HbA1c and Age in Non-Diabetic Subjects: An Ignored Association?

Objective: Target HbA1c values given in the most National Therapeutic Guidelines for patients with diabetes and cut-off HbA1c values for diabetes diagnosis are usually not taking the age of the respective patients into account; despite the fact that an increase in HbA1c in subjects without diabetes with age is known for some time. In order to further quantify the association between age and HbA1c in non-diabetic subjects an analysis of one German register was performed.
Methods: In this cross-sectional study we analyzed data from 7 699 visits of 2 921 patients without diabetes (age 46.6 y [range 18-93 y]; 69.1% women; BMI 27.6±6.4 kg/m²) who had at least one HbA1c and blood glucose measurement. Data were drawn from an electronic patient record system (EMIL™) in which data were collected between 01/1992 and 01/2014. The patients were divided in 6 age groups (< 30 years [n=1 057];>30-40 years [n=1 160];>40-50 years [n=1 693];>50-60 years [n=1 523];>60-70 years [n=1 310];>70 years [n=956]) and the HbA1c values of these groups were compared. Patients with: gestational diabetes, use of systemic glucocorticoids, malignant neoplasm, age<18 y at time of first visit and IGT were excluded. HbA1c measurements were DCCT adjusted.
Results: Patients with age>70 years have a 0.47% [5.14 mmol/mol] higher HbA1c compared to those<30 years. The mean HbA1c of the age groups was:<30 4.98% [30.96 mmol/mol],>30-40 5.07% [31.99 mmol/mol],>40-50 5.17% [33.10 mmol/mol],>50-60 5.33% [34.79 mmol/mol],>60-70 5.42% [35.79 mmol/mol] and>70 years 5.45% [36.10 mmol/mol]. In a multiple linear model the regression coefficient for each year of age increase was β=0.0074 (p<0.001); thus age results in an increase of 0.074% in HbA1c per decade.
Conclusion: HbA1c increases significantly with ageing in people without diabetes. The use of different cut-off values for every age range for diagnosis of diabetes should be discussed. © Georg Thieme Verlag KG Stuttgart · New York.