Associations of Short-term Exposure to Air Pollution and Ambient Temperature Increase with Psychiatric Admissions in Elderly Adults

Abstract

BACKGROUND AND AIM: Little is known about the associations between ambient environmental exposures and risk of acute episodes of psychiatric disorders. We aim to estimate the risk of acute psychiatric hospital admission associated with short-term exposure to ambient air pollutants and temperature increase in the US elderly population. METHODS: Daily ambient levels of air pollutants (PM2.5, O3, and NO2) and daily ambient surface temperature were assigned to participants by zip code. A time-stratified case-crossover study design was applied to estimate the relative risk increases (RRI) and annual absolute risk differences (ARD) in targeted psychiatric admission rate per 5 units increase in ambient exposures (μg/m³ for PM2.5, ppb for ozone and NO2, °C for temperature). We included all emergency and urgent admissions with primary diagnosis of depression (n=458,492), schizophrenia (n=165,572) and bipolar disorder (n=166,833) from 2000 to 2016 in the entire US Medicare population. RESULTS:Each 5 μg/m³ increase in short-term exposure to PM2.5 was associated with an RRI of 0.62% (95% CI: 0.23%, 1.02%) for depression, an RRI of 0.77% (95% CI: 0.11%, 1.44%) for schizophrenia, and an RRI of 1.19% (95% CI: 0.49%, 1.90%) for bipolar disorder. Each 5 ppb increase in short-term exposure to NO2 was linked with an RRI of 0.35% (95% CI: 0.03%, 0.66%) for depression, as well as an RRI of 0.64% (95% CI: 0.20%, 1.08%) for schizophrenia. For each 5 °C increase in short-term exposure to cold season temperature, relative risk increased by 3.66% (95% CI: 3.06%, 4.26%), 3.03% (95% CI: 2.04%, 4.02%) and 3.52% (95% CI: 2.38%, 4.68%) for depression, schizophrenia and bipolar disorder, respectively. No associations were found with ozone and warm season temperature. CONCLUSIONS:In the US nationwide Medicare elderly population, short-term exposure to elevated levels of PM2.5, NO2 and cold season ambient temperature was significantly associated with increased risk of acute psychiatric admissions. KEYWORDS: Air pollution, Temperature, Mental health outcomes, Short-term exposure, Multi-pollutant