People with serious mental illness at increased risk of death in hot weather
By Margaret Rogers
New research adds to the growing evidence that people with mental illness are vulnerable during hot weather. It is suggested that 
people with serious mental illness are at increased risk of death during periods of ‘heat wave’ and this has implications for public health strategies during times of very hot weather conditions.
The study is published in the June issue of the British Journal of Psychiatry. In this study the researchers used the General Practice Research Database to identify people with a diagnosis of psychosis, dementia, alcohol misuse and drug misuse who had died in England over a 10 year period from 1998 – 2007. It was found that there were 22,562 deaths which equates to an average of 6.1 deaths per day. Daily temperature data across the same period of time was downloaded during the same period from all monitoring stations in England from the British Atmospheric Data Centre.
The researchers found that patients with mental illness faced an increased risk of death of about 5% per 1oC increase in temperature above 18oC. This is greater than the risk for the general population, which has an increased risk of around 3% per 1oC increase in temperature.
The increase in risk of death was more pronounced among:
- younger patients
- those who live in southern and eastern parts of England
- those with a diagnosis of drug or alcohol problems
- those who were taking antipsychotics.
The researchers believe there are several biological and social factors that may increase mortality among people with mental illness during hot weather. People with mental illness are more likely to be socially isolated or living in institutional care – both of which are risk factors for heat-related death. Antipsychotic medication can also affect people’s ability to regulate their body temperature by reducing sweating.
The researchers also suggest that people with substance misuse problems may be vulnerable during hot weather because alcohol depresses the central nervous system causing dehydration, and opiates can affect the body’s physiological response to heat.
The researchers were surprised to find that, given that elderly people are often associated with high death rates during heat waves, it was patients under 65 who were at greater risk of death than older patients. However, they believe this may be because the majority of older people in the study had dementia, and may have received better care during periods of hot weather than younger people with alcohol or drug misuse problems.
Consultant psychiatrist and lead researcher Dr Lisa Page, of Sussex Partnership NHS Foundation Trust, said: “We found a marked increase in risk of death for people with psychosis, dementia and substance misuse during hot weather, and suggests that people with mental illness may be a vulnerable group. Some public health strategies, such as the English ‘Heat Wave Plan’ already identify patients with mental health problems as being a high risk group. But more attention may need to be paid to patients with alcohol and drug misuse problems, who are often not under the care of mental health services.”
Senior researcher Professor Louise Howard, King’s College London Institute of Psychiatry added: “Given that global temperatures will continue to rise and the frequency of heat waves is predicted to increase in the years to come, these findings suggest that the consequences of climate change may be felt disproportionately by the mentally ill.”
