The role of psychotropics on the associations between extreme temperature and heat-related outcomes among people with mental health conditions: population-based study.

BACKGROUND

The association between heatwave and heat-related outcomes in people with mental health conditions with and without psychotropics was unclear.

METHODS

We identified people with severe mental illness (SMI) and depression, respectively, using Japanese claim data of Ibaraki prefecture during 1/1/2014-31/12/2021. We conducted self-controlled case series to estimate the incidence rate ratio (IRR) of heat-related illness, myocardial infarction and delirium, respectively, during 5-day pre-heatwave, heatwave, and 5-day post-heatwave periods v. all other periods (baseline) within an individual, stratified by periods prescribed psychotropics and periods not prescribed psychotropics, respectively.

RESULTS

Among people with SMI, heatwave was associated with an increased rate of heat-related illness v. baseline, with no evidence of a difference in the IRRs between those prescribed v. not prescribed antipsychotics (IRR: 1.48 [95% CI 1.40-1.56]; 1.45 [95% CI 1.35-1.56] respectively, p interaction: 0.53). Among people with depression, heatwave was similarly associated with heat-related illness, with no evidence of a difference in the IRRs between those prescribed v. not prescribed antidepressants (IRR: 1.54 [95% CI 1.46-1.64]; 1.64 [95% CI 1.57-1.71] respectively, p interaction: 0.33). Smaller increased rates of heat-related illness were also observed in pre- and post-heatwave periods, v. baseline in both cohorts. There was weak evidence of an increased risk of MI and delirium associated with heatwave v. baseline.

CONCLUSIONS

We showed an increased risk of heat-related illness, myocardial infarction and delirium associated with heatwave in people with mental health conditions regardless of whether being prescribed psychotropics. Risks of heat-related illness, myocardial infarction and delirium associated with heatwave might not be factors to influence decisions about the routine use of psychotropics.