The Effect of Heat Waves on Mental Health in a Temperate Australian City
Hansen, Alana, Bi, Peng, Nitschke, Monika, Ryan, Philip, Pisaniello, Dino, Tucker, Graeme, Environmental Health Perspectives
OBJECTIVE: The goal of this study was to identify mental, behavioral, and cognitive disorders that may be triggered or exacerbated during heat waves, predisposing individuals to heat-related morbidity and mortality.
DESIGN: Using health outcome data from Adelaide, South Australia, for 1993--2006, we estimated the effect of heat waves on hospital admissions and mortalities attributed to mental, behavioral, and cognitive disorders. We analyzed data using Poisson regression accounting for overdispersion and controlling for season and long-term trend, and we performed threshold analysis using hockey stick regression.
RESULTS: Above a threshold of 26.7[degrees]C, we observed a positive association between ambient temperature and hospital admissions for mental and behavioral disorders. Compared with non--heat-wave periods, hospital admissions increased by 7.3% during heat waves. Specific illnesses for which admissions increased included organic illnesses, including symptomatic mental disorders; dementia; mood (affective) disorders' neurotic, stress related, and somatoform disorders; disorders of psychological development; and senility. Mortalities attributed to mental and behavioral disorders increased during heat waves in the 65-to 74-year age group and in persons with schizophrenia, schizotypal, and delusional disorders. Dementia deaths increased in those up to 65 years of age.
CONCLUSION: Our results suggest that episodes of extreme heat pose a salient risk to the health and well-being of the mentally ill.
RELEVANCE TO CLINICAL OR PROFESSIONAL PRACTICE: Improvements in the management and care of the mentally ill need to be addressed to avoid an increase in psychiatric morbidity and mortality as heat waves become more frequent.
KEY WORDS: dementia, heat waves, mental health, psychiatric, schizophrenia, temperature, weather. Environ Health Perspect 116:1369-1375 (2008). doi: 10.1289/ehp. 11339 available via http://dx.doi.org/ [Online 30 June 2008]
Compared with the general population, persons with mental health problems often experience poorer overall health with higher rates of morbidity and mortality (Australian Bureau of Statistics 2006). Additionally, it has been well documented that, because of behavioral issues and medications that interfere with physiological homeostasis, those with mental illness are susceptible to the effects of extreme heat, as demonstrated by increases in hospital admissions (Kovats and Ebi 2006; Shiloh et al. 2005) and mortalities (Bark 1998; Basu and Samet 2002; Kaiser et al. 2001; Naughton et al. 2002) associated with heat waves. However, few studies have characterized specific mental and behavioral disorders (MBDs) that may be exacerbated by high temperatures.
Mental illnesses may range from short-term bouts of depression and anxiety to long-term conditions such as developmental impairments, chronic depression, Schizophrenia, or chronic anxiety disorders [Australian Institute of Health and Welfare (AIHW) 2006]. Accounting for an estimated 13% of the national disease burden in Australia, mental illness is among the 10 leading causes of disease in 2003 and has been declared a National Health Priority Area (AIHW 2006). In the State of South Australia, studies have shown that as many as one in five adults has a mental problem (Taylor et al. 1999).
Our aim in this study was to identify mental disorders that contribute to heat-related morbidity and mortality in a temperate climatic region. This study is unique in that to our knowledge, no similar investigation has previously been undertaken. Moreover, we used both hospital admissions and mortality data spanning a 13-year period to establish a comprehensive overview of the temperature-health association. With mental disorders causing an already significant burden on the public health system, understanding the relationship between hot-weather extremes and psychiatric illness will assist in identifying populations at risk as global warming ensues, and provide valuable information for decision makers in the mental health and social service sectors. …