"Knowing that deterioration in blood glucose control occurs around the time of quitting smoking helps to prepare those with diabetes and their clinicians become proactive in tightening their glycemic control during this time," said principal investigator Deborah Lycett from Coventry University.
The research team examined the primary care records of 10,692 adult smokers with Type-2 diabetes over six years to investigate whether or not quitting was associated with altered diabetes control.
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 (millimoles/moles) or 0.21% before decreasing gradually as abstinence continued.
In the same period, 5,831 (55%) continual smokers who did not change their smoking status during the study experienced a more gradual increase in HbA1c.
Previous research has shown that a one percent (11mmol/mol) reduction in the HbA1c level of someone with diabetes will result in them being 16% less likely to suffer heart failure and 37% less likely to experience microvascular complications -- indicating the significance of small percentage changes in HbA1c levels.
"Quitting 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 said.
The findings were detailed in the journal The Lancet Diabetes & Endocrinology.