The link between age, sex, fasting plasma glucose and glycated haemoglobin (HbA1c)

Published Date: 01st September 2024

Publication Authors: Green. L

Conference Abstract

Background and aims: We previously reported a sex differential in the distribution of HbA1c for men/women aged less than 50 years vs older individuals, with implications for later diagnosis of type 2 diabetes (T2D) on women's health. Here we further examine the link between glycaemic status with age and sex by examining matched HbA1c and fasting plasma glucose (FPG) levels from two laboratories. Our aim was to explore whether our previous findings of lower HbA1c levels in younger women than younger men related to FPG levels.
Material(s) and Method(s): We extracted data on HbA1c and FPG levels collected on the same patient on the same day from Clinical Biochemistry Laboratory databases from Mersey and West Lancashire Teaching Hospitals NHS Trust (n=10,153) and Cambridge University Hospitals NHS Foundation Trust (n=10,022) between Jan 2019 and Dec 2023. Only cases with a single HbA1c test performed at a GP practice were utilised to minimise the risk of including non-diagnostic tests and tests from specialist care (eg endocrinology, antenatal services), leaving a final dataset of 17,672 patients. We examined the link between HbA1C / FPG levels with age and sex.
Result(s): Confirming our previous data, analysis from both sites showed that mean HbA1c levels were lower in women aged <50 years compared to men aged <50 years, while this sex difference was not observed in those aged >=50 years (Figure upper panel). When median HbA1c levels were plotted by age vs fasting glucose (Figure lower panel), levels in women were 1mmol/mol lower in women than men up until the age of 50 years whereafter they converged for levels of fasting glucose up to 7mmol/L. For women <50 years at the critical diabetes diagnosis threshold 48 mmol/mol, the FPG was 2.6% (Ratio 1.026) higher than in men age<50 years suggesting that women might be diagnosed with actual blood glucose higher (and therefore later than men in relation to glycaemia) whereas for age >=50 years 4.0% (ratio 0.96) actual blood glucose was lower than in men.
Conclusion(s): We here provide additional evidence that there is a differential in the relation between circulating FPG level and HbA1c in younger women vs younger men with implications for the diabetes diagnostic threshold, potentially leading to under diagnosis of type 2 diabetes in younger women and missed opportunities for intervention. These data support our original hypothesis that the lower HbA1c levels in women may reflect the blood loss due to menstruation in younger women, rather than specific age-related changes in glucose homeostasis.

Stedman, M.; Green, L.;Et al. (2024). The link between age, sex, fasting plasma glucose and glycated haemoglobin (HbA1c). Diabetologia. 67(Supp 1), p.S383. [Online]. Available at: https://dx.doi.org/10.1007/s00125-024-06226-0 [Accessed 4 February 2026].