Global, local actions can tackle ‘unprecedented pace’ of climate change, heart disease
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Data support the concept that a changing climate driven, in part, by human behaviors has had a growing impact on public health, with increasingly extreme weather events disproportionately affecting people at highest risk for CVD.
Wildfires and associated air pollution are increasing, yet air pollution is an often-overlooked risk factor for CVD. According to the Global Burden of Disease study, pollution was responsible for 9 million deaths worldwide in 2019, 61.9% of which were due to CVD, including ischemic heart disease (31.7%) and stroke (27.7%). In a recent article on pollution and the heart published in The New England Journal of Medicine, researchers noted the numbers likely undercount the full contribution of pollution to the global burden of CVD, as they are based on only a subset of environmental risk factors.
“Climate change is at the center of reducing CVD burden, because the same solutions that are good for your heart are also good for the planet,” Sanjay Rajagopalan, MD, chief of the division of cardiovascular medicine and chief academic and scientific officer of University Hospitals Harrington Heart & Vascular Institute and Herman K. Hellerstein, MD, Chair in Cardiovascular Research at Case Western Reserve University, told Cardiology Today. “These include increasing physical activity, increasing active modes of transport, reducing red meat and high calorie consumption and mitigating stress. If you look at the overall picture of what is required for mitigating climate change, it is all the same things that make you live longer and reduce heart disease.”
In the annual American Society for Preventive Cardiology President’s Message published in August in the American Journal of Preventive Cardiology,Martha Gulati, MD, MS, FACC, FAHA, FASPC, FESC, wrote that the “continued temperature rise, along with heat waves that are occurring in greater frequency, intensity and duration, are resulting in heat-related premature mortality or morbidity, and quite frequently present as ischemic heart disease or stroke.”
“We are all watching or experiencing extremes of weather,” Gulati, also professor of medicine at the Smidt Heart Institute at Cedars-Sinai, director of CVD prevention and associate director of the Barbra Streisand Women’s Heart Center, told Cardiology Today. “You cannot watch the news without hearing about tornadoes, extreme heat, floods, changed summers and winters. At those extremes of weather is when we also see increased CV events. As preventive cardiologists, we have to talk about the environment and its effect on our patients. What can we do? We cannot tell a patient to move from their home; however, we can be advocates for a better environment in the communities where we live and work.”
In a position paper published in November in Annals of Internal Medicine,Ryan Crowley, BSJ, senior associate for health policy at the American College of Physicians, and colleagues wrote that the organization “recognizes that human and planetary health are interconnected, and that climate change is a global human and environmental health crisis.”
Environmental quality can also “contribute to common diseases” like asthma, heart disease, stroke and cancer, the authors wrote.
Changing urban footprint
The proportion of the world’s population living in urban areas rose from 34% in 1960 to 56% in 2019, according to 2021 data from the World Bank. The U.N. Population Division projects that number will grow to 68%, or 6.6 billion people, by 2050, with most of the growth taking place in low- and middle-income countries.
Urban environments are a central issue related to climate change — and, by extension, CVD risk, Rajagopalan said.
“The average North American city is designed to induce chronic cardiovascular disease,” Rajagopalan said. “Urban societies and cities contribute more than 75% of CO2 emissions, partly because of the way we live our lives.”
Urban centers tend to be closer to highways and industrial hubs, all of which increase pollution exposure and drive CV risk, Gulati said.
“Even if you try hard to control traditional risk factors, we cannot choose entirely where we live,” Gulati said. “That is challenging when taking care of patients. There is so much about a person’s ZIP code that teaches us what they deal with. If you live in an urban area, how close do you live to the highway? Do you have factories in your backyard vs. other neighborhoods? Do you have access to green spaces? We cannot ignore problems in our environment much longer.”
In addition to increased pollution, urbanization has also brought several key societal behavior shifts, Rajagopalan said.
“We have shifted to a society where we drive to work and sit in a chair, all day. We eat extremely ‘energy-dense’ foods,” Rajagopalan said. “Things we normally ascribe to ‘lifestyle’ are actually indirectly related to the lives we lead in urban societies. Solving this problem will take a fundamental shift in how we design cities, how we consume energy, how we commute. It is a massive shift in the way we think.”
