Impact of heat on mental health emergency visits: a time series study from all public emergency centres, in Curitiba, Brazil

Abstract

Objectives: Quantify the risk of mental health (MH)-related emergency department visits (EDVs) due to heat, in the city of Curitiba, Brazil.

Design: Daily time series analysis, using quasi-Poisson combined with distributed lag non-linear model on EDV for MH disorders, from 2017 to 2021.

Setting: All nine emergency centres from the public health system, in Curitiba.

Participants: 101 452 EDVs for MH disorders and suicide attempts over 5 years, from patients residing inside the territory of Curitiba.

Main outcome measure: Relative risk of EDV (RR_EDV) due to extreme mean temperature (24.5°C, 99th percentile) relative to the median (18.02°C), controlling for long-term trends, air pollution and humidity, and measuring effects delayed up to 10 days.

Results: Extreme heat was associated with higher single-lag EDV risk of RR_EDV 1.03(95% CI 1.01 to 1.05-single-lag 2), and cumulatively of RR_EDV 1.15 (95% CI 1.05 to 1.26-lag-cumulative 0-6). Strong risk was observed for patients with suicide attempts (RR_EDV 1.85, 95% CI 1.08 to 3.16) and neurotic disorders (RR_EDV 1.18, 95% CI 1.06 to 1.31). As to demographic subgroups, females (RR_EDV 1.20, 95% CI 1.08 to 1.34) and patients aged 18-64 (RR_EDV 1.18, 95% CI 1.07 to 1.30) were significantly endangered. Extreme heat resulted in lower risks of EDV for patients with organic disorders (RR_EDV 0.60, 95% CI 0.40 to 0.89), personality disorders (RR_EDV 0.48, 95% CI 0.26 to 0.91) and MH in general in the elderly ≥65 (RR_EDV 0.77, 95% CI 0.60 to 0.98). We found no significant RR_EDV among males and patients aged 0-17.

Conclusion: The risk of MH-related EDV due to heat is elevated for the entire study population, but very differentiated by subgroups. This opens avenue for adaptation policies in healthcare: such as monitoring populations at risk and establishing an early warning systems to prevent exacerbation of MH episodes and to reduce suicide attempts. Further studies are welcome, why the reported risk differences occur and what, if any, role healthcare seeking barriers might play.

Keywords: ACCIDENT & EMERGENCY MEDICINE; Health Services; MENTAL HEALTH; PUBLIC HEALTH.

Figure 1

Brazilian territory shown in grey, with inset of the city of Curitiba (435 036 km²) and of its metropolitan region. The nine blue circles represent all the public emergency units (UPAs) in the city; the three black pins indicate the meteorological stations from where data of temperature and humidity were used; the two red pins show the meteorological sites from where air pollution data were retrieved. Variables retrieved from each monitoring site: 1. REPAR: O3 and PM10, 2. INMET Curitiba: Tmean, 3. Simepar Curitiba: Tmean and humidity, 4. Boqueirão: O3 and PM10 and 5. INMET Colombo: Tmean and humidity. The owners of the monitoring sites were: 1. Petrobras, 2 and 5: National Brazilian Meteorological Institute; 3. Paraná Environmental Monitoring and Technology System; 4. Water and Earth Institute. Source: authors. Image partly created using Mapbox.com. Met. Station, meteorological stations; T, temperature.

Figure 2

Cumulative effects of temperature on RR for an EDV calculated for short-term (lagCUM 0–6 days (A) and long-term (lagCUM 0–10 (B), respectively. Reference Tmean: 18.02°C. Grey area represents the 95% CI, blue dotted lines are the extreme (P1) and moderate (P5) cold, while red dotted lines are the extreme (P99) and moderate (P95) heat. EDV, emergency department visit; RR, relative risk.

Figure 3

Extreme heat effect (P99, daily Tmean 24.5°C) over different subgroups, during different lags. Tmean reference: 18.02°C. Subgroups formed for analysis were (A) MH total, (B) female, (C) male, (D) age from 0 to 17 years old, (E) age from 18 to 64 years old and (F) elderly ≥65 years old. P, percentile. Grey area represents 95% CI. EDV, emergency department visit; MH, mental health; RR, relative risk.

Figure 4

Three-dimensional graphs of the relationship among heat (x), RREDV (y) and lag (z) for (A) MH in general, (B) neurotic disorders and (C) suicide attempt. Tmean reference: 18.02°C. MH, mental health; RREDV, relative risk of emergency department visit.