According to research, extreme weather, an increase in vector-borne illnesses, and poor air quality, which are linked to climate change, may push rates of heart disease even higher than they are today. Climate change is expected to take an enormous toll on human health and, like heart health, its effects span the globe. “Climate change is unlike other health pandemics in that it cannot be solved by a vaccine,” says Barrak Alahmad, MBChB, MPH, a physician and Mission Scholar at Kuwait University and PhD Student at T.H. Chan School of Public Health at Harvard University in Cambridge. RELATED: Heart Health Awareness Month

According to the Global Heat Health Information Network, during the first 16 years of the new millennium, the number of people exposed to heat waves increased by 125 million. In addition to heat waves that both last longer and are more frequent, average minimum temperatures are also rising, says Juli Trtanj, who is responsible for developing and implementing a health strategy at the National Oceanic and Atmospheric Administration (NOAA). Trtanj says hotter average temperatures will result in people, cities, and environments losing the opportunity to cool down at night. Hotter-than-usual temperatures can have serious implications on heart health. In fact, the World Health Organization (WHO) recognizes that temperature affects heart-related mortality more than any other cause of death. In one study, published in March 2017 in the Iranian Journal of Public Health, researchers looked at 11 years of heart-related deaths in Mashhad, Iran, where the average summer high temperature is 94 degrees F. They then combined that data with temperature forecasts for the next five decades to create a simulation of how much heart-related deaths would increase in the city as the number of extreme heat days continued to rise. They found that an increase of just 1.8 degrees F in average maximum temperatures in Mashhad would lead to a 4 percent increase in cardiovascular deaths. Another study, published in March 2020 in the journal Circulation, showed that hotter days elsewhere in the Middle East are already leading to more heart-related deaths. Researchers analyzed seven years worth of cardiovascular deaths in Kuwait, which, in 2016, experienced the highest temperature recorded on Earth in the last 76 years. The team compared these heart-related deaths with daily average temperatures and found that 3 times as many people died of a cardiovascular event during days with the hottest temperatures, which were 109 degrees F and hotter. Also, in an analysis published in March 2019 in the European Heart Journal, German researchers documented an increase in heat-related heart attacks in recent years, compared with data from the past three decades. “When the core body temperature increases, the body tries to cool itself by shifting the blood from the organs to under the skin, says Dr. Alahmad, who coauthored the Kuwait study. “This increases the demand on the heart to pump blood.” Heat also causes the body to become more easily dehydrated, which causes changes in blood pressure. But extreme temperature isn’t the only type of weather that puts strain on the heart. Russell Luepker, MD, a professor emeritus in the division of epidemiology and community health at the University of Minnesota in Minneapolis, says that the physical and emotional stress that extreme weather — including extreme heat or cold as well as natural disasters like hurricanes, wildfires, and floods — put on the cardiovascular system can turn an acute heart problem into a fatal one. “The body responds to these extremes. Your heart rate rises and your blood vessels constrict and all of that is hard on the heart,” says Dr. Luepker. Climate change both fuels more powerful storms as well as major droughts that set up wildfires to burn hotter and longer. The stress of natural disasters disproportionately impacts the poor and the elderly, putting these populations at a higher risk of being hospitalized for a cardiac event following a natural disaster. One study, published in December 2018 in the International Journal of Environmental Research and Public Health, documented a spike in hospitalizations for cardiac events in Louisiana during the month following Hurricane Katrina. The data revealed that the storm disproportionately affected older adults, black Americans, and low-income communities who had less access to resources. “These situations affect not only the sick and the elderly, but middle-aged people who think they are healthy,” says Luepker.

