Diabetes and smoking
Few people know it, but smoking increases your risk of contracting diabetes. Furthermore, diabetic smokers are more likely to develop other complications. Here are the details based on existing research.
Smoking puts people at higher risk of contracting type 2 diabetes
Numerous studies carried out since the 1990s have highlighted a link between smoking and type 2 diabetes. A study carried out in 1996 showed that the prevalence of smoking among diabetic patients is significantly higher than that among non-diabetic patients (27% vs. 33%). Well before that, a cohort study carried out between 1959 and 1972 (on 275 190 men and 434 637 women) found that smokers ran an increased risk of contracting diabetes and that the more they smoked, the higher the risk was. Among those who smoked fewer than 20 cigarettes a day, men had a 5% higher risk and the risk for women was not higher. For people who smoked 20 to 40 cigarettes per day, the increase was 19% for men and 21% for women. And for those who smoked more than 40 cigarettes a day, the risk rose to 45% for men and 74% for women. (1) The Physicians Health Study showed that smokers of fewer than 20 cigarettes a day ran a 50% higher risk of developing type 2 diabetes than non-smokers, while those who smoked more than 20 cigarettes a day increased their risk by 70%. According to recent studies, the percentage of type 2 diabetes cases attributable to smoking stands at 2%. This rate may, however, be much higher for heavy smokers. Several explanations have been put forward for the link between smoking and diabetes, including the idea, advanced by some studies, that the substances contained within tobacco, and in particular nicotine, affect the body's sensitivity to insulin. As a cigarette contains 3 500 different components, and 500 gaseous components are released when it is burned, it is difficult to determine precisely which component is responsible. Smoking also has a significant clinical effect on intravenous and oral tests for glucose tolerance, which could influence the detection of diabetes. This could be directly linked to nicotine or to other components. Two cohort studies have studied the effect of smoking cessation. That of Will et al. showed that when men stopped smoking for 10 years and women stopped smoking for 5 years, the risk of developing diabetes fell to the same level as for non-smokers. (2) The second study indicated that quitting smoking produced visible benefits on middle aged men after 5 years and that the risk of diabetes had fallen to the level of that of non-smokers after 20 years. (3) It's therefore best to stop smoking as early as possible!
Diabetic smokers run a higher risk of complications
Smoking worsens the complications of diabetes, whether it's type 1 or type 2. We know that the risk of complications associated with both smoking and diabetes is nearly 14 times higher if you have both of these risk factors than if you have only one. Evidence from studies on diabetes shows the very strong link between smoking and mortality. Smoking basically presents an increased risk of macro-vascular complications (strokes, heart attacks) and micro-vascular complications (kidney failure, sight problems, nerve damage) which lead to more chronically ill people in the population and a higher mortality rate. Various studies have shown that smokers secrete more albumin than non-smokers, which is linked to the second group of health problems because it can lead to microalbuminuria, where small quantities of protein are present in the urine. This is the first sign of deterioration in kidney function. The risk of microvascular complications is higher for type 1 diabetes. The risks of macrovascular complications (problems with the arteries, strokes, etc.) are higher for people who have type 2 diabetes. The UK Prospective Diabetes Study has demonstrated that smoking constituted an important, independent risk factor for macrovascular complications in sufferers of type 2 diabetes. (4) Smoking cessation is therefore of prime importance in the treatment of diabetes, for both the control of blood sugar levels and for limiting the development of complications. Various studies have highlighted the importance of quitting smoking as soon as possible after diabetes is diagnosed.
Specific things that diabetics should bear in mind when quitting smoking
Diabetics who smoke often exhibit a high level of dependency and find it difficult to quit. In a study by Ardron et al. involving 60 people, only one had managed to quit smoking after 6 months. (5) Furthermore, diabetic smokers who are hospitalized seem less interested in smoking cessation programs than other patients (6) and smoking cessation proves difficult for diabetics. Several possibilities have been put forward to explain why diabetics find it so difficult to quit. The fear of gaining weight is first and foremost .Various studies have shown that diabetics think that smoking helps them to eat less and thus to control their weight. However, weight gain after quitting smoking is generally minimal and presents less of a health risk than carrying on smoking. In addition, it is possible to limit potential weight gain when quitting by practicing moderate physical exercise. Diabetics also have a higher risk of suffering from depression than the rest of the population. That often leads to a higher rate of tobacco consumption and we know that stress can hinder smoking cessation. For these reasons, smoking cessation programs should be adapted to serve diabetic people. The level of dependency on cigarettes should be evaluated by each individual diabetic smoker. In order to manage it, we recommend that diabetic smokers try nicotine replacement therapy which can be supplemented by cognitive-behavioral therapy. It may also be useful to include support concerning nutrition, to help patients control their weight while quitting. Lastly, it would be useful to assess their psychological state: depressive diabetics or those who have a history of depression should be helped accordingly, by therapies and/or medication. In order to make diabetics more aware of the risks of smoking, the idea of a "glucose equivalent" has been developed in diabetes treatment clinics in Taiwan. Based on the study of a large cohort of patients from Asia, the risk posed by smoking is said to be equivalent, on average, to a 41mg/dl increase in blood sugar in a non-diabetic and 68mg/dl increase in a diabetic. This concept could help doctors to convince diabetic smokers of the need to quit. Finally, young people suffering from type 1 diabetes deserve a mention. These people represent a vulnerable group because it seems that they are more likely to turn to smoking after first being diagnosed with diabetes. Prevention and cessation programs should therefore be specially targeted at them.
Author: Anne-Sophie Glover-Blondeau, August 2012.
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