Heat waves pose unique threats to people with Parkinson’s and dementia

With 2024 set to end as Earth’s hottest year on record — breaking the previous record set in 2023 — a UCLA Health researcher says people with neurodegenerative diseases will be especially vulnerable to worsening heat waves due to a higher risk of heat-related complications.

In a commentary published in JAMA Neurology, Dr. Indu Subramanian that doctors have a duty to increase understanding of heat-related impacts for people living with diseases such as dementia or Parkinson’s disease and to develop updated solutions to protect these vulnerable patients in a warming world.

This editorial makes clear that these deaths are preventable and that doctors can make a difference.”

Dr. Indu Subramanian

While more frequent and severe heat waves pose health risks to all people who experience them, their effects can be worsened in people with neurodegenerative diseases due to symptoms or treatments associated with them, Subramanian said.

Heat has been shown to worsen symptoms of neurodegenerative diseases. In Parkinson’s disease, symptoms such as a poorly functioning autonomic nervous system can increase the risk of dehydration, heat stroke and fainting, caused by reduced blood flow to the brain. Symptoms of Parkinson’s disease and other conditions can also compromise sweating, which only worsens, especially in areas with high humidity. Subramanian said worsening symptoms can affect a person’s ability to perform regular activities, such as taking medications, turning on air conditioners, rehydrating or taking a cold shower to stay cool.

Some medications that treat these diseases, such as anticholinergics and tricyclics, can inhibit functions such as sweating and blood flow to the skin, passively cooling the body.

A 2020 study led by the University of Malta found statistically significant increases of more than 10% in both mortality from Parkinson’s disease and hospitalizations at temperatures just 1 degree Fahrenheit above a threshold of 93 degrees Fahrenheit. A separate 2019 study from Queensland University of Technology cited by Subramanian found similar trends for patients with Alzheimer’s disease.

The Queensland University of Technology study also found a link between heat-related mortality and the amount of green space near a person’s home. Green space works to prevent heat islands by providing shade, deflecting radiation and releasing moisture. The study found that people who live near little green space have three times the risk of heat-related death.

As the U.S. population of older residents increases, so does the number of people with neurodegenerative diseases such as dementia. Thermoregularity, the ability to maintain body temperature, is often compromised in the elderly. Heat-related complications are also more common in men, although the reason for this increased risk is still unclear, Subramanian said. Increasing social isolation among older adults may also increase the risk of heat-related problems due to a lack of early detection.

“I was surprised how many patients see us, doctors or caregivers, as their only point of contact with the world outside their home,” Subramanian said.

To address these many issues, Subramanian argues that medical providers and institutions should establish best practice guidelines and link these quality measures to reimbursement and certification. An example would be to have doctors regularly screen people with neurodegenerative diseases for social isolation and connect them to resources. The increased use of telemedicine can also be used to allow medical providers to check in on high-risk patients and proactively contact them during periods of high temperatures, Subramanian said. Doctors can take early steps by providing patients with information and resources early.

“People with Parkinson’s disease and dementia are at risk of dying from heat waves and we can be proactive to prevent this,” Subramanian said.

The main article was co-authored by Dr. Ali Saad of the University of Colorado, Aurora, one of the few neurologists to have done a Climate Change Fellowship. Dr. Subramanian is also certified in Integrative Medicine.