medwireNews: Variability in glycated hemoglobin (HbA1c) levels could have a greater impact on the health of middle-aged people with type 2 diabetes than those who are older, a large Chinese study suggests.
Research in 147,811 Chinese primary care patients revealed that every 1% increase in HbA1c variability increased the likelihood of cardiovascular disease (CVD) or death by 28% in the youngest group, aged 45 to 54 years, compared with an increase of 14% in the oldest group, aged 75 to 84 years, during a median follow-up of 7.4 years.
“Compared to the older group, the detrimental effects of HbA1c variability on the risks of CVD and all-cause mortality in the younger group were higher,” the researchers summarize in Diabetes, Obesity and Metabolism.
“The HbA1c variability may provide additional valuable information as a potential predictor for the development of CVD and all-cause mortality among patients with diabetes. Clinicians should monitor for HbA1c fluctuations in addition to the absolute value.”
Eric Yuk Fai Wan (University of Hong Kong) and colleagues studied electronic health records for people with clinically diagnosed diabetes and no prior CVD at baseline who had at least three HbA1c measurements recorded and attended Hong Kong public primary care clinics between 2008 and 2010.
The mean age of the participants was 64.2 years, and 46% were male. The usual mean HbA1c was 7.5% while variability was 0.8%.
During a median of 1.02 million person–years of follow-up, there were 27,793 incident CVD events and 23,175 all-cause deaths.
After adjusting for patients’ baseline characteristics, there was a positive and log-linear association between HbA1c variability and all outcomes including the primary composite outcome of CVD and all-cause mortality and the individual secondary outcomes of CVD, coronary heart disease, stroke, heart failure, all-cause mortality, CVD mortality, and non-CVD mortality.
The researchers further report a growing trend between incidence rates of all outcomes and increases in HbA1c variability, with the impact of HbA1c variability appearing to increase with diabetes duration.
Each 1% increase in HbA1c variability was associated with a 15% increased likelihood of CVD, a 32% increased likelihood of all-cause death, and a 19% increased likelihood of all events.
And the impact of each 1% increase in HbA1c variability varied according to usual HbA1c at baseline, such that its effect on all outcomes among individuals whose usual HbA1c was less than 7% was approximately eight times greater than among those whose usual HbA1c was at least 8%.
Commenting on the association between HbA1c variability and age, the researchers speculate: “It is possible that older patients were frail and may have experienced weight loss, sarcopenia and high burden [from] other comorbidities, and thus it could unknowingly overshadow the HbA1c variability effect. Younger patients with fewer vascular risk factors may have therefore been more susceptible to HbA1c variability.”
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