Socioeconomic Status and Risks of Cognitive Impairment and Dementia: A Systematic Review and Meta-Analysis of 39 Prospective Studies.

BACKGROUND: In recent decades, increased attention has been paid to the impact of socioeconomic status (SES) on cognition function and dementia, however, an ongoing debate continues to exist. The objective of our study was to explore the potential effect of SES on the risks of cognitive dysfunction and dementia. METHODS: PubMed, Cochrane Library, and EMBASE were searched for prospective studies from inception to 9 January 2022. Meta-analyses using random-effect models were performed, and then subgroup analyses stratified by study characteristics for specific outcomes were conducted. RESULTS: Thirty-nine prospective studies (1,485,702 individuals) were eligible for inclusion, of which 25 reported the incidence of dementia and 14 reported cognitive decline. Primary results of the meta-analyses found an elevated combined risk of cognitive impairment and dementia (relative risk [RR] = 1.31, 95% confidence interval [CI] = 1.16-1.49) in low-SES participants compared with high-SES participants. We also found an elevated risk of all-cause dementia (RR = 1.40, 95% CI = 1.12-1.74) in low-SES participants. Further subgroup analyses stratified by education, occupation, and income showed that low education subgroup (RR = 1.21, 95% CI = 1.04-1.41) and low-income subgroup (RR = 1.22, 95% CI = 1.10-1.35) had an increased combined risks of cognitive impairment and dementia, but only individuals with lower education had a higher risk of dementia (RR = 1.66, 95% CI = 1.20-2.32). CONCLUSIONS: Low SES substantially increased the risk of dementia and cognitive dysfunction, suggesting that public health strategies could reduce the dementia burden by reducing social inequalities.

Tau Pathologies Mediate the Associations of Vascular Risk Burden with Cognitive Impairments in Non-demented Elders: The CABLE Study.

BACKGROUND: Studies suggested that vascular dysfunction might increase the risk of developing Alzheimer's disease (AD), but the underlying mechanisms still remain obscure. OBJECTIVE: To evaluate the associations of vascular risk burden with AD core pathologies and investigate the effects of AD core pathologies on relationships between vascular risk burden and cognitive impairments. DESIGN: The Chinese Alzheimer's Biomarker and LifestyLE (CABLE) study was principally focusing on aging, as well as the risk factors and biomarkers of AD initiated in 2017. SETTING: The CABLE study was a large cohort study established in Qingdao, China. PARTICIPANTS: A total of 618 non-demented elders were obtained from CABLE study. MEASUREMENTS: The general vascular risk burden was assessed by the Framingham General Cardiovascular Risk Score (FGCRS). Multivariate linear regression analyses were performed to evaluate the associations of FGCRS with cerebrospinal fluid (CSF) AD biomarkers and cognition. Casual mediation analyses were performed to investigate the mediating effects of AD biomarkers on cognition. RESULTS: Increased FGCRS was related to higher levels of CSF total tau (t-tau, p < 0.001), phosphorylated tau (p-tau, p < 0.001) as well as the ratio of t-tau and amyloid-ß 42 (t-tau/Aß42, p = 0.010), and lower Chinese-Modified Mini-Mental State Examination (CM-MMSE, p = 0.010) score. Stratified analysis indicated that age modified the associations, with FGCRS being significantly associated with tau pathology (p < 0.001 for t-tau and p-tau) in middle-aged group (<65 years old), instead of older group. The influences of FGCRS on cognitive impairments were partially mediated by tau pathologies (a maximum proportion of 20.9%). CONCLUSIONS: Tau pathology might be a pivotal mediator for effects of vascular risk on cognitive decline. Early and comprehensive intervention for vascular risk factors might be a potential approach to delaying or preventing cognitive impairment and AD.