Renal function, Alzheimer’s plasma biomarker, and cognitive phenotypes among rural older adults in China: a population‐based study

Abstract

AbstractBackgroundEmerging evidence has linked impaired renal function with dementia, but the neuropathological mechanisms underlying the association remains poorly understood. We sought to examine the relationships of renal function, Alzheimer’s plasma biomarker, and cognitive phenotypes among rural Chinese older adults.MethodThis population‐based cross‐sectional study included 5715 participants (age ≥60 years; 57.15% women; 40.49% illiteracy) in the Multimodal Interventions to Delay Dementia and Disability in Rural China (MIND‐China). We calculated the estimate glomerular filtration rate (eGFR) using serum creatinine and the simplified modification of diet in renal disease equation specifically for individuals from China, and impaired renal function was defined as eGFR <60 mL/min/1.73 m2. Dementia, Alzheimer’s disease (AD), and vascular dementia (VaD) were diagnosed following the international criteria. Plasma amyloid‐β (Aβ) 40, Aβ42, total tau, and neurofilament light chain (NfL) concentrations were measured using the SIMOA platform in a subsample (n = 1446). Data were analyzed using logistic, the general linear regression, and mediation models.ResultOf the 5715 participants, 283 (4.95%) were detected with renal function impairment, and 326 (5.70%) were diagnosed with dementia (195 with AD and 10 with VaD). The multivariable‐adjusted odds ratios of eGFR <60 mL/min/1.73 m2 (vs. >90mL/min/1.73 m2) were 2.43 (95% confidence interval [CI] 1.56‐3.72) for all‐cause dementia, 2.74 (1.64‐4.49) for AD, and 1.30 (0.50‐2.98) for VaD. In the plasma biomarkers subsample, controlling for demographic factors, impaired renal function was significantly associated with higher levels of plasma Aβ40 (demographic‐adjusted β‐coefficient = 59.06; 95%CI 46.93‐71.19), Aβ42 (3.41; 2.62‐4.20), NfL (14.57; 9.08‐20.05), and total tau (0.74; 0.48‐1.01), and the observed associations remained significant even in the multivariable‐adjusted model (P<0.001). The mediation analysis showed that total tau mediated 12.77% of the association between impaired renal function and AD.ConclusionImpaired renal function is associated with an increased risk of dementia and AD. Plasma total tau may partly underlie the association of renal function with Alzheimer’s dementia.