Visceral fat area and red-blood-cell-related indices in adults with type 2 diabetes: Cross-sectional evidence of nonlinear associations

Abstract

BACKGROUND

Visceral adiposity is common in type 2 diabetes (T2D) and is linked to cardiometabolic risk. Complete blood counts are routinely measured, but their relationship with visceral fat in T2D is not well described.

AIM

To evaluate the association between visceral fat area (VFA) and red blood cell (RBC)-related indices in Chinese adults with T2D, and to explore potential nonlinear relationships and threshold effects across different patient subgroups.

METHODS

We conducted a cross-sectional study among adults with T2D at the Metabolic Management Center of Quzhou People’s Hospital. A formal sample size calculation was performed to ensure sufficient statistical power. VFA was measured by multifrequency bioelectrical impedance analysis. We examined RBC count, hemoglobin (HGB), hematocrit (HCT) and other blood cell indices. To address potential selection bias and maximize statistical power, multiple imputation by chained equations was used to handle missing glycated HGB (HbA1c) data (n = 1180). We fitted multivariable linear regression models with each hematological index as the outcome and VFA as the exposure. We used generalized additive models and two-piecewise linear regression to assess nonlinearity and threshold effects, where nonlinearity refers to associations that deviate from a straight line, such as those exhibiting plateau or threshold patterns. We also performed prespecified subgroup analyses by age, sex, body mass index (BMI) and HbA1c. Sensitivity analyses were conducted to compare the results between the complete-case (n = 590) and the imputed datasets to ensure the robustness of the findings.

RESULTS

We included 1180 adults with T2D. In fully adjusted models, using multiple imputation to account for missing glycemic data, higher VFA was independently associated with higher HCT, HGB, and RBC and white blood cell (WBC) counts. Smoothing curves revealed nonlinear patterns for HCT, HGB and RBCs: The increases were steeper at lower VFA levels and reached a plateau at higher levels. In threshold models, the inflection point was approximately 45 cm² for HCT, HGB and RBCs (all P < 0.001 for the nonlinear trend). Subgroup analyses showed that these associations were more robust in men and in participants with BMI < 28 kg/m². Sensitivity analyses confirmed that the results were consistent across HbA1c categories, and the inclusion of imputed data significantly enhanced the statistical power for the association between VFA and WBC count.

CONCLUSION

In adults with T2D, greater visceral adiposity was independently and robustly associated with higher HCT, HGB, and RBC and WBC counts, with the relationships appearing nonlinear and characterized by a threshold effect. These findings, which remained consistent after addressing missing data through multiple imputation, suggest that routine hematological indices are sensitive indicators of visceral fat burden, particularly in specific clinical subgroups. Longitudinal studies are needed to clarify the temporal sequence and the potential clinical utility of integrating these indices into metabolic risk stratification.

Keywords: Type 2 diabetes; Visceral fat area; Hematocrit; Hemoglobin; Red blood cell count; Non-linear association; Cross-sectional study

Core Tip: This study revealed a nonlinear relationship between visceral fat area (VFA) and red blood cell-related indices, specifically hematocrit, hemoglobin and red blood cell count, in adults with type 2 diabetes (T2D). The association was more pronounced at lower VFA levels (inflection point approximately 45 cm²) and in nonobese individuals. These findings suggest that routine hematological markers serve as accessible indicators of visceral adiposity burden. This emphasizes the importance of integrated metabolic and hematological monitoring to better assess cardiometabolic risk in T2D management.