Variations in glycated haemoglobin with age among individuals with normal glucose tolerance: Implications for diagnosis and treatment-Results from the ICMR-INDIAB population-based study (INDIAB-12)

Abstract

Aim: To report on glycated haemoglobin (HbA1c) values among individuals with normal glucose tolerance (NGT) at different age groups, using data acquired from a large national survey in India. Materials and methods: Data on glycaemic parameters at different age groups were obtained from the Indian Council of Medical Research-INdia DIABetes (ICMR-INDIAB) study, in adults aged ≥ 20 years representing all parts of India. Age-wise distribution of HbA1c was assessed among individuals with NGT (n = 14,222) confirmed by an oral glucose tolerance test using the World Health Organization (WHO) criteria. Results were validated in another large epidemiological study (n = 1077) conducted in Chennai, India. Results: Among NGT individuals, HbA1c increased gradually with age from 5.16 ± 0.71% (33 mmol/mol) in the age group of 20-29 years to 5.49 ± 0.69% (37 mmol/mol) in those aged 70 + years. In the validation study, conducted in another study population, HbA1c was 5.35 ± 0.43% (35 mmol/mol) in age group of 20-29 years and 5.74 ± 0.50% (39 mmol/mol) in those aged 70 and above. In the INDIAB study, for every decadal increase in age, there is a 0.08% increase in HbA1c and this increase was more significant in females (females: 0.10% vs. males: 0.06%) and in urban (urban: 0.10% vs. rural: 0.08%) population. Conclusions: HbA1c levels increase steadily with age. This suggests that age-specific cutoffs be used while utilizing HbA1c to diagnose diabetes and prediabetes, so as to minimize the risk of overdiagnosis and unnecessary initiation of treatment in elderly people who could have physiological increase in HbA1c levels.