Daily temperature linked to bipolar admissions

By Mark Cowen

Results from a Taiwanese study suggest that high daily temperatures are associated with increased hospitalization rates for mood symptoms among patients with bipolar disorder, particularly women.

The researchers found that the risk for hospitalization began to increase when the daily temperature rose above 24.0°C, and continued to increase with higher daily temperatures.

The results support "our hypothesis that environmental factors influenced bipolar disorder hospitalizations," comment Huey-Jen Su and team from National Cheng Kung University in Tainan.

The team used data from the Central Weather Bureau of Taiwan and the Psychiatric Inpatient Medical Claim (PIMC) dataset to assess the effects of daily temperature on hospitalization rates for bipolar disorder between 1996 and 2007.

Data on a total of 5461 bipolar disorder patients (9071 bipolar admissions) were included in the analysis.

The researchers found that there was a significant positive association between increasing ambient temperature over 24.0°C and hospital admissions for bipolar disorder the following day.

Specifically, compared with a daily mean temperature ranging from 19.8 to 24.0°C, the relative risk for bipolar disorder admission increased 10%, 15%, 34%, and 51% when the daily mean temperature was over 24.0°C, 27.2°C, 29.0°C, and 30.7°C, respectively.

Women with bipolar disorder were 48% more likely to be admitted to hospital as the temperature increased compared with men, the researchers note.

"This study suggests a relationship between mean diurnal temperature and the risk of bipolar disorder admission," conclude Su et al in Social Psychiatry and Psychiatric Epidemiology.

They add: "Future research should focus on the impact of other environmental variables on psychiatric hospitalization, and specifically on precautionary perspectives on mental health promotion and risk evaluation."

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