https://diabetes.acponline.org/archives/2016/08/12/1.htm

HbA1c variability linked to risk of adverse long-term outcomes in type 2 diabetes

The effect of HbA1c variability on outcomes, including mortality, myocardial infarction, and stroke, appeared to be independent of directional trends or baseline HbA1c level.


Variability in HbA1c levels may be linked to higher risk for adverse long-term outcomes in patients with type 2 diabetes, according to a recent study.

Researchers performed a retrospective cohort study using Veterans Affairs and Medicare claims to examine whether HbA1c variability over a 3-year baseline period had an independent effect on mortality, hospitalization for ambulatory care-sensitive conditions, and myocardial infarction or stroke. HbA1c variability was categorized as quartiles and defined as SD, coefficient of variation, and adjusted SD. Quartile 1 served as the reference quartile, while quartiles 3 and 4 were quartiles with the most HbA1c variability. The study results were published online on July 17 by Diabetic Medicine.

A total of 50,861 veterans with type 2 diabetes were included in the study. All were required to have an existing metformin prescription followed by a second diabetes medication. The mean patient age was 66 years; 98% were men, and 86% were white. During a mean of 3.3 years of follow-up, all measures of HbA1c variability significantly predicted each of the study outcomes. When the adjusted SD measure was used, hazard ratios for mortality were 1.14 (95% CI, 1.04 to 1.05) for the third HbA1c quartile and 1.42 (95% CI, 1.28 to 1.58) for the fourth HbA1c quartile. For myocardial infarction or stroke, hazard ratios for the third and fourth quartile were 1.25 (95% CI, 1.10 to 1.41) and 1.23 (95% CI, 1.07 to 1.42), respectively, while for ambulatory care-sensitive conditions they were 1.10 (95% CI, 1.03 to 1.18) and 1.11 (95% CI, 1.03 to 1.20), respectively. The effect of HbA1c variability on outcomes appeared to be independent of directional trends or baseline HbA1c level. Higher levels of HbA1c at baseline were also independently predictive of each outcome, with levels above 7% significantly increasing odds of hospitalization for ambulatory care-sensitive conditions and myocardial infarction or stroke and levels of 9% or higher significantly increasing odds of mortality.

The authors noted that their results may not be generalizable, that they could not confirm the causality of the relationship between HbA1c variability and outcome, and that no information was available on diabetes duration. However, they concluded that patients with type 2 diabetes whose HbA1c levels vary are at higher risk for certain adverse outcomes as well as death. “Limiting the range of [HbA1c] fluctuations over time and adhering to guideline-directed [HbA1c] target levels may reduce the risk of diabetes complications,” the authors wrote.