Association of Exposure to Humidex with Schizophrenia Admissions in Qingdao, China: A Time-Series Study

Neuropsychiatr Dis Treat. 2025 Apr 29;21:989-997. doi: 10.2147/NDT.S521191. eCollection 2025.

ABSTRACT

PURPOSE: This study aimed to quantify the effects of humidex (a composite index of temperature and relative humidity) on schizophrenia admissions.

METHODS: The exposure-lag-response relationship between humidex and schizophrenia admissions was explored via a distributed lag nonlinear model (DLNM). The modification effects of sex and age were also investigated. We further calculated the attributable fraction (AF) and number (AN) due to humidex.

RESULTS: During the study period, the median humidex in Qingdao was 15.22, and the low humidex (-7, 2.5th percentile) and high humidex (40, 97.5th percentile) were -7 and 40, respectively. The significant adverse effects of low humidex on schizophrenia admissions persisted from lag 2 [Relative risk (RR)=1.060, 95% CI (confidence interval): 1.006-1.117] to lag 5 (1.063, 1.008-1.122) and reached its maximum at lag 4 (1.078, 1.008-1.152). Females and young individuals are susceptible to low humidex. In addition, the AFs and ANs of schizophrenia admissions due to low humidex were 7.2% and 407, respectively.

CONCLUSION: Schizophrenia admission was associated with only low humidex. Humidex may serve as an early warning indicator of schizophrenia.

PMID:40322724 | PMC:PMC12049671 | DOI:10.2147/NDT.S521191