Quitting Smoking and Diabetes

We know that quitting smoking reduces many risks to your health, and not just cancer: heart disease, emphysema and diabetes are also commonly linked to smoking. One of the reasons many of my patients cite for fearing to quit smoking, however, is the weight gain that so often seems to follow quitting. And weight gain, as we know, leads to its own health risks, including diabetes, heart disease and some cancers. So if you quit smoking, is your risk of diabetes lower (because of quitting), higher (because of the weight gain) or does it stay the same?

Researchers with Johns Hopkins, Chapel Hill and the Federal University of Rio Grande do Sul of Brazil teamed up to assess whether those who quit smoking would be more or less likely to develop diabetes (Ann Intern Med 2010;152(1):10-17). They used information gathered during a prospective study known as the Artherosclerosis Risk in Communities (ARIC), which included over 15,000 middle-aged adults in the United States and lasted over 17 years. At the start of the study and at regular intervals until 2004, the participants in the study were assessed by the ARIC researchers for Body Mass Index, blood pressure, cholesterol and glucose levels, and demographics such as amount of exercise and education.

First the diabetes researchers excluded those people who already had diabetes at the start of the study, as well as those who had asthma, lung disease or heart disease, which left them with over 9,000 participants in the study.

Current and former smokers were then grouped into three levels of "pack-years:" low, medium and high. (Pack Years are the average number of cigarettes smoked per day, multiplied by how many years the person smoked and divided by 20, the number of cigarettes in a pack).

Those who developed diabetes at the close of the study were then compared to those who did not. Unsurprisingly, those participants who had the highest number of Pack Years were almost 150% more likely to develop diabetes than those who never smoked, even when Body Mass Index and other risk factors were taken into account.

Of concern, however, is that for those who did quit smoking, their risk of diabetes actually increased (to about 175%) in the first three years after they quit. That risk decreased during the first twelve years of not smoking, however, to be the same as those who had never smoked. The good news is that the researchers then examined the new smokers for weight gain and found that those who gained the most after quitting were also those whose risk increased the most in those first three years.

What this means for you

If you're a smoker and are thinking about quitting, don't let this study stop you. Enlist your doctor's help in quitting. The risks of continuing to smoke far outweigh the risks of gaining weight after you quit.

First posted: January 13, 2010