Psychiatric Disorders Mediate the Association between Floods and Dementia: A Prospective Cohort Study in the UK Biobank

Yao Wu; Bo Wen; Danijela Gasevic; Rongbin Xu; Zhengyu Yang; Pei Yu; Yanming Liu; Guowei Zhou; Yan Zhang; Jiangning Song; Hong Liu; Shanshan Li; Yuming Guo

doi:10.1021/envhealth.4c00241

Psychiatric Disorders Mediate the Association between Floods and Dementia: A Prospective Cohort Study in the UK Biobank

Environ Health (Wash). 2025 Mar 13;3(6):680-689. doi: 10.1021/envhealth.4c00241. eCollection 2025 Jun 20.

Authors

Yao Wu¹, Bo Wen¹, Danijela Gasevic^{1

2}, Rongbin Xu¹, Zhengyu Yang¹, Pei Yu¹, Yanming Liu¹, Guowei Zhou³, Yan Zhang³, Jiangning Song⁴, Hong Liu³, Shanshan Li¹, Yuming Guo¹

Affiliations

¹ Climate, Air Quality Research Unit, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC 3004, Australia.
² Centre for Global Health, Usher Institute, The University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, United Kingdom.
³ Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
⁴ Monash Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC 3800, Australia.

Abstract

Flooding has become more frequent and severe worldwide, leading to an increased burden of psychiatric disorders (e.g., depression and anxiety). Psychiatric disorders are associated with an increased risk of subsequent dementia. However, the associations among floods, psychiatric disorders, and dementia are still unclear. Using a population cohort from the UK Biobank, we aimed to investigate the mediating role of psychiatric disorders on the associations between floods and dementia. In this study, cumulative exposure to floods over an eight-year period preceding the study baseline was assessed for each participant at residential addresses. Multivariable Cox proportional hazards regression was used to study the associations of flooding exposure with psychiatric disorders and dementia. Stratified analyses and mediation analyses were conducted to examine whether psychiatric disorders mediate the relationship between floods and dementia. During a median follow-up of 12.3 years (interquartile range: 11.6-13.0), 0.9% (2,028) of participants developed dementia and 9.5% (21,629) were diagnosed with psychiatric disorders. The flooding exposure was associated with an 8.0% increased risk of incident dementia (Hazard Ratio [HR]: 1.080, 95% CI: 1.023-1.141). The flood-dementia association was observed to be partially mediated by several subtypes of psychiatric disorders (overall proportion of mediation: 75.7%), with psychotic disorder accounting for 49.7% (indirect effect HR: 1.039, 95% confidence interval: 1.015-1.064) of flood-related dementia, followed by stress-related disorder (proportion of mediation: 18.1%), and depression (proportion of mediation: 3.9%). This study provides evidence of an increased risk of dementia associated with exposure to floods, with psychiatric disorders playing a crucial mediating role in the flood-related dementia pathway. These findings suggest that flooding exposure is a critical risk factor for dementia, and targeted interventions addressing postdisaster mental health may be crucial for dementia prevention in affected populations.

Keywords: dementia; depression; flood; psychiatric disorders; stress.