10-year Study: Usual A1c >7% Raises Cardiovascular Risk in Type 2 Diabetes

September 8, 2020
Grace Halsey
Grace Halsey

The risk of having a CVD-related event is increased by 21% for every 1% increase in usual A1c >7% in patients with type 2 diabetes, a new study finds.

Among patients with type 2 diabetes (T2D), the risk of experiencing a cardiovascular disease (CVD) event is increased by 21% for every 1% increase in A1c above 7%, according to a new study.

Moreover, report study authors, led by Eric Yuk Fai Wan, PhD, of the department of family medicine and primary care at the University of Hong Kong, risk of CVD event-related mortality is increased by 37%.

The paper was published online August 3, 2020, in Diabetes, Obesity and Metabolism.

The authors point to conflicting findings from several large landmark trials (eg, UKPDS, ADVANCE, ACCORD) that investigated the impact of glucose control on risk of CVD and mortality. Their aim in the current paper was to further investigate the association.

Using electronic health records from primary care clinics in Hong Kong, the retrospective cohort study looked at the effect of “usual A1c levels” on 10-year CVD risk among 174 028 individuals aged between 45 and 84 years who had a recorded diagnosis of T2D, no history of CVD, and results of at least one A1c measurement available 2 years before the baseline of 2008-2010.

Usual A1c value was calculated using a mixed effects model to minimize regression dilution bias and was determined for the entire study population to be 7.5%.

The association between usual A1c and CVD risk was assessed by Cox regression with adjustment of baseline covariates. Subgroup analyses by patient characteristics were also conducted.

Results

After a median follow-up of 8.4 years, there were 34 072 recorded CVD events and 3719 CVD-related deaths.

  • There was a curvilinear association found between usual A1c and total CVD, stroke, heart failure, and CVD mortality risk.
  • A positive linear association was observed between usual A1c and risk of outcome when A1c was ≥7%. No significant difference was found among patients with usual A1c <7%, regardless of patient characteristics.
  • Adjusted hazard ratios for CVD risk per 1% increment in usual A1c >7% 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 impact of usual A1c on younger patients was stronger vs on older patients, which the authors say suggests that low usual A1c is not necessarily protective against CVD risk. They conclude that among younger patients, strict adherence to A1c <7% could help prevent CVD.