Type 2 diabetics who quit smoking are likely to see a temporary deterioration in their glycaemic control which could last up to three years, according to a recent study.

Researchers at Coventry University examined the primary care records of more than 10,000 adult smokers with T2DM over six years to investigate whether or not quitting was associated with altered diabetes control.

"Knowing that deterioration in blood glucose control occurs around the time of stopping smoking helps to prepare those with diabetes and their clinicians to be proactive in tightening their glycaemic control during this time," researcher Dr. Deborah Lycett said in a statement.

The study found that in the 3,131 (29%) people who quit and remained abstinent for at least one year, HbA1c - which is an average measurement indicating how well the body is controlling blood glucose levels - increased by 2.3mmol/mol (0.21%) before decreasing gradually as abstinence continued.

They found that 5,831 (55%) continual smokers -- who did not change their smoking status during the study -- experienced a more gradual increase in HbA1c in that same period. The HbA1c levels in quitters became comparable with the levels seen in continual smokers three years after quitting.

Previous studies have shown that a 1 percent (11mmol/mol) reduction in the HbA1c level of someone with diabetes will result in them being 16 percent less likely to suffer heart failure and 37 percent less likely to experience microvascular complications -- indicating the significance of small percentage changes in HbA1c levels.

The researchers used a regression model which examined each cohort with and without weight change data, concluding that weight changes often associated with quitting smoking did not significantly alter the association between smoking cessation and HbA1c levels.

"Stopping smoking is crucial for preventing complications that lead to early death in those with diabetes. So people with diabetes should continue to make every effort to stop smoking, and at the same time they should expect to take extra care to keep their blood glucose well controlled and maximize the benefits of smoking cessation," Lycett added.

The findings are detailed in The Lancet Diabetes & Endocrinology.