Anemia status transitions, cumulative hemoglobin exposure, and component-specific associations with sarcopenia

Sarcopenia and anemia co-occur frequently among middle-aged and older adults, yet the relationship between anemia status transitions and sarcopenia remains poorly characterized. Drawing on data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted an analysis of 2,507 participants aged 45 years and older who were free of sarcopenia at baseline. Anemia was defined according to World Health Organization criteria as hemoglobin levels < 13 g/dL for men and < 12 g/dL for women. Anemia status transitions between 2011 and 2015 were classified as persistent non-anemia, incident anemia, resolved anemia, and persistent anemia. Sarcopenia and its components were ascertained in 2015 according to the Asian Working Group for Sarcopenia 2019 criteria. Multivariable logistic regression, restricted cubic spline analysis, subgroup analyses, and multiple sensitivity analyses were performed. Persistent anemia was significantly associated with higher odds of sarcopenia compared with persistent non-anemia (OR = 1.85, 95% CI: 1.06–3.24). Associations were most evident for low muscle mass, particularly among participants with resolved anemia (OR = 1.57, 95% CI: 1.00-2.47) and persistent anemia (OR = 1.73, 95% CI: 1.09–2.75). Cumulative hemoglobin exposure demonstrated a significant inverse dose-response relationship with both low muscle mass and sarcopenia, with each standard deviation increment associated with 17% and 21% lower odds, respectively. Anemia status transitions and cumulative hemoglobin exposure were associated with sarcopenia-related outcomes among middle-aged and older Chinese adults, with associations concentrated in the muscle mass domain.