Smoking, diabetes and complications – what’s the connection?

Smoking is the cause of a number of diseases. Diabetes is also on this list. A smoker’s risk of getting diabetes is 30-40% higher, and for those people who have already been diagnosed, smoking can cause severe problems in self-control. We talk about the relationship between smoking, diabetes and the progression of complications.
Smoking and life expectancy
The largest study of the effects of smoking was carried out by British scientists – Sir Richard Doll and his colleague Sir Richard Peto. They looked at 50 years of data on 34,439 men. During the course of their work, they concluded:
“The factors that have led to gradual and significant declines in non-smoking mortality rates over the past half century – prevention and improved treatment of disease – are completely outweighed by tobacco smoking. Regardless of the improvement in the quality of life, and in particular medical care, among smokers, on the contrary, there is a gradual increase in the mortality rate. This coefficient is directly related to the intensity of cigarette use and the age of the onset of addiction.
The average smoker dies about 10 years earlier than a non-smoker with otherwise similar lifestyles. If a smoker quits smoking, then the age when he did this gives a corresponding increase in years of life. Quitting smoking at 60, 50, 40, or 30, respectively, saves about 3, 6, 9, or 10 years of life expectancy.
Smoking is one of the causes of diabetes
The US Surgeon General’s 2014 report states the following:

  1. There is enough evidence to conclude that smoking causes diabetes.
  2. The risk of developing diabetes is 30-40% higher for active smokers than for non-smokers.
  3. There is a positive dose-response relationship between the number of cigarettes smoked and the risk of developing diabetes.
    The Surgeon General came to this conclusion after a meta-analysis of 46 studies involving more than 3.9 million people, of whom 140,813 had diabetes.
    The analysis controlled for age, gender, ethnicity, BMI, waist circumference and waist-to-hip ratio, diet, physical activity, alcohol use, family history of diabetes, education, fasting glucose, insulin, and lipid profile. Even when the largest studies were excluded and potentially biased publications corrected, the data showed a significantly increased rate of newly diagnosed diabetes among smokers.
    A meta-analysis of 88 studies (5,853,952 participants) in 2015 found the relative risk of developing type 2 diabetes among smokers compared to non-smokers. For those who quit smoking, the risk decreases from 1.37 to 1.14 (1.10-1.18) compared with non-smokers. Even passive smoking raises the risk of developing diabetes by 1.22 (1.10–1.35) compared to those who were not exposed.
    The authors claim:
    ‘Based on the assumption that the association between smoking and diabetes risk is causal, we estimate that 11.7% of cases of type 2 diabetes in men and 2.4% in women (i.e. about 27.8 million cases in all world) were associated with active smoking.”
    Twenty-seven million!
    Quitting smoking reduces the risk of developing type 2 diabetes. One study compared people who never smoked, smokers who quit less than five years ago, and those who gave up the habit 10 years ago or more. Regarding non- smokers, those who quit smoking 5 years ago, the risk score was 1.54 (1.36–1.74), while those who stopped 10 or more years ago had a relative risk of 1.11 (1.02–1.20).
    Mortality and Complications
    Heart and mortality
    Smoking kills whether you have diabetes or not. But people with diabetes need to be aware of the increased risk of cardiovascular disease. And if you smoke with diabetes, the situation only gets worse. Smoking cessation leads to a reduced risk of complications and premature death on all counts. In the ADVANCE study, men and women who quit smoking reduced their risk of all-cause mortality by 30%.
    Dabetic foot
    Smoking is associated with the development, progression and worsening of the treatment of diabetic foot. A meta-analysis has shown that diabetic foot problems are more severe in smokers with diabetes, incl. there are more amputations. This is important because today we know that it is not the disease itself that leads to such an operation, but very poor control, lack of timely treatment and low awareness of self-control and compensation issues.
    Blood flow and nutrition of the retina
    Smoking (presumably through nicotine) reduces retinal blood flow, in addition to the broader effect of lowering the oxygen-carrying capacity of the blood through an increase in carboxyhemoglobin.
    Hypoxia increases the risk of progression of diabetic retinopathy. Smokers are more likely to develop retinopathy than non-smokers. Studies on the effect of smoking on retinopathy have been mixed.
    A recent meta-analysis has shown that in type 1 diabetes, smoking increases the risk of both diabetic retinopathy in general and proliferative retinopathy in particular when compared with non-smokers.
    Read more about the classification of retinopathy in diabetes.
    Kidney health in smokers with diabetes
    The meta-analysis also compared people with nephropathy with and without diabetes. Smoking significantly increases the risks in people with diabetic nephropathy: a value of 1.70 (1.48–1.95) compared with those with non-diabetic nephropathy.
    Smoking cessation and blood sugar
    Quitting smoking can positively impact blood glucose balance and the quality of diabetes care.
    Obviously, it is better not to use nicotine products at all. However, many people find it impossible to quit smoking. E-cigarettes are considered to be 95% safer than traditional cigarettes (apart from recent news that e-cigarettes cause lung disease). Although they do not contain tar, they still contain nicotine, cigarette delivery components and flavors. The products contained in e-cigarettes have not been in widespread use long enough to assess their impact, incl. among people with diabetes.

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