Air Pollution, Especially Particulate Matter, Gets Absorbed in Lungs and Blood Vessels

Today, more than one-half of all countries have polluted air that exceeds national air quality standards set by the Environmental Protection Agency (EPA), according to a study published in March 2020 in the Journal of the American Heart Association. Air pollutants both exasperate climate change and are worsened by the impact climate change has on weather, especially greenhouse gasses. Methane and carbon dioxide are likely the greenhouse gasses that most people have heard about. These types of gases form a barrier that allows heat from sunlight into Earth’s atmosphere, but keeps a lot of that heat from escaping. According to Trtanj, this trapped heat speeds up the rate in which chemicals in the air interact with one another, which in turn, increases the amount of pollution in the air. And air pollution has huge repercussions for heart health. According to a study published in November 2017, in Archives of Cardiovascular Diseases, cardiovascular diseases account for 60 to 80 percent of air pollution–related deaths worldwide. Air pollution comes in many forms, but one type, particulate matter (PM), is the air pollutant that research has most strongly tied to heart health. The EPA separates particulate matter into two categories: inhalable coarse particles and fine particles like those found in smog. While the coarse particles are more likely to get trapped in the nose or throat, fine PM makes its way into the inner workings of the body. “Fine particulate matter can penetrate deep into the lungs and blood vessels, deposit there, and cause problems,” says Aruni Bhatnagar, PhD, a professor of medicine and chief of the division of environmental medicine at the University of Louisville in Kentucky. The March 2020 study analyzed data from more than 23,000 patients who were diagnosed with heart failure within a span of 12 years. The researchers found that, over a five-year period, people who had previously experienced heart failure and who lived in places with the highest levels of fine PM, died nearly one year earlier than those who were the least exposed, even if those people lived in places that met national air quality standards. When a person breathes air that is laced with fine particles, the pollution changes blood flow to the heart, resulting in higher blood pressure. When blood pressure increases, the heart has to work harder to keep up with the pace. Dr. Bhatnagar says that changes in blood pressure also impact blood vessels, creating eddys where plaque begins to build up. “Then, if you have rapid blood pressure changes, such as those induced by exercise or manual labor, these plaques can break down, dislodge, and clog the arteries,” says Bhatnagar. “That’s why higher pollution is associated with more heart attacks.” Even short-term exposure can cause damage. A study published in October 2018 in the Journal of the American College of Cardiology estimated that exposure to fine PM increases a person’s risk for an acute cardiovascular event within just a few days.

Vector-Borne Disease

According to the United States Agency for International Development (USAID), almost 75 percent of all new, emerging, or reemerging diseases that have impacted humans since the turn of the century originated in animals. Although the coronavirus is the starkest example of this, for years scientists have been monitoring the impact climate change is having on vector-borne diseases that are already known to kill millions every year. Malaria is one of the strongest examples of this. Climate change has expanded the range of mosquitoes and birds that are known to carry the parasite responsible for malaria and dengue fever, meaning these sometimes life-threatening diseases are getting the opportunity to interact with more humans. Malaria has a potential two-fold impact on heart disease. While existing heart conditions could trigger complications in people who are exposed to malaria, research suggests that contracting the disease could also cause heart failure in people without a history of heart disease. In one retrospective study, published in December 2019 in Malaria Journal, German researchers analyzed more than 530 adults who had been hospitalized in Berlin for malaria over a 15-year period. They found that people who had hypertension were more likely to develop a severe case of malaria, which can quickly become life-threatening. Other studies have found that malaria can trigger heart problems in people without a history of poor cardiovascular health. One small study, presented at the European Society of Cardiology Congress in September 2019, evaluated nearly 4,000 Danish people who had been infected with malaria between 1994 and 2017. None of these people had a known history of heart failure or heart attack when they were first infected with malaria, however, 69 eventually suffered from heart failure — considered a much higher percentage than the national average. The team concluded that having malaria increased a person’s risk of eventual heart failure — but not heart attack — by 30 percent because the mosquito-borne disease causes inflammation that can lead to scar tissue in the heart. “When the number of parasites in the body increases, they may accumulate in the small vessels of the heart, consequently causing heart attack and affecting the rhythm of the heart,” says Philip Brainin, MD, a postdoctoral research fellow in the Department of Cardiology at Universidade Federal do Acre in Brazil, who co-authored the study, noting that these impacts can usually be reversed with the right care. “But despite effective treatment which eliminates the malaria parasite, there seems to be a persistent long-term risk of developing heart disease,” he says.