Association between hemoglobin within the normal range and hemoglobin A1c among Chinese non-diabetes adults

BACKGROUND: Hemoglobin A1c (HbA1c) is the product of a non-enzymatic chemical reaction between hemoglobin (Hb) and glucose. However, the association between Hb and HbA1c remains to be fully elucidated in view of the controversial findings reported to date. Therefore, our aim in this study was to evaluate the association between Hb levels within the normal range and HbA1c levels among Chinese non-diabetes adults using cross-sectional data from the China Health and Nutrition Survey 2009. METHODS: Our analysis was based on the data of 1659 non-diabete adults 20–49 years of age. Multivariable linear models were applied to examine the association between Hb and HbA1c levels. Subgroup analyses stratified by age and sex were also performed. RESULTS: The association between Hb and HbA1c levels was positive in the unadjusted model (β =0.020, 95% CI: 0.008, 0.032). However, this association did not remain significant when the regression model was minimally adjusted for age and sex (β =0.006, 95% CI: − 0.014, 0.024); this association became negative when the model was further adjusted for covariates whose effect estimates of HbA1c levels more than 10% (β = − 0.042, 95% CI: − 0.064, − 0.020). The association remained negative on subgroup analyses stratified by age (20–34 years: β = − 0.052, 95% CI: − 0.091, − 0.013; 35–49 years: β = − 0.041, 95% CI: − 0.068, − 0.014) and sex (men: β = − 0.042, 95% CI: − 0.074, − 0.010; women: β = − 0.042, 95% CI: − 0.073, − 0.012) when controlling for covariates. CONCLUSIONS: Our findings revealed that Hb levels within the normal range were negatively associated with HbA1c levels among Chinese non-diabetes adults. Confounding factors, such as red blood cell counts can affect the association between Hb and HbA1c levels. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-021-00704-x.