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A Salvation Army EMS vehicle is setup as a cooling station as people line up to get into a splash park while trying to beat the heat in Calgary, on June 30, 2021.Jeff McIntosh/The Canadian Press

As temperatures climb in parts of the country, Environment Canada is issuing heat warnings advising people to take precautions to protect themselves and others, but there’s one group that tends to be especially vulnerable in sweltering weather: those with schizophrenia.

People with schizophrenia, who make up about 1 per cent of the population, need to be aware of their elevated risk of heat-related death, according to Michael Lee, an environmental epidemiologist at the British Columbia Centre for Disease Control. One of the most important things others can do for them is to check in on them when temperatures soar, he said.

Dr. Lee is the lead author of a study, published earlier this year, that found people with schizophrenia had the highest risk of death in B.C. in the summer of 2021, during a record deadly heat dome that enveloped western North America. There are several hypotheses explaining why those with schizophrenia are at higher risk, including social isolation, economic marginalization and antipsychotic medication that affects the body’s ability to regulate heat, Dr. Lee noted.

In the study, published in the journal GeoHealth, he and his colleagues found 134 people with schizophrenia died, representing about 8 per cent of all deaths in the province, during the hottest eight-day period of the heat dome. They found the risk of death for someone with schizophrenia was three times higher, or 207 per cent, than it was during the same period in previous, typical years.

This was greater than any of the 25 other chronic conditions the researchers examined. By comparison, the risk for people with chronic kidney disease and ischemic heart disease increased 36 per cent and 18 per cent, respectively, during the heat dome.

“That’s striking and surprising,” Dr. Lee said of the findings, because while it’s well known that people with chronic kidney disease and ischemic heart disease are at greater risk of heat-related death and illness, “up until this point, schizophrenia just hasn’t been a well-recognized risk factor and it really hasn’t been a part of public health messaging about extreme heat.”

People with schizophrenia were also disproportionately affected by a heat wave in 2018 that killed 66 people in Montreal, according to a 2019 report by the city’s health authority. Of those deaths, 17, or 28.5 per cent, were among people with schizophrenia disorders, whereas the estimated prevalence of schizophrenia in Montreal’s population is only 0.6 per cent.

Schizophrenia is often associated with a condition called anosognosia, where a person lacks insight into their own health status, Dr. Lee explained in an interview. So, during an extreme heat event, people with this condition may not recognize they’re overheating and take measures to cool down.

People with the mental illness may also have other chronic diseases, such as substance use disorder, diabetes and hypertension, which contribute to their risk.

In a separate opinion paper, published in the BC Medical Journal last month, Dr. Lee and his team cited pharmacy data that showed 80 per cent of all people with schizophrenia who died during the 2021 heat dome had been dispensed an antipsychotic medication – which can disrupt the body’s ability to regulate heat – in the 90 days prior.

It’s important to note, however, that antipsychotic medications are considered an unmodifiable risk factor, since they are critical for the management of schizophrenia, Dr. Lee said.

Instead, the focus should be on reducing other risk factors that can be modified, such as social isolation and economic marginalization, he said. According to a B.C. Coroner’s Service review of the heat-related deaths during the 2021 heat dome, 98 per cent of all deaths occurred indoors in a residence, and 56 per cent were among people living alone.

“One of the ways that we can make a big difference moving forward is to increase social connectedness for people with this condition,” Dr. Lee said, such as having family, friends and health care workers check in on them and help find places to keep cool in extreme heat.

The body's ideal internal temperature is 36.9 degrees Celsius. As core temperatures rise, our internal regulation turns to acute self-preservation that leaves the body vulnerable in many ways. Symptoms of heatstroke set in above an internal temperature of 40 degrees Celsius.

Some of these factors that put people with schizophrenia at greater risk during heat waves may be, in part, why they can also be more vulnerable to other harms. People with schizophrenia and other psychotic disorders, for example, were five times more likely to die from COVID-19 than people without severe mental illness, according to a University of Manchester-led study published in Molecular Psychiatry in 2021.

Through her research, Michelle Blumberg, a PhD student in clinical neuropsychology at York University, encounters a subset of people with schizophrenia who are among the most marginalized in society. In a sample of 400 homeless and precariously housed people in Vancouver, she found a disproportionately high amount – 56 per cent – had schizophrenia or other psychotic illnesses.

A lack of adequate shelter makes it not only more difficult for them to cope with extreme heat, but other disasters, such as extreme cold weather and wildfire smoke, as well, she said.

Chris Summerville, chief executive officer of the Schizophrenia Society of Canada, also emphasized the need for quality, affordable housing with air conditioning, and for access to timely mental health supports and services.

“The bigger issue is, how do we respond to people with a mental illness who need our help?” Mr. Summerville said. “I think we just need, as a caring and compassionate society, to take care of the more vulnerable.”

With reports from Tu Thanh Ha

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