JDRF, the type 1 diabetes charityNewsHow does smoking affect type 1 diabetes?

How does smoking affect type 1 diabetes?

Posted on 11 January 2019

People with type 1 diabetes who give up smoking have similar HbA1cs to people who have never smoked, according to a recent study.

The rates of vision and kidney-related complications were also similar between the two groups.

By contrast, smokers experienced higher HbA1cs and higher rates of complications.

These findings are encouraging as they suggest that stopping smoking can help to protect against complications of type 1 diabetes.

Why did they do this research?

We know that smoking cigarettes can lead to a number of heath conditions in people with and without type 1 diabetes.

Previous evidence however suggests that smoking can increase the risk of diabetes-related complications in people with type 1 diabetes, such as kidney disease and retinopathy.

The researchers therefore decided to analyse medical data from participants from the landmark Diabetes Control and Complications Trial (DCCT), which ran from 1983-1993.

The DCCT demonstrated that intensive insulin therapy – where insulin is given to keep glucose levels within a healthy range as much as possible – helps people with type 1 reduce the risk of complications and live healthier, longer lives.

What did they do?

The researchers looked at the health records of the 1441 participants from the DCCT.

This included analysing HbA1c levels, smoking status and the development of complications logged over the years, and how they were related to each other.

What did they find?

By the end of the trial, smokers had higher Hba1c levels than people who had never smoked or had given up smoking, by over 0.30% points.

In addition, smokers had a 43% and 36% increased risk of developing retinopathy and kidney complications respectively, when compared with people who had never smoked.

The researchers found that this was the case because smoking leads to a higher HbA1c, which in turn is linked with greater risk of developing complications.

People who had given up smoking however had similar HbA1cs to people who had never smoked, and similar rates of complications.

What does this mean for type 1 diabetes?

It’s encouraging to see that people who gave up smoking had similar HbA1c levels and risk of complications to people who had never smoked.

This suggests that the negative effects of smoking on type 1 diabetes do not persist when someone quits.

In their paper, the researchers concluded:

“Former smokers can achieve similar glycemic control to never smokers and reduce their risk of complications. The results of this study should be used to encourage individuals with type 1 diabetes to avoid smoking or to quit as soon as possible.”


Our JDRF University Toolkit offers advice on smoking and drugs for people living with type 1 diabetes. 

The NHS offers advice on quitting smoking. Find out more at www.nhs.uk/smokefree.


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