Heat can trigger acute events (a bad day becomes an ER visit). But long-term exposure can also shape cardiovascular risk indirectly.

In the short term, heat can lower blood pressure due to vasodilation. But repeated dehydration, sleep disruption from hot nights, and stress-hormone activation can destabilize overall blood pressure control.

Poor sleep is linked with higher sympathetic tone (stress response), worse glucose control, and higher blood pressure. If heat islands keep bedrooms warm at night, sleep fragmentation rises—especially in older adults with sleep apnea or heart failure.

Electrolyte changes (sodium, potassium, magnesium), dehydration, and higher catecholamines (stress hormones) can increase palpitations. Atrial fibrillation can be more symptomatic in heat, and medications like diuretics may amplify electrolyte loss.

CDC notes that more than 700 people die from extreme heat every year in the United States (a widely cited figure in CDC public guidance). (CDC)

A large U.S. analysis of the contiguous United States (2008–2017) reported that extreme heat days were associated with higher adult cardiovascular mortality rates. (PMC)

A more recent review focused on aging in a hotter environment reported:

• Cardiovascular mortality increased by 0.12% among older adults for each additional extreme-heat day per month, and
• This corresponded to ~5,000 excess cardiovascular deaths attributed to extreme-heat days from 2008–2017. (PMC)

NIH reporting on a supported study indicates that cardiovascular-related deaths due to extreme heat are expected to increase in the United States between 2036 and 2065. (National Institutes of Health)

The underlying modeling work in Circulation similarly projects increases in extreme heat–associated cardiovascular deaths, with larger projected increases among older adults. (ahajournals.org)

Heat waves affect whole regions, but urban heat islands can make certain neighborhoods hotter than others. That means two older adults in the same metro area can have different exposures.

A 2023 study on urban heat island intensity and cardiovascular impacts found that extreme heat increased cardiovascular morbidity risk and burden in older urban populations, and heat islands exacerbated those impacts—especially among already vulnerable groups (including older ages and chronic conditions).

Urban structures store heat. When nights stay hot, older adults don’t cool down. Cumulative heat stress increases dehydration risk and worsens sleep, compounding cardiac strain.

Signs to watch for 

These symptoms can be heat illness, heart strain, medication effects, or a mix:

Mild-to-moderate warning signs 

• Unusual fatigue or weakness
• Dizziness or lightheadedness when standing
• Headache
• Nausea
• Muscle cramps
• Swelling in ankles/feet
• Palpitations or “fluttering”
• Shortness of breath beyond baseline

When symptoms are an emergency

CDC’s heat illness guidance describes heat stroke as a medical emergency when the body can’t control temperature and it rises rapidly—this can cause permanent disability or death without urgent treatment. (CDC)

Medications as cause

Many common drugs change hydration, sweating, and circulation. Examples include:

• Diuretics (“water pills”)
• Beta blockers (may limit heart rate response)
• ACE inhibitors/ARBs (blood pressure)
• Anticholinergics (reduce sweating)
• Some antidepressants and antipsychotics (thermoregulation effects)

EPA highlights that aging and some medications can alter heat responses. (EPA)

CDC recommends clinicians and patients create a Heat Action Plan and use heat-risk forecasts during warm months.

A practical plan includes:

• A cooling location (home AC, library, mall, senior center)
• Hydration routine (with clinician guidance if heart failure/CKD)
• Medication review for summer (especially diuretics)
• Symptom thresholds for calling family/doctor
• A check-in buddy system

Cool your home

• Keep blinds/curtains closed on sun-facing windows
• Use fans strategically
• Sleep in the coolest room
• Consider a window AC unit for the bedroom if whole-home cooling isn’t possible

What to do 

• Avoid strenuous activity mid-day
• Shift walks to early morning
• Take cool showers or use cool compresses
• Choose light, breathable clothing

WHO’s heat advice emphasizes staying out of the heat and paying attention to unusual symptoms—especially for older adults and those with heart disease. (World Health Organization)

General advice is “drink water,” but some older adults have fluid restrictions. The safe approach:

• Ask your clinician for a heat-day fluid plan,
• Monitor weight (rapid gains/losses),
• Watch for swelling, breathlessness, dizziness.

How to use public tools

• Use CDC’s Heat Risk guidance for planning (health-based heat forecast).
• Use Heat.gov’s older adult risk guidance for practical steps and risk context. (heat.gov)
• Follow CDC heat-health basics during events.