Mentally Ill at Risk in Heat Waves

High temperatures are linked to higher risk of death for those with mental disorders

(RxWiki News) When the temperature climbs into the triple digits outside, death rates can climb as well. Extreme heat waves can be especially dangerous for those with mental disorders.

A recent study has found an increased risk of death among people with certain mental illnesses, including psychosis, dementia and substance abuse, when the temperature becomes excessively hot.

"Keep cool and drink water."

The study, led by Lisa A. Page, PhD, of the Mental Health Liaison Team at Royal Sussex County Hospital in England, looked at the death records and medical histories of people with psychosis, dementia and alcohol or other substance abuse disorders who died between January 1998 and December 2007.

They analyzed a total of 22,562 deaths of people, using the United Kingdom General Practice Research Database. If the patient had been prescribed medication for their condition, the researchers assumed they had been taking it for the purposes of the study.

Page and her colleagues then looked at the average daily temperature and relative humidity data for UK regions from 1998 to 2007. They compared these records to the death rates of the people included in their study, divided by region, age group, diagnosis and the drug types the people had been prescribed.

Just as with the general population, the highest overall mortality rates occurred in winter months. Once the temperature went over 64 degrees Fahrenheit, they saw pattern of increased death rates among those with the disorders they included.

The temperature of 64 degrees corresponds to about the 93rd percentile of daily average temperature for central England.

They found that every increase of 1 degree Celsius in temperature was linked to a 4.9 percent increase in death. Although Celsius and Fahrenheit do not have an exact linear conversion, 1 degree Celsius at hot temperatures (80s and above in F) is approximately 1.5 to 2 degrees Fahrenheit.

The researchers also found patterns related to age and the specific diagnosis of the people they included in the study. Those under age 65 had a greater risk of death during hot weather than those over 65.

The risk of death among the elderly was 4 percent greater for each Celsius degree compared to 10 percent greater per degree for those under 65. These are very small increased risks, but they were significant enough not to be coincidence.

The researchers found that of the three conditions included, alcoholism and other substance abuse carried a slightly higher risk for death during hot weather.

Those taking hypnotic/anxiolytic and antipsychotic medications were about 7 to 8 percent more likely to die during hot weather for each additional degree in Celsius, but no effect was found for those taking antidepressants.

There is a higher increased risk of death among the general population during hot weather as well, which the researchers stated is about 2 percent per 1 degree Celsius.

Therefore those with psychosis, substance abuse disorders and dementia were three percentage points greater in their risk of death during high temperatures.

The authors noted that other factors may account for the higher risk of death among those with mental illness, such as the fact that they may be more likely to be socially isolated or living in an institution, which both increase their risk of death.

These groups may also be in poorer physical health than the general population. Further, people with dementia, for example, may be at higher risk because they are already at a higher risk for wandering alone.

The study did not look at the cause of death among those included, so the researchers could not comment on what types of conditions led to the higher mortality rates.

The study was published in the June issue of the British Journal of Psychiatry. The research was funded by the BUPA Foundation. One author, R. Sari Kovats, PhD, has received funding from the EuroHEAT initiative funded by the World Health Organization and European Union.

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Review Date: 
July 11, 2012