Abstract
BACKGROUND: Urban heat island (UHI), attributed to rapid urbanization, might be a latent modifiable risk factor for human health, yet little is known about whether UHI puts a strain on public mental health. This study aimed to assess the effect of the summer UHI on mental health.
METHODS: Leveraging 338,363 urban residents from the UK Biobank, this study estimated the associations of summer UHI effect with incidence risks of mental disorders, substance use disorder, depressive disorder, and anxiety disorder using both time-independent and time-dependent Cox regression models with full adjustment for possible confounders. Furthermore, the effect of UHI on related psychiatric symptoms and brain microstructure were explored through logistic regression models and multiple linear regression models, respectively.
RESULTS: In this study, summer UHI was significantly associated with the elevated risks of psychiatric disorders. The hazard ratio with a 95% confidence interval (CI) from the time-dependent Cox model was 1.04 (95% CI, 1.03-1.05) for mental disorders, 1.12 (1.11-1.14) for substance use disorder, 1.08 (1.06-1.10) for depressive disorder, and 1.06 (1.04-1.08) for anxiety disorder per standard deviation of UHI intensity, respectively. Subgroup analyses showed that females and individuals with hypertension or coronary artery disease were more vulnerable to the UHI effect on mental health. The detrimental effects on psychiatric symptoms and white matter microstructure were also observed.
CONCLUSION: The study suggested UHI could be an environmental stressor and induce a heavier burden on mental health. The effective mitigation of urban heat stress could benefit both public health and sustainable development.