Smoking Reverses Benefits of Inhaled Insulin

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The effect of smoking cessation and subsequent resumption on absorption of inhaled insulin, by R.H.A. Becker and colleagues. Diabetes Care 29:277–282, 2006.

Why did the researchers do this particular study?

In February 2006, inhaled insulin was approved by the Food and Drug Administration. The researchers wanted to see how smoking affects how the lungs absorb inhaled insulin and how quickly the insulin acts in smokers.

Who was studied?

Twenty healthy male smokers and ten healthy male nonsmokers. None of the individuals had diabetes.

How was the study done?

The researchers measured how fast insulin was absorbed and how fast it acted in all of the men after they took a one-milligram dose of inhaled insulin. All of the smokers were then given inhaled insulin 12 hours, 3 days, and 7 days after quitting smoking, and again, the researchers measured how fast the insulin was absorbed and how fast it acted. The smokers then started smoking again for two to three days before again receiving inhaled insulin 1 hour after their last cigarette.

The researchers compared how fast the insulin was absorbed and how fast it acted in the smokers when they took their first dose of inhaled insulin, on the three occasions after they stopped smoking, and after they started smoking again. They also compared these measurements with the measurements taken from the ten nonsmokers.

What did the researchers find?

The highest levels of insulin in the blood were much higher in smokers than in nonsmokers. The time it took to reach peak levels was also shorter in smokers than in nonsmokers.

After quitting smoking, insulin absorption slowed down within one week and got closer to the levels of nonsmokers. This was completely reversed when the men started smoking again.

What were the limitations of the study?

This study included a pretty small group of individuals and included men only. Nevertheless, it reinforces recommendations that all people, whether they have diabetes or not, should stop smoking altogether.

What are the implications of the study?

Inhaled insulin should not be used in people with diabetes who choose to continue to smoke because rapid changes in insulin levels can lead to hypoglycemia, or very low blood glucose levels. People with diabetes who smoke must quit smoking before beginning treatment with inhaled insulin. This conclusion is consistent with the recommendation that people with diabetes should not smoke at all.

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