The Association between Cognition and Metabolic Biomarkers among Elder Chinese Population: Findings from the Longitudinal Cohort CHARLS Study

Background: China is one of the countries with the largest burden of cognitive impairment and dementia worldwide, however, studies elucidating potential mechanisms have been relatively scarce in this population. It has been reported that inflammatory or kidney-related metabolic biomarkers are associated with cognitive function and risk for developing dementia among older adults.Objectives: Using the Chinese Health and Retirement Longitudinal Study (CHARLS) database, we aim to investigate the cross-sectional correlations between inflammation or kidney-related metabolic biomarkers and cognitive measure outcomes that were ascertained in the same wave, as well as measures lagged by data collection waves.Methods: After excluding older participants with diagnosed memory problems, we analyzed the association of each blood-based biomarker (e.g. White Blood Cell count, Creatinine, Blood Urea Nitrogen, Uric Acid, Cystatin C, C-Reactive protein) with scores from five cognitive tests (e.g. Immediate Word Recall, Delayed Word Recall, Serial 7’s, Date Naming, Picture Drawing) as well as a total summary recall score. We performed linear regressions for continuous outcomes and logistic regressions for dichotomized outcomes. Covariates such as age, sex, education, smoking, drinking, and residency were also included in multivariate models. We then identified biomarkers that have shown consistent associations across waves.Results: Having elevated CRP (1-3 mg/L) was found to be positively associated with scores from Immediate Word Recall, Delayed Word Recall, Serial 7’s, Date Naming, Picture Drawing. Abnormal levels of Creatinine (Low: <0.74 mg/dl for male and <0.59 mg/dl for female; High:>1.35 mg/dl for male and >1.04 mg/dl for female) were associated with poorer test scores. We did not find consistency in associations between other biomarkers included in this analysis and cognitive test scores.Conclusions: Our study established cross-sectional and longitudinal associations between inflammatory or kidney-related metabolic biomarkers and specific domains of cognition. We also provided biomarker evidence on indicators of kidney function and inflammation for dementia research. Our study results may be used for future intervention exploration by broadening the paradigm in dementia etiology research beyond the amyloid-cascade theory.