Depression as a Mediator of the Association Between Wealth Status and Risk of Cognitive Impairment and Dementia: A Longitudinal Population-Based Cohort Study

Article type: Research Article

Authors: Zhou, Rui^{a; 1} | Liu, Hua-Min^{a; 1} | Li, Fu-Rong^a | Yang, Hai-Lian^a | Zheng, Jia-Zhen^a | Zou, Meng-Chen^b | Zou, Lian-Wu^c | Wu, Xiao-Xiang^{d; *} | Wu, Xian-Bo^{a; *}

Affiliations: [a] Department of Epidemiology, School of Public Health, Southern Medical University (Guangdong Provincial Key Laboratory of Tropical Disease Research), Guangzhou, Guangdong, China | [b] Department of Endocrinology and Metabolism, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China | [c] Department of Psychiatry, Baiyun Jingkang Hospital, Guangzhou, Guangdong, China | [d] Department of General Surgery, People’s Liberation Army General Hospital of Southern Theatre Command, Guangzhou, Guangdong, China

Correspondence: [*] Correspondence to: Xiao-Xiang Wu, PhD, Department of General Surgery, General Hospital of Southern Theatre Command, No. 111, Liuhua Road, Yuexiu District, 510016 Guangzhou, Guangdong, China. Tel.: (+86) 13660569824; E-mail: 786486617@qq.com and Xian-Bo Wu, PhD, Department of Epidemiology, School of Public Health, Southern Medical University (Guangdong Provincial Key Laboratory of Tropical Disease Research), No. 1063-No. 1023, Shatai South Road, Baiyun District, 510515 Guangzhou, China. Tel.: (+20) 61648311; Fax: (+20) 61648312; E-mail: wuxb1010@smu.edu.cn.

Note: [1] These authors contributed equally to this work.

Abstract: Background:Wealth and income are potential modifiable risk factors for dementia, but whether wealth status, which is composed of a combination of debt and poverty, and assessed by wealth and income, is associated with cognitive impairment among elderly adults remains unknown. Objective:To examine the associations of different combinations of debt and poverty with the incidence of dementia and cognitive impairment without dementia (CIND) and to evaluate the mediating role of depression in these relationships. Methods:We included 15,565 participants aged 51 years or older from the Health and Retirement Study (1992–2012) who were free of CIND and dementia at baseline. Dementia and CIND were assessed using either the modified Telephone Interview for Cognitive Status (mTICS) or a proxy assessment. Cox models with time-dependent covariates and mediation analysis were used. Results:During a median of 14.4 years of follow-up, 4,484 participants experienced CIND and 1,774 were diagnosed with dementia. Both debt and poverty were independently associated with increased dementia and CIND risks, and the risks were augmented when both debt and poverty were present together (the hazard ratios [95% confidence intervals] were 1.35 [1.08–1.70] and 1.96 [1.48–2.60] for CIND and dementia, respectively). The associations between different wealth statuses and cognition were partially (mediation ratio range: 11.8–29.7%) mediated by depression. Conclusion:Debt and poverty were associated with an increased risk of dementia and CIND, and these associations were partially mediated by depression. Alleviating poverty and debt may be effective for improving mental health and therefore curbing the risk of cognitive impairment and dementia.

Keywords: Cognitive impairment, cohort studies, dementia, depression, mediation analysis, wealth status

DOI: 10.3233/JAD-201239

Journal: Journal of Alzheimer's Disease, vol. 80, no. 4, pp. 1591-1601, 2021