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13-10-2011 | Diabetes | Article

Fluctuating HbA1c levels strongly associated with CVD risk in Type 2 diabetes

Abstract

Free abstract

MedWire News: Variability in intrapersonal glycated hemoglobin (HbA1c) levels may be a potent predictor of incident cardiovascular disease (CVD) in patients with Type 2 diabetes, Japanese researchers show.

Although diabetes has long been recognized as a strong risk factor for CV events, it is only recently that the effects of fluctuation in HbA1c, rather than mean HbA1c levels, on incident CV have received attention, they say.

Accordingly, Tetsuya Babazono (Tokyo Women's Medical University) and team examined baseline and follow-up data for 689 patients with Type 2 diabetes who underwent magnetic resonance imaging for screening of silent cerebral infarction.

HbA1c levels were measured over a mean follow-up period of 3.3 years and were used to calculate the intrapersonal standard deviation (SD), mean, and coefficient of variation (CV, the ratio of SD/mean values) of HbA1c for each patient.

HbA1c levels were measured an average of 8.6 times per patient per year.

As reported in the Journal of Diabetes Investigation, 61 CVD events occurred during follow-up.

The 5-year cumulative incidence of CVD in patients in the first, second, third, fourth, and fifth quartiles of SD HBA1c was 4.9%, 8.7%, 17.1%, and 26.2% respectively.

Multivariate Cox regression analysis revealed that patients in the highest quartile of SD HbA1c were at a significantly increased risk for incident CVD compared with those in the lowest quartile, at a hazard ratio (HR) of 3.38.

CV HbA1c was also significantly associated with incident CVD, with those in the highest CV HbA1c quartile being 4.08 times more likely to experience a CVD event than those in the lowest quartile.

Further analysis revealed that patients with both high mean HbA1c and either high SD or high CV HbA1c were at a significantly greater risk for incident CVD compared with those with low SD/CV and low mean HbA1c, at HRs of 3.56 and 5.12, respectively.

"To the best of our knowledge, the present study is the first to demonstrate the association between visit-to-visit variability in HBA1c and incident CVD in patients, as well as in patients who are not Caucasians," say the authors.

"The causal role of fluctuation in HbA1c on the development of CVD needs to be clarified in future studies," they conclude.

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By Sally Robertson