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

A Population-Based Correlation Analysis Between Hemoglobin A1c and Hemoglobin Levels

BACKGROUND

Glycated hemoglobin (HbA1c) is widely used to assess long-term glycemic control in individuals with diabetes. However, various conditions that affect hemoglobin levels or the lifespan of red blood cells can compromise the accuracy of HbA1c measurements. Despite extensive research, the relationship between HbA1c and hemoglobin remains unclear. This study aims to clarify this relationship by examining its correlation across diverse age and gender cohorts.

METHODS

Data from 217,991 participants aged 20 to 69 years were collected from health examination centers in Southwest China. Standardized methodologies were used to measure HbA1c and hemoglobin levels. Generalized additive models (GAM) were utilized to analyze non-linear relationships and adjust for potential confounding variables. Gender-specific reference intervals (RIs) for hemoglobin were also established.

RESULTS

A gender-specific association was observed between HbA1c and hemoglobin levels. In men, HbA1c levels decreased with increasing hemoglobin. Among women, a negative correlation was observed in premenopausal women (aged ≤ 45 years), whereas postmenopausal women (aged > 45 years) showed a positive correlation, with HbA1c levels increasing as hemoglobin levels rose. Additionally, HbA1c levels increased with age in both genders, with a more pronounced rise in women after the age of 45.

CONCLUSION

This study highlights significant gender- and age-related differences in the relationship between HbA1c and hemoglobin. The findings suggest that estrogen-related metabolic changes may influence HbA1c levels, with potential implications for diabetes management and hormone therapy in postmenopausal women.

Hemoglobin within normal range is negatively related to hemoglobin A1c in a nondiabetic American population aged 16 years and older

BACKGROUND

Protein glycosylated hemoglobin, hemoglobin A1c (HbA1c) binds hemoglobin (Hb) in red blood cells to blood glucose. However, the relationship between Hb and HbA1c remains unclear.

AIM

To elucidate their relationship in a nondiabetic population aged ≥ 16 years in the United States, using data from the 1999-2018 National Health and Nutrition Examination Survey.

METHODS

This study was based on data from 44560 adults aged ≥ 16 years, excluding those with diabetes. The relationship was estimated using a multivariate regression. We also used piecewise linear regression for subgroup analysis based on age and sex stratification and analysis of the threshold effects of Hb on HbA1c.

RESULTS

Hb and HbA1c levels were negatively correlated in the unadjusted model (β = -0.01; 95%CI: -0.01, -0.01). The correlation was significantly negative when the regression model was minimally regulated and stratified by age and sex, and remained negative when the model was further regulated (more than 10%) to identify covariates with the HbA1c level influence estimates. In subgroup analyses based on age and sex stratification, the association remained negative when the covariates were controlled. A nonlinear relationship was observed between them when the Hb levels reached the tipping point (13.2 g/dL) (adjusted odds ratio, -0.04; 95%CI: -0.05, -0.03) and when the Hb levels exceeded 13.2 g/dL (adjusted odds ratio, -0.10; 95%CI: -0.10, -0.09).

CONCLUSION

Our study shows that normal Hb levels are negatively correlated with HbA1c in nondiabetic Americans aged ≥ 16 years.

Prognostic Significance of HbA1c Level in Asian Patients with Prediabetes and Coronary Artery Disease

Background: Measuring glycosylated hemoglobin (HbA1c) is a simple way to assess patients with prediabetes ordiabetes mellitus. It has been shown that HbA1c level predicts prognosis in patients with coronary artery disease (CAD)and the incidence of diabetes mellitus. However, the prognostic significance of HbA1c level in Asian patients withprediabetes and CAD is not yet clear. Our study aimed to determine the relationship between HbA1c level and majoradverse cardiovascular events (MACE) in patients with prediabetes and CAD.Methods: We enrolled 1367 patients with prediabetes and CAD in the final analysis, and grouped them according tothe HbA1c level. Primary end points included nonfatal myocardial infarction, hospitalization for unstable angina, andischemia-driven revascularization. Cox proportional-hazards regression analysis was used to determine the relationshipbetween HbA1c level and MACE after our accounting for confounding factors.Results: A total of 1367 patients (age 58.8 ± 10.3 years; 71.6% men) were included. During 43 months of follow-up,197 patients experienced at least one primary end point event. Multivariate Cox proportional-hazards regression analysisshowed in comparison of HbA1c levels that the hazard ratio for primary end points was 4.110, with a 95% confidence interval of 2.097–6.011 (P < 0.001).Conclusions: HbA1c level positively correlated with MACE, demonstrating it is a valuable indicator for independentlypredicting MACE in Asian patients with prediabetes and CAD.