Short-term exposure to particulate matter and apparent temperature is associated with schizophrenia severity in Italy

Schizophrenia is a severe and disabling condition with a multi-factorial etiology. Recent literature hypothesized a role of environmental factors in the onset and course of the disorder. The purpose of the present article is to investigate the association of different air pollutants and apparent temperature (AT) with schizophrenia severity. We conducted a retrospective cross-sectional study on 278 patients with a diagnosis of schizophrenia, who were recruited between 2002 and 2021 in Milan, Italy, for a total of 890 hospital admissions. Demographic, biological, and medical data were obtained from clinical charts and intranet hospital applications. Disorder severity was assessed by the Positive and Negative Syndrome Scale (PANSS). For each subject, exposure to particulate matter (PM) PM_2.5, PM₁₀, and black carbon (BC) on the day of hospitalization and on the previous six days was estimated based on regional monitoring of air quality. AT was also calculated. Associations were assessed by a distributed lag non-linear model approach. Cumulative short-term exposure to particulate pollutants was associated with increased PANSS in the Spring-Summer period (for PM₁₀: β=1.52 (95 % CI: 0.50, 2.55)), with larger single-lag increments when approaching to the day of hospital admission. Instead, increasing AT was associated with schizophrenia worsening only in the Autumn-Winter period, when considering exposure on day 0 (β=0.50 (95 % CI: 0.09, 0.91)) and day -1 (β=0.30 (95 % CI: 0.10, 0.50)). These findings highlight air pollution and AT as modifiable risk factors for schizophrenia severity, particularly during certain seasons, and underscore the need for further research on preventive strategies.