Heat and Older Adults: What Pharmacists Need to Know

Extreme heat events are a series of days that are much hotter than average for a specific geographic area.¹ These events are becoming more common and severe in the United States—and are expected to increase in the future.¹ Although any person can be at risk for adverse health outcomes due to extreme heat events, there are certain populations who are more prone to experience negative effects from excessive heat, including pregnant patients, pediatric patients, patients with chronic conditions or taking certain medications, and patients older than 65 years of age.^1,2

Older adults are more prone to dehydration.³ This is due to age-related pathophysiologic factors and the presence of chronic illnesses.³ Underlying reasons include alternation in body composition, impairment in renal function and urine concentration ability, and response to thirst triggers.^3,4

The majority of water loss occurs through the respiratory tract, skin, and kidneys.⁴ Older adults experience a more significant loss of hydration status due to overt loss of collagen in the skin throughout the aging process.⁴ Throughout the aging process, body composition and the distribution of fat, water (ie, plasma), and lean muscle change in the older adult, with the total body water decreasing significantly in percentage.⁴ Renal function also decreases with advancing age due to the decline in functioning glomeruli, renal blood flow, and tubular functions.^4,5

The maintenance of total body water balance is achieved via 2 mechanisms: thirst sensation and antidiuretic hormone.^3,5 Normally, through either significant water loss (for example, illness) or inadequate water intake, the body experiences an increase in serum osmolality.⁵ This increase in serum osmolality triggers a message that is relayed to the brain to indicate the individual should consume more water.⁵ The response to increasing serum osmolality and resultant thirst sensation is decreased in the older adult.⁵ Antidiuretic hormone (ADH) is stored within the pituitary gland and is triggered to release in response to increasing serum osmolality.⁵ Once ADH is released, the renal system responds by decreasing the urinary excretion of free water and the volume of urine.⁵ In younger adults ADH is an essential component of maintaining water homeostasis in the body.⁵ Unfortunately, in the older adult, ADH secretion and secondary response in the kidney are often impaired, resulting in an inability to concentrate the urine and an overt loss of water and predominantly sodium in the urine.⁵

The presence of chronic illnesses such as cognitive impairment, dementia, and/or delirium contributes significantly to the risk of dehydration in the older adult.^3,5 The inability to recognize personal needs such as thirst and recall how to access water can contribute to dehydration risk. In addition, mobility and functional limitations may create challenges in accessing water while uncontrolled health conditions such as diabetes increase glucose secretion in the urine, further contributing to the loss of water.⁵ Treatment of hypertension with diuretics and angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers (ACE/ARB) all contribute to a decrease in blood pressure while contributing to urinary water loss (diuretics) and an additional decrease in thirst response. Beta blockers also decrease sweating and a reduction in superficial vasodilation.⁶

Consequently, pharmacists must also be aware of the types of medications that may make patients more susceptible to the effects of heat or increase sun sensitivity.⁶ Both prescription (for example, the aforementioned drugs, anticholinergic agents, and certain psychotropic medications) and OTC medications (for example, aspirin) can increase risk from heat.⁶ Polypharmacy, more prevalent among older patients, adds to the concern.⁶ Pharmacists can review medications that increase risk from heat and can help patients and caretakers develop a heat action plan (including a medication plan) for hot days in collaboration with other members of the care team.⁶ During extreme heat events, medications or other interventions (such as fluid restrictions) may need to be adjusted.⁶

Pharmacists frequently provide care beyond dispensing medication and serve as vital, accessible health care providers for older adults in the community. Therefore, they can also raise awareness and provide patient education on this important topic. Informing patients to stay safe, cool, and hydrated on hot days is of utmost importance for those 65 years and older since they are more predisposed to heat-related problems.⁷ The CDC Heat and Your Health website provides practical tips that include staying in air-conditioned buildings; drinking plenty of water throughout the day, independent of thirst response, as long as the patient’s fluid intake is not limited; not using the stove or oven to cook; wearing lightweight clothing; avoiding vigorous activities and getting plenty of rest; and ensuring the patient is checked by friends or neighbors at least twice a day during heat waves.⁸ Patients should be educated on the symptoms of heat-related illness and on seeking medical care immediately.⁸

Additionally, pharmacists can be prepared by checking their local news and entering their zip code on the CDC Heat Risk Dashboard to check the forecast and recommended actions needed to keep older adults safe.⁹ Pharmacists can also assess the patient’s risk by utilizing the CDC HEAT: A Heat and Health Risk Factor Screening Questionnaire and create an individualized plan for the patient.¹⁰ Questions focus on Housing & indoor environment, Emergency preparedness, Awareness of health risks, and Temperature & outdoor environment.¹⁰ Lastly, providing guidance on proper storage of medications, not leaving medications in hot vehicles or places that are excessively hot, and applying sunscreen while taking medications that increase sun sensitivity are also practical tips to share with older adults.⁶ Through medication review and patient or caregiver counseling, pharmacists can play an important role in ensuring their older patients stay safe during extreme heat events.

Read the other installments:

Heat and Human Health: What Pharmacists Need to Know

Heat and Medications: What Pharmacists Need to Know

REFERENCES

1. U.S. Environmental Protection Agency. Climate change and extreme heat: What you can do to prepare. EPA 430-R-16-061. October 2016. Accessed April 20, 2026. https://www.epa.gov/sites/default/files/2016-10/documents/extreme-heat-guidebook.pdf

2. Centers for Disease Control and Prevention. Clinical overview of heat. September 18, 2025. Accessed April 20, 2026. https://www.cdc.gov/heat-health/hcp/clinical-overview/index.html

5. Taylor K, Tripathi AK. Adult dehydration. In: StatPearls. March 5, 2025. Accessed April 20, 2026. https://www.ncbi.nlm.nih.gov/sites/books/NBK555956/

4. Delafuente JC, Pharmacokinetic and pharmacodynamic alterations in the geriatric patient. Consult Pharm 2008;23:324-34.

5. Li S, Xiao X, Zhang X. Hydration status in older adults: Current knowledge and future challenges. Nutrients. 2023;15(11):2609. doi:10.3390/nu15112609

6. Centers for Disease Control and Prevention. Heat and medications: Guidance for clinicians. September 18, 2025. Accessed April 20, 2026. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html

7. Centers for Disease Control and Prevention. Heat and older adults. June 25, 2024. Accessed April 20, 2026. https://www.cdc.gov/heat-health/risk-factors/heat-and-older-adults-aged-65.html

8. Centers for Disease Control and Prevention. About heat and your health. July 25, 2025. Accessed April 20, 2026. https://www.cdc.gov/heat-health/about/index.html

9. Centers for Disease Control and Prevention. HeatRisk. Accessed April 20, 2026. .https://ephtracking.cdc.gov/Applications/HeatRisk/

10. Centers for Disease Control and Prevention. HEAT: A heat and health risk factor screening questionnaire. June 18, 2024. Accessed April 20, 2026. https://www.cdc.gov/heat-health/hcp/clinical-guidance/HEAT-screening-questionnaire.html