Periods of extreme heat can significantly worsen a range of chronic health conditions, increasing the risk of emergency medical visits and fatalities, experts say. Research points to vulnerable groups including individuals with cardiovascular, respiratory, metabolic, and neurological diseases who face greater challenges during heat waves due to the strain heat places on already compromised bodily systems.
According to Robert Meade, a research fellow at the Harvard T.H. Chan School of Public Health, heat exposure can exacerbate health issues in two primary ways. First, underlying health problems may reduce the body’s capacity to regulate temperature, raising susceptibility to heat exhaustion or heat stroke. Second, elevated temperatures can trigger flare-ups or worsen symptoms even in the absence of overt overheating.
Arthritis sufferers may experience intensified joint pain and swelling when extreme heat combines with high humidity, as inflammation tends to rise under these conditions. Similarly, people with gout might see symptom aggravation due to dehydration increasing the concentration of uric acid, facilitating the formation of painful joint crystals.
Heat also has notable effects on kidney-related conditions. Higher temperatures correlate with surges in kidney stone incidents because dehydration concentrates minerals that contribute to stone formation. For those with chronic kidney disease, heat can hasten kidney function decline, partly due to shifts in blood flow during the body's efforts to cool down.
Respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD) are also impacted by heat. Hot and either humid or arid air can irritate the airways, escalating the likelihood of attacks. Further compounding risks, high-temperature periods often coincide with poor air quality, creating an environment conducive to respiratory flare-ups.
Emerging data also highlight heat sensitivity in autoimmune disorders such as lupus, with symptoms including rash, joint pain, and blood abnormalities flaring in response to warm weather and humidity. People with diabetes may face challenges maintaining stable blood sugar levels during heat waves, potentially leading to increased complications and mortality. Heat sensitivity in multiple sclerosis patients frequently results in temporary worsening of fatigue, weakness, numbness, and cognitive difficulties.
Cardiovascular disease patients are particularly vulnerable as elevated temperatures place extra stress on the heart, which must work harder to dissipate heat. This can worsen conditions such as coronary artery disease and heart failure and raise the risk of heart attacks and strokes. Heat-related triggers may also provoke migraine attacks, especially due to temperature fluctuations and exposure to bright sunlight.
Mental health outcomes may deteriorate during heat waves as well, with evidence linking hot weather to spikes in emergency visits for depression and anxiety and a rise in suicide rates. Stress responses, feelings of loss of control, and disrupted sleep patterns are thought to contribute to these trends.
Health experts recommend several strategies to manage symptoms during hot weather. Maintaining hydration, using air conditioning or fans, and wearing breathable clothing are key preventive measures. Patients are advised to consult healthcare providers ahead of heat waves to review medications and establish plans for managing potential flare-ups. Avoiding other known triggers, including missed meals and inadequate sleep, is also recommended to reduce the risk of heat-related complications. Vigilance and preparedness remain essential for those with chronic conditions facing increasingly frequent and severe heat episodes.