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09-04-2020 | Glycemic control | News

High usual HbA1c raises cardiovascular risk in type 2 diabetes

Sara Freeman

medwireNews: The risk for someone with type 2 diabetes experiencing a cardiovascular disease (CVD) event increases by 21% for every 1% increase in their usual glycated hemoglobin level (HbA1c) above 7.0% (53 mmol/mol), study findings suggest.

Furthermore, their risk for death from such a CVD event is increased by 37%, the researchers report in Diabetes, Obesity and Metabolism.

“There have been four major trials [UKPDS, ACCORD, ADVANCE, and VADT] investigating blood glucose control on the risks of CVD and mortality,” acknowledge Eric Wan (The University of Hong Kong, China) and colleagues. However, they note that these have “produced contradictory findings.”

Wan et al performed a retrospective cohort study to take a further look at the effect of people’s usual HbA1c levels on their 10-year CVD risk. To do this they looked at the primary care electronic medical records of 174,028 individuals aged between 45 and 84 years who had a recorded diagnosis of type 2 diabetes, no prior history of CVD, and the results of at least one HbA1c measurement available 2 years before the baseline of 2008–2010.

After a median follow-up of 8.4 years, there were 34,072 recorded CVD events and 3719 deaths due to CVD. The usual average HbA1c level of the entire study population was calculated as 7.5% (58 mmol/mol).

A higher number of CVD events was found when comparing the highest with the lowest quintiles of usual HbA1c.

Crude cumulative incidence rates per 1000 person–years were: 25.8 for an HbA1c of below 6.7% (49.2 mmol/mol); 26.1 for an HbA1c of 6.7–7.2% (49.2–54.9 mmol/mol); 26.8 for an HbA1c of 7.3–7.7% (55.0–60.7 mmol/mol); 27.6 for an HbA1c of 7.8–8.4% (60.8–68.0 mmol/mol); and 29.8 for an HbA1c of more than 8.4% (68.1 mmol/mol).

The corresponding crude cumulative incidence rates for stroke were 12.2, 11.9, 12.7, 12.7, and 13.5 per 1000 person–years, for heart failure were 6.7, 6.6, 6.5, 7.4, and 8.8 per 1000 person–years, and for CVD mortality were 2.5, 2.6, 2.6, 2.7, and 3.2 per 1000 person–years.

After adjustment, a “[c]urvilinear association was found between the usual HbA1c and total CVD, stroke, heart failure and CVD mortality risk,” Wan and team note.

While a usual HbA1c of below 7.0% was not associated with the CVD outcomes, values above this showed positive associations, the researchers report. Adjusted hazard ratios per 1% increase in usual HbA1c above this threshold were 1.21 for any CVD event, 1.18 for stroke, 1.46 for heart failure, and 1.37 for death due to CVD.

“The usual HbA1c effect on patients with younger age was stronger compared to those with older age,” the researchers observe.

This “suggested that low usual HbA1c level did not necessarily provide additional protective effect over CVD risks,” they add.

“Therefore, patient-centered targets might optimize clinical benefits for individual patients.”

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2020 Springer Healthcare Ltd, part of the Springer Nature Group

Diabetes Obes Metab 2020; doi:10.1111/dom.14157