing the sun to create hotter conditions on the ground, according to a report issued by the National Oceanic and Atmospheric Administration.
With excessive heat watch alerts from the National Weather Service in effect through June 23 in some areas, the Weather Channel reports expected heat indexes in the region to exceed 100°F.
Such temperatures may increase risk for heart-related adverse events, especially in vulnerable populations, according to Jonathan Newman, MD, MPH, a cardiologist at the NYU Langone’s Center for the Prevention of Cardiovascular Disease.
Healio spoke with Newman about the impending heat dome, the excess CV risk posed by extreme temperatures and how clinicians can counsel their patients at risk for adverse events caused by the hot weather.
Healio: Annually, what is the burden of CV hospitalizations and deaths attributable to excess heat exposure?
Newman: The best data we have are from things like the Global Burden of Disease studies and international assessments of different health outcomes over time. The most recent data are from 2019 to 2020. That has estimated that heat itself has led to approximately 100,000 CV deaths worldwide in 2019, alone. So it’s a substantive burden of mortality on an annualized basis worldwide.
Most of the data comes from developed or postindustrial countries like the United States, Western Europe and Australia. But the burden of these heat waves globally is felt disproportionately in lower- or middle-income countries, “the Global South,” from which we have more limited data.
Healio: Generally, by what mechanism does excess heat exposure increase CV risk?
Newman: The mechanisms of this are not fully understood. As with all environmental exposures, including heat and climate change in general, we’re not exposed to just one thing. It’s heat with high humidity, and it’s heat with poor air quality or high levels of ozone and other things that interact with heat.
For heat alone, what happens from a CV perspective is increased vasodilatation leading to increased sweating and dehydration. That in and of itself can lead to a mismatch between oxygen supply and demand and physiologic stress on the heart, leading to increased cardiac load, resulting in heart failure or myocardial infarction from myocardial work.
There is some evidence that increased heat leads to upregulation of inflammatory pathways leading to downstream effects on atherosclerotic plaque, leading to plaque rupture and MIs. But a lot of these pathways are not fully worked out.
Heat regulation is a complex physiologic stressor, the extremes of which — hypothermia and hyperthermia — can have adverse CV effects, broadly speaking.
Healio: Under what environmental conditions do you start to see excess CV risk?
Newman: It’s more a question of context. We’re interacting with the environment in a complex milieu. Let’s say it’s high temperature, high humidity, high levels of air pollution and low levels of green space availability or natural barriers and modifiers of heat exposure. That’s the situation with these “heat islands.” We’ve known for a long time that a lot of the adverse effects of environmental exposures, such as heat waves, are felt disproportionately on communities with fewer resources, that are disadvantaged from an environmental perspective based on a lot of complex factors that further exacerbate the effects of a heat wave.
Healio: Are there specific patient populations at especially high risk during these periods of excess heat exposure?
Newman: The older individuals in our population and the youngest, infants and babies, both of whom have changes in the way that their bodies cool and their abilities to regulate heat and sweat.
Pregnant women are more susceptible to heat-related illness due to the physiologic stress of the mother and the fetus and influences on their thermal regulatory systems.
Outdoor workers, construction workers, people working on the roadsides and people that can’t be indoors during the day because of their places of employment are vulnerable.
There are medications that are very common that may raise risk, and particularly for CVD. Diuretics, which are used to manage HF, kidney disease and high blood pressure, reduce your fluid balance from frequent urination and, obviously, can lead to dehydration, particularly during heat waves, and can make it harder for you to regulate temperature.
Other common medications for vulnerable populations with preexisting CVD include ACE inhibitors that are used to treat high BP, increase risk for fainting and can sometimes suppress your sense of thirst.
Beta-blockers, another common medication, can also increase the risk for fainting, make it harder to sweat and keep yourself cool.
Another vulnerable population are those living in lower-middle-income countries and communities that have higher heat exposure and limited access to care. Other vulnerable groups include disadvantaged populations in New York, redlined communities, communities with limited green space and Indigenous communities that may be less resilient to some of the heat-stress and environmental changes that we’re experiencing.
Healio: How should physicians counsel their at-risk patients leading up to this impending heat dome?
Newman: The first thing is, know the symptoms of heat exhaustion. If you’re heavy sweating, cold and clammy, nauseous, vomiting, have cramps, feel dizzy, fatigued or fainting, that’s reaching the level of medical emergency and you need to seek urgent care.
When you’re experiencing heat stroke, your skin may actually look different. You can look red, hot, dry; you can be confused. That’s another emergency circumstance where you need to seek care.
During the heat dome periods, avoid strenuous outdoor activity during the really hot hours of the day, if you can. Stay in an air-conditioned environment, if you have access to one. Visit a cooling center in urban environments in New York and New Jersey, including libraries.
If you’re going to be outside, seek shade, wear light loose-fitting clothing, wear a hat and drink a lot of water. Eight oz every 15 to 20 minutes. Staying hydrated is a key component of this.
In 2020, during a heat wave amid the COVID-19 pandemic, New York City distributed over 70,000 air conditioners to older adults in public housing and low-income older adults, to encourage people to stay inside to prevent both COVID-19 exposure in congregate settings and to remain cool. So there are ways that we can do this, by using individual approaches and leveraging resources and air conditioning systems.
Healio: Is there anything else you would like to add?
Newman: While we’ve certainly had hotter temperatures than what we’re going to experience in this heat dome, this is a significant heat wave because we’re at the extreme of temperature relative to what we would normally be experiencing in the month of June. That’s why we’re calling this a heat dome, because it’s not usually where we are at this time of year, and unfortunately may be something we continue to deal with.
For more information:
Jonathan Newman, MD, MPH, can be reached at NYU Langone Cardiac Rehab Associates, 240 E. 38th St., 16th Floor, New York, NY, 10016.
References:
- Extreme heat and severe weather plague parts of North America. https://www.nesdis.noaa.gov/news/extreme-heat-and-severe-weather-plague-parts-of-north-america. Published June 30, 2023. Accessed June 19, 2024.
- Lam L. Long-lived heat wave to break more temperature records In Midwest, East. https://weather.com/forecast/national/news/2024-06-13-record-heat-forecast-midwest-northeast. Published June 19, 2024. Accessed June 19, 2024.
- National Weather Service | Alerts. https://alerts.weather.gov/search. Accessed June 19, 2024.
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