Objective To explore the association of single and mixed exposures to air pollutants with the early neuropsychiatric health of the elderly and to further investigate the interaction between air pollution and temperature.

Methods A multicenter, fixed-cohort study was conducted among elderly subjects aged 60 to 65 years in four locations: Baotou and Hohhot in Inner Mongolia Autonomous Region, and Langfang and Shijiazhuang in Hebei Province (approximately 40 subjects were recruited per location). A random intercept multilevel Logistic regression model was used to investigate the impact of single air pollutant exposure on the early neuropsychiatric health of the elderly; further, the pollutants that produced key effects in the mixed air pollutant exposure were identified based on the actual exposure environment, and the interaction effects of air pollution and temperature on the early neuropsychiatric health of the elderly were further analyzed.

Results For every 1 μg/m³ increase in NO₂ and PM_2.5 exposure, the risk of anxiety disorders in the elderly increased by 3.60% (odds ratio OR=1.036 0; 95%CI: 1.030 7-1.041 3) and 2.43%(OR=1.024 3, 95%CI: 1.019 2-1.029 5). In the mixed air pollutant exposure, SO₂ was the primary contributing factor with weights of 0.60, 1.00, and 0.51 for anxiety disorders, depressive disorders, and sleep disorders, respectively. For cognitive impairment, PM₁₀ was the primary contributing factor with a weight of 0.50. The interaction effects of SO₂ and temperature on anxiety disorders were particularly significant: when exposed to high concentrations of SO₂ and high temperatures simultaneously, the risk of anxiety disorders in the elderly increased by 61.73% (OR=1.617 3; 95%CI: 1.602 2-1.632 6), and the relative excess risk due to interaction was 0.035 8 (95%CI: 0.016 7-0.055 0). The higher the temperature, the greater the harm of SO₂ to the anxiety disorders of the elderly. SO₂ and temperature had a significant synergistic effect on the anxiety disorders of the elderly.

Conclusion NO₂ and PM_2.5 are associated with anxiety disorders in the elderly; SO₂ and particulate matter are the primary key factors for the early neuropsychiatric health of the elderly. Most importantly, SO₂ and temperature have an interaction effect on the anxiety disorders of the elderly. The study provides epidemiological evidence for exploring the impact of combined environmental exposures on the early neuropsychiatric health of the elderly.