Pollution and CVD
Air pollution is a complex mixture of airborne pollutants that generates CVD through several pathways, according to Michael B. Hadley, MD, MPH, cardiology fellow and incoming assistant professor of medicine (cardiology) at the Icahn School of Medicine at Mount Sinai. Components include particulate matter (PM) and gaseous pollutants such as ozone, nitrogen dioxide, volatile organic compounds, carbon monoxide and sulfur dioxide. PM is usually classified into three size groups: coarse particles (PM10); fine particles (PM2.5); and ultrafine particles (< 0.1 µm). PM2.5 originates from combustible and noncombustible sources, including industrial sources, tailpipe emissions, wildfires, and agricultural, biomass and coal burning. The American Heart Association and the European Society of Cardiology both recognize PM2.5 as a CV risk factor.
“During the last 10 years, there has been a growing evidence base that fine particulate matter and air pollution is an independent risk factor for CV mortality and other CV events, like HF, stroke and MI,” Hadley told Cardiology Today. “That fine particulate matter can come from a variety of sources; the one we think about the most is the burning of fossil fuels. In the setting of climate change, a growing source is wildfire air pollution.”
Hadley and colleagues recently developed a special survival model to estimate the independent associations between eight environmental exposures and all-cause and CV mortality in a cohort of more than 50,000 people living in rural Iran. The model, using satellite data to assess combined environmental exposures, showed ambient fine particulate matter air pollution, along with household fuel use and ventilation, drove risk for CV death independent of other factors. The data were published in PLOS ONE in June.
“You can talk about who is the most highly exposed and who is the most susceptible. Usually, the highest-risk populations are both,” Hadley said. “The most highly exposed could be someone living next to a major highway, exposed to traffic pollution. It could be someone on the edge of a national park exposed to wildfire. Someone living in New Delhi or Beijing could be exposed to industrial pollution. Geography matters a lot. In terms of who is the most susceptible, the key groups are anyone with preexisting CVD.”
Extreme temperatures and the heart
Data suggest heat exposure contributes to the exacerbation of CVD, and the intensity and duration of extreme heat waves in the U.S. and globally have steadily increased, in part due to increased air pollution. In a study published in December in Circulation that used a multinational data set across climate zones from 1979 to 2019, researchers found that at extreme temperature percentiles, heat (99th percentile) and cold (1st percentile) were associated with higher risk for dying from any CV cause, ischemic heart disease, stroke and HF compared with the minimum mortality temperature, which is the temperature associated with least mortality. HF was associated with the highest excess deaths proportion from extreme hot and cold days with 2.6 (95% CI, 2.4-2.8) and 12.8 (95% CI, 12.2-13.1) for every 1,000 HF deaths, respectively.
“The topic of climate change and CV health received little attention from cardiologists despite the great advancements in CV prevention research and the abundance of data,” Barrak Alahmad, MD, PhD, MPH, research fellow at Harvard T.H. Chan School of Public Health and faculty member at Kuwait University College of Public Health, told Cardiology Today. “Professional cardiology societies need to be on top of environmental exposures, such as extreme temperatures. In this rapidly changing climate and an unprecedented pace of warming, it is not the time to be asleep at the driving wheel.”
“We know that the CV system plays a central role in regulation of heat in the body,” Sameed Khatana, MD, MPH, assistant professor of medicine at the University of Pennsylvania Perelman School of Medicine and staff cardiologist at Philadelphia VA Medical Center, told Cardiology Today. “When a person is exposed to extreme heat, there is an increased risk for adverse CV events because the CV system is working harder to regulate heat. People with preexisting heart disease are at very high risk because their CV system may not be able to keep up with the excess demands placed on the body due to heat exposure.”
Khatana and colleagues recently analyzed daily maximum heat index levels for 3,108 counties in the contiguous U.S. during summer months (May-September) from 1979 to 2017, using data from the National Environmental Public Health Tracking Network. Researchers also assessed monthly CV mortality rates for adults using data from the National Center for Health Statistics. For each county, an extreme heat day was defined as a maximum heat index of at least 90°F and at least the 99th percentile of the maximum heat index in a baseline period (1979-2007) for that day.
From 2008 to 2017, each additional extreme heat day during summertime months was associated with a 0.13% increase in monthly adult CV mortality rates. This association was significant for men but not women.
Among race/ethnicity subgroups, this association was significant for Black adults, but not for white or Hispanic adults.
