HbA1c Across Sex and Age Categories in Type 2 Diabetes: Results from Three Independent Temporal Cohorts Spanning 2012–2024

Background/Objectives: The aim of this study is to describe sex- and age-specific patterns of HbA1c in adults with type 2 diabetes (T2D) mellitus across three temporal cohorts from Southern Italy (2012, 2017, and 2024), and to assess whether glycemic differences between men and women persist, narrow, or evolve over time. Methods: We analyzed three independent cohorts of adults with T2D, including 1249 patients in 2012 and 1125 patients in both 2017 and 2024. HbA1c values were summarized as medians and interquartile ranges within sex- and age-stratified groups. Temporal variation in cohort-specific median HbA1c was examined across timepoints within each sex and age category, and sex differences were assessed within each cohort year. Results: At the population level, median HbA1c values remained within a narrow range across all three cohorts, indicating overall temporal stability of glycemic control. No significant sex differences were observed in 2012 or 2024, and only one age stratum (≥80 years) showed a significant sex difference in 2017, with men exhibiting slightly higher median HbA1c. Age-stratified analyses revealed heterogeneous temporal patterns. In older adults (≥70 years), HbA1c medians were remarkably stable in both sexes (approximately 7.2–7.4% in women and 7.2–7.6% in men). In midlife (40–59 years), women tended to show modest increases or partial reversals in HbA1c, whereas men displayed worsening between 2012 and 2017 followed by stabilization thereafter. The youngest adults (18–29 and 30–39 years) showed the highest HbA1c levels in 2017 and the largest subsequent improvements between 2017 and 2024 in both sexes, with median values decreasing toward approximately 7.1–7.6%. Conclusions: Despite well-described biological and social sex differences in T2D, median HbA1c values in this real-world setting were broadly comparable between men and women and largely stable over a 12-year period. Sex differences were small, inconsistent, and age-dependent, with age, and not sex, emerging as the primary determinant of HbA1c over time. These findings suggest that sex-related disparities in glycemic control may be better understood through a dynamic, life-course perspective rather than static cross-sectional comparisons.