HbA1c levels in the elderly rise but not in precise relationship to glucose tolerance….
In this cross-sectional analysis of adults with known diabetes, impaired glucose tolerance and HbA1c levels increased with age, even after adjusting for covariates including race, BMI, waist circumference, sagittal abdominal diameter, triglyceride/HDL ratio, and fasting and 2-hour plasma glucose levels assessed by an oral glucose tolerance test. The specificity of HbA1c-based prediabetes diagnosis decreased substantially as age increased.
"For the same level of blood glucose, HbA1c is higher in the elderly, suggesting a decreased specificity for the diagnosis of diabetes with increasing age. Given that glucose levels may be normal, basing a diagnosis on HbA1c will result in more risk for hypoglycemia with treatment; on the other hand, one wonders whether the higher HbA1c reflects decreased clearance that may also apply to tissues damaged by glucose, rendering them more susceptible to damage in the presence of ‘normal’ glucose levels," said the researchers.
Examining the measures of sensitivity, specificity, and negative and positive predictive value based on HbA1c criteria using the OGTT as gold standard, the researchers found a remarkable decrement in performance, predominantly sensitivity, with age. This is an issue superimposed on the well-recognized problem that the sensitivity of HbA1c for diagnosis of diabetes compared with OGTT is quite limited, clustering in most populations around 50%.
Researchers concluded that in two large datasets, using different methods to measure HbA1c, the association of age with higher HbA1c levels was consistent and similar; was both statistically and clinically significant; was unexplained by features of aging; and reduced diagnostic specificity. Age should be taken into consideration when using HbA1c for the diagnosis and management of diabetes and prediabetes.
- The association of age with higher HbA1c levels was consistent
- HbA1c level is rising not simply in precise relationship to glucose tolerance
- Age should be taken into consideration when using HbA1c for the diagnosis and management of diabetes and prediabetes
Diabet. Med. 2014 Aug 01;31(8)927–935, N Dubowitz, W Xue, Q Long, JG Ownby, DE Olson, D Barb, MK Rhee, AV Mohan, PI Watson-Williams, SL Jackson, AM Tomolo, TM Johnson, LS Phillips