“There are differences in the prevalence of CV risk factors and CVD between different populations, but there are also differences in where people live,” Khatana said. “Data show neighborhoods with a higher proportion of minorities are more prone to the effects of extreme heat. Reasons include lower tree cover and differences in insulation materials for buildings.’”
Khatana said cardiologists must be proactive in addressing steps patients can take during periods of extreme heat.
“There is an association between extreme heat and CV deaths, and cardiologists need to realize their patients are at the highest risk for this outcome,” Khatana said. “We must inform patients about this risk when an extreme heat event is projected, making sure patients know to get to cool environments. If people indicate they do not have access to air conditioning, work to connect people to resources, like cooling centers.”
‘We need to be the voice for change’
Physicians, nurses, medical societies and public health organizations are uniquely positioned to urge governments on behalf of their patients to end pollution and prevent disease, Rajagopalan said.
“As physicians, we are so used to putting out fires that we do not think about larger, existential issues like climate change,” Rajagopalan said. “We in the health care field have to be in the forefront of this conversation, transforming the environments that we work in and looking very closely at opportunities to reduce our emission footprint, both in the health system and as individuals who are part of the health ecosystem.”
Such opportunities can range from participating in big-picture advocacy efforts on Capitol Hill to assessing the products used in the hospital cafeteria or the operating room, Gulati said.
“On a local level, start with your own hospital or institution,” Gulati said. “Serve on the purchasing committees. Talk with leadership about why the environment should matter to the hospital system. We need to be the voice of change. If physicians do not speak up, administrators may not be aware of all the waste that we see with some of the products we use. Ask what products can be safely reused? What might be compostable?”
Some institutions are taking steps to adopt more sustainable practices. In 2020, Kaiser Permanente announced it achieved carbon-neutral status, improving energy efficiency by 8% since 2013 and decreasing water use intensity by 15.3%. The health system also adopted use of low-polluting anesthesia gases; about 3% of Kaiser greenhouse gas emissions come from gases used during medical procedures.
Clinicians should also take advantage of opportunities to have conversations about sustainability with patients, Hadley said.
“People become doctors because they want to help patients reduce disease burden,” Hadley said. “If that is truly our mission, we need to think more broadly about what the determinants of disease are. It is not just the individual anymore. It is the individual plus the environment. We need to take responsibility for helping people navigate those environments and live healthy lives.
“Climate change is the greatest threat to public health of this century,” Hadley said. “That is a statement by the United Nations. CVD is still the No. 1 killer globally. Working at the intersection of those problems — CVD and climate change — is a monumental task and an important one, and something I hope cardiologists can get excited about.”
- References:
- Alahmad B, et al. Circulation. 2022;doi:10.1161/CIRCULATIONAHA.122.061832.
- Crowley R, et al. Ann Intern Med. 2022;doi:10.7326/M22-1864.
- Kaiser Permanente. The road to carbon neutral. about.kaiserpermanente.org/community-health/improving-community-conditions/environmental-stewardship/the-road-to-carbon-neutral#. Accessed Dec. 5, 2022.
- Ganatra S, et al. Ann Intern Med. 2022;doi:10.7326/M22-1241.
- Gulati M. Am J Prev Cardiol. 2022;doi:10.1016/j.ajpc.2022.100375.
- Hadley MB, et al. Circulation. 2018;doi:10.1161/CIRCULATIONAHA.117.030377.
- Iyer Y, et al. Eur Heart J. 2022;doi:10.1093/eurheartj/ehac110.
- Rajagopalan S, et al. N Engl J Med. 2021;doi:10.1056/NEJMra2030281.
- For more information:
- Barrak Alahmad, MD, PhD, MPH, can be reached at balahmad@hsph.harvard.edu; Twitter: @barrak1.
- Martha Gulati, MD, MS, FACC, FAHA, FASPC, FESC, can be reached at martha.gulati@gmail.com; Twitter: @drmarthagulati.
- Michael B. Hadley, MD, MPH, can be reached at michael.hadley@mountsinai.org; Twitter: @michaelhadleymd.
- Sameed Khatana, MD, MPH, can be reached at sameed.khatana@pennmedicine.upenn.edu; Twitter: @sameedkhatana.
- Sanjay Rajagopalan, MD, FACC, FAHA, can be reached at sanjay.rajagopalan@uhhospitals.org.
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