New study finds people with schizophrenia were at higher risk during B.C.’s 2021 heat dome

New research suggests people with schizophrenia, their families and support networks should be on alert during extreme heat events and take precautions because of increased risk.

The study, published this week in GeoHealth, looked at the risk of death for people with different chronic conditions in British Columbia during the heat dome that hit the Pacific Northwest in early summer 2021. It compared deaths during the heat dome with deaths during the same period in previous years, and it found a three-fold increase among people with schizophrenia.

"This study was conducted to understand who is most at risk, so we can prepare for future heat events, which will be more frequent and more severe in the coming decades because of climate change," said Michael Lee, lead author and epidemiologist with Environmental Health Services at the BC Centre for Disease Control (BCCDC). "Climate change has real impacts on our health, and we can help limit those impacts when we know what they are and how to prepare."

The study compared the prevalence of 26 chronic conditions among people who died during the eight-day period of the 2021 heat dome, during which B.C. saw an increase in population mortality, with people who died on the same dates in the nine previous years. It found that mental illnesses were among the conditions that left people most susceptible to death. Those with schizophrenia were at the highest risk. 

There are overlapping risk factors that likely all play a role in increasing the risks for people with schizophrenia. Schizophrenia often includes psychotic symptoms, such as hallucinations, delusions and thought disorders, as well as cognitive losses. Many people living with schizophrenia also suffer from anosognosia or lack of insight into their own illness. Schizophrenia may also lead to social isolation and lower socioeconomic status, and both are risk factors for death during extreme hot weather. In addition, some medications used to treat schizophrenia can play a role in overheating. 

“As demonstrated by the recent research, because individuals living with schizophrenia are more susceptible to heat-related illness, it is essential that families and caregivers are aware of the increased risk, identify potential risk factors and take prompt action to help their loved one during a heat wave,” said Faydra Aldridge, Chief Executive of Officer of the B.C. Schizophrenia Society (BCSS). “Educating ourselves to recognize symptoms of heat-related illness and take emergency cooling measures will help ensure everyone’s safety during heat waves.”

It is important for people with schizophrenia and their support networks to be aware of these risks, so they can take preventative measures.

"Most injuries and deaths during extreme heat events occur indoors due to unsafe temperatures,” said Sarah Henderson, scientific director of Environmental Health Services at BCCDC. “We all have a responsibility to check in on our loved ones and neighbours during extreme weather events, especially if they don’t have access to air conditioning. Strong social and community connections can help mitigate the risks."

The study also found higher risk for people who use substances and for people with conditions such as chronic kidney disease, ischemic heart disease, chronic obstructive pulmonary disease, and diabetes, most of which are well-recognized risk factors during extreme heat. 

“This study will help increase awareness about the risks of extreme heat for people with mental illnesses, so we can address them in our warnings when we prepare for future events,” said Henderson. 

The BCCDC is working with groups, including the BC HEAT committee, regional health authorities, BC Mental Health and Substance Use Services and BC Schizophrenia Society to prepare for future heat emergencies.