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

Objective: Target HbA_1c values given in the most National Therapeutic Guidelines for patients with diabetes and cut-off HbA_1c values for diabetes diagnosis are usually not taking the age of the respective patients into account; despite the fact that an increase in HbA_1c in subjects without diabetes with age is known for some time. In order to further quantify the association between age and HbA_1c 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 HbA_1c 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 HbA_1c 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. HbA_1c measurements were DCCT adjusted. Results: Patients with age>70 years have a 0.47% [5.14 mmol/mol] higher HbA_1c compared to those<30 years. The mean HbA_1c 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 HbA_1c per decade. Conclusion: HbA_1c 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.