Anemia and Kidney Function Decline among the Middle-Aged and Elderly in China: A Population-Based National Longitudinal Study

Abstract

Chronic kidney disease (CKD) is a public health burden, and anemia is common among patients with CKD. However, less is known regarding the longitudinal association between anemia and deterioration of kidney function among the general population. The China Health and Retirement Longitudinal Study is a nationally representative survey for households with members $\text{aged}\ge 45$ years. Participants without creatinine and demographic data in 2011 and 2015 were excluded. Anemia was defined according to definitions of the World Health Organization. Rapid decline in kidney function was defined as a ≥16.9% (quartile 3) decline in estimated glomerular filtration rate (eGFR), calculated using the CKD-EPI equation during 2011-2015. Multivariate logistic regression and restricted cubic splines were used to explore their relationship. Altogether, 7210 eligible participants were included in the analysis, with a mean age of $58.6\pm 8.8$ years. Rapid decline in kidney function occurred among 1802 (25.0%) participants. Those with kidney function decline were more likely to be older, male, and have anemia, lower eGFRs, hypertension, and cardiovascular disease ( $P<0.05$ ). Anemia, or hemoglobin, was independently associated with rapid decline in kidney function after adjusting for potential confounding factors ( $\text{OR}=1.64$ , 95% CI, 1.32-2.04; $\text{OR}=0.90$ , 95% CI, 0.87-0.94, respectively). Restricted cubic splines showed a nonlinear relationship between hemoglobin and rapid decline in kidney function, especially for men with anemia ( $P<0.05$ ). In conclusion, anemia is an independent risk factor for progression of kidney function among the middle-aged and elderly population. Attentive management and intervention strategies targeting anemia could be effective to reduce the risk of kidney failure and improve the prognosis of the general population.