Each year, there are about 700 heat-related deaths in the United States. In 2022, 707 Massachusetts residents visited the emergency department (ED) and 87 were hospitalized. In the last decade, heat-related illnesses have caused 30 deaths in Massachusetts.
Age and health status are important risk factors for heat-related illness (HRI). However, social, economic, and environmental factors also play important roles. These factors can be especially impactful during periods of extreme heat. This is because resources for staying cool are not always equitably distributed.
The Intergovernmental Panel on Climate Change (IPCC) is a group of scientists working on climate-related projects for the United Nations. The IPCC predicts that climate change will cause increasing heat waves. We can also expect to see longer warm seasons. In turn, the prevalence of heat-related illness is also expected to grow.
You can use the display to review HRI hospitalization or ED rates for any city or town in Massachusetts.
What is heat-related illness?
Heat-related illness (HRI) is a health condition resulting from exposure to high temperatures. It is sometimes known as heat stress. In these conditions the body becomes unable to properly cool itself. This results in a rapid rise in body temperature. Heat stress can also occur or worsen with physical activity or when accompanied by other diseases. Heat stress has a range of signs and symptoms, described below.
What are the symptoms of HRI?
Symptoms for different types of HRI range from mild to severe. The following symptoms are important warning signs. If you or someone you are around has these symptoms, work swiftly to get them to a cooler place.
Heat stroke
Heat stroke is the most serious heat-related illness. It occurs when the body's temperature rises rapidly and is unable to cool down. Symptoms of heat stroke include:
High body temperature
Headache
Dizziness
Confusion
Nausea
Losing consciousness
Heat exhaustion
Heat exhaustion occurs when the body experiences an excessive loss of the water and salt. Symptoms include:
Heavy sweating
Clammy skin
Fast pulse
Nausea
Muscle cramps and weakness
Headaches
Dizziness
Heat cramps
Heat cramps can occur when the body sweats a lot during strenuous activity, like exercise. Symptoms include muscle pain or spasms.
Heat rash
Heat rash is caused by excessing sweating during hot weather. Symptoms include red clusters of small blisters on the skin.
What causes HRI?
HRI is caused by exposure to high temperatures. High humidity and physical activity can worsen heat stress. Our bodies can regulate our temperature through sweating and other processes. However, when exposed to high temperatures, the body may not be able to cool itself. This will raise the body's core temperature, and we can develop heat stress.
Who is at risk for HRI?
Any individual can develop heat stress if engaged in physical activity or exposed to heat and humidity. The following factors can increase a person’s risk for developing heat stress:
Health
People with chronic health conditions may be more affected by the heat. Common conditions that increase risk include:
Heart disease
Stroke
Kidney disease
Diabetes
Obesity
Age
The elderly can be at greater risk of developing heat-related illness. This is especially true for those who live alone or may have chronic health conditions. These health conditions may make it difficult to regulate body temperature. Prescription medications may also play a role. More information and resources for the elderly and extreme heat can be found at the Executive Office of Aging and Independence – Preparing for Extreme Heat.
The very young can also be especially vulnerable to health impacts. Infants have a more difficult time regulating their body temperature due to their small size. They are also unable to dress themselves and can't make decisions that can help regulate their temperature.
Work-related exposure
Both indoor and outdoor workers can be more likely to be exposed to hot environments. Additionally, these jobs may require increased physical activity. This can increase the risk of developing heat-related illnesses. For more information on occupational risk for heat related illnesses check out the MA Labor and Workforce blog - Best Practices for Preventing Health Illness. It is available in both English and Spanish.
Social factors
We are all impacted by the social determinants of health (SDoH). These are the social, economic, and physical factors where we work, live and play.
Income, living conditions, and the neighborhood you live in can impact a person’s exposure to heat. For example, those experiencing homelessness spend more time outdoors. They may lack resources for reducing heat exposure, especially during summertime. They may also have limited resources to find alternative shelter during a heat wave. Those living with low incomes may not be able to afford air conditioning and live in small spaces. Those who rent may be reliant on a landlord to make changes that could reduce heat exposure.
How can you prevent heat stress and HRI?
Heat-related illnesses and deaths are preventable. Here are some tips for avoiding heat-related illness:
Stay inside in the air conditioning or contact your local health department or locate an air-conditioned shelter in your area
Drink plenty of water
Wear loose, lightweight clothing
Use a buddy system - check on a friend or neighbor, during extreme heat events
Plan outdoor activities during the early morning, late afternoon, and evening hours
Know the signs of heat stress and act quickly if you feel the symptoms or someone you know shows signs
Employers should provide training so workers understand what heat stress is and how it can be prevented
Looking to add a cooling system? Programs like Mass Save may be able to help.
Why does MA EPHT track HRI?
MA EPHT tracks the number of ED visits and hospital admissions due to heat-related illness. These rates are tracked in each community in Massachusetts. The relationship between extreme heat and increased illness and death is well established. Rates for heat-related illness are indicators of the impact of a changing climate. Tracking these data can help document changes of heat exposure over time and place. We can also identify and monitor vulnerable populations. This information allows us to evaluate the results of local climate adaptation strategies. Learn more from the CDC on how extreme heat can impact our health.
Available data
Use the Explore HRI Hospitalization Data link on this page to access the following measures for heat-related illness:
- Annual number of hospitalizations / ED visits
- Annual crude rate per 100,000 population
- Annual age-adjusted rate per 100,000 population
- Explore data in tables, charts, and maps
MA EPHT presents case counts and crude rates on HRI emergency department and hospital admissions for the following geographies: city/town, county, EP region, EOHHS region, and statewide. Measures are offered by a combination of year, age group, and sex. The most current available data is shown. Be sure to check the site periodically as new data is added each year. To protect privacy, no information is shown that could identify an individual.
Related Links
Additional resources
National
- NOAA Heat Wave Brochure: Describes heat-related illness symptoms, first aid, and safety tips; provides information on the National Weather Service Heat Index Program; gives national statistics on heat-related mortality
- OSHA Occupational Heat Exposure pages: Occupational Safety and Health Administration pages with heat-related illness and first aid information specific to workers as well as industry specific resources and standards
- OSHA's Campaign to Prevent Heat Illness in Outdoor Workers: Educational resources and information on preventing heat illness in outdoor workers
- CDC National EPHT Climate Change pages: Landing page for the National Environmental Public Health Tracking pages on climate change related indicators including extreme heat days and events, national heat stress hospitalization data, heat vulnerability measures, mortality data, and temperature distribution by county
- Extreme Heat pages at CDC: CDC’s emergency preparedness and response pages related to extreme heat