Association of four insulin resistance surrogates with anemia among middle-aged and elderly individuals: a cross-sectional study from the China Health and Retirement Longitudinal Study.

BACKGROUND

Anemia is a prevalent global public health challenge. The aim of this study was to investigate the cross-sectional association between insulin resistance (IR) surrogates (TyG index, TG/HDL-C ratio, METS-IR, and eGDR) and anemia in middle-aged and elderly Chinese individuals.

METHODS

Data from the China Health and Retirement Longitudinal Study (CHARLS) wave 3 (2015) were analyzed. A total of 10,402 participants aged 45 years or older were included. Multiple logistic regression models and restricted cubic spline (RCS) analyses were employed to examine the associations, applying sampling weights to ensure national representativeness. Collinearity diagnostics were performed to validate model stability.

RESULTS

In this cross-sectional study, 3,590 (34.5%) participants had anemia. After adjusting for confounders (including age, gender, socioeconomic status, lifestyle, and comorbidities), the TyG index, TG/HDL-C ratio, and METS-IR were inversely associated with anemia odds. For each unit increase in TyG, TG/HDL-C, and METS-IR, the odds of anemia decreased by 44% (OR = 0.56, 95% CI = 0.52-0.61), 10% (OR = 0.90, 95% CI = 0.88-0.92), and 5% (OR = 0.95, 95% CI = 0.93-0.96), respectively. Conversely, elevated eGDR levels (indicating lower insulin resistance) were associated with higher odds of anemia (OR = 1.28, 95% CI = 1.22-1.35 per unit increment, adjusted model without mathematical coupling). Non-linear dose-response relationships were observed for all four surrogates. Significant interactions were found between IR surrogates and demographics (age, gender) and lifestyle factors (smoking, BMI).

CONCLUSION

Higher levels of TyG, TG/HDL-C, and METS-IR are associated with lower prevalence of anemia, whereas higher eGDR is associated with higher anemia prevalence in middle-aged and elderly Chinese adults. These findings highlight complex metabolic-hematologic interactions, though the cross-sectional design precludes causal inference. Further longitudinal research is warranted to elucidate the underlying mechanisms.