Dementia symptoms tend to worsen during heat waves primarily because extreme heat places additional physical and physiological stress on the body, which people with dementia are less able to manage. Several interconnected factors contribute to this decline in cognitive and physical functioning during hot weather.
First, **thermoregulation—the body’s ability to maintain a stable internal temperature—becomes impaired with age and dementia**. Older adults naturally have a reduced capacity to sweat and to increase blood flow to the skin, which are key mechanisms for cooling down. Dementia can further diminish awareness of temperature changes and reduce the ability to communicate discomfort or take actions like drinking water or seeking shade. This leads to a higher risk of overheating and dehydration during heat waves.
**Dehydration is a major driver of worsening dementia symptoms in heat**. When the body loses too much fluid through sweating and is not replenished, blood volume decreases and blood thickens, which can reduce oxygen and nutrient delivery to the brain. Dehydration also causes electrolyte imbalances that affect nerve and muscle function. For people with dementia, who may already have compromised brain function, this can exacerbate confusion, memory loss, agitation, and other cognitive symptoms.
Heat stress also triggers **systemic inflammation and vascular changes**. High temperatures can cause blood vessels to dilate and become more permeable, potentially destabilizing plaques in arteries and increasing the risk of strokes or mini-strokes. Since many older adults with dementia have underlying cardiovascular disease, heat waves can worsen brain blood flow and oxygen supply, leading to acute cognitive decline or delirium.
Certain **medications commonly prescribed to people with dementia or other chronic conditions can increase heat sensitivity**. Diuretics, laxatives, some antidiabetics, and mental health drugs can impair the body’s ability to retain water or regulate temperature, making dehydration and heat exhaustion more likely. This medication effect compounds the natural vulnerabilities caused by aging and dementia.
Environmental factors during heat waves also play a role. Heat waves often coincide with **increased air pollution**, such as smog or wildfire smoke, which can further impair brain function and cardiovascular health. Poor air quality can worsen breathing difficulties and reduce oxygen levels, adding to the stress on the brain.
Beyond the physical effects, heat can also **aggravate behavioral and psychological symptoms of dementia**. Overheating can increase restlessness, agitation, confusion, and anxiety. People with dementia may have difficulty understanding why they feel uncomfortable or may resist efforts to cool down
