A positive relationship between ambient temperature and bipolar disorder identified using a national cohort of psychiatric inpatients

Objective: This study characterizes the positive relationship between daily temperature and bipolar disorder in a cohort of Taiwanese psychiatric inpatients. Methods: Meteorological data, provided by the Central Weather Bureau (CWB) of Taiwan, were interpolated to create representative estimates of mean diurnal temperatures for 352 townships. Psychiatric inpatient admissions enrolled in the national health-care insurance system were retrieved from the 1996-2007 Psychiatric Inpatient Medical Claim (PIMC) dataset. The generalized linear mixed models with Poisson distribution were used to evaluate the relative risks of mean diurnal temperature with respect to increased admissions for bipolar disorder, while adjusting for internal correlations and demographic covariates. Results: Increased relative risks of bipolar disorder admissions were associated with the increasing trends of temperature over 24.0 C (50th ‰), especially for adults and females. The highest daily diurnal temperatures above 30.7 C (99th ‰) had the greatest risks of bipolar hospitalizations. Conclusion: Understanding the increase of bipolar disorder admissions occurring in extreme heat is important in the preparation and prevention of massive recurrences of bipolar episodes.