Secondhand Smoke Linked to Diabetes & Obesity

Previously, a number of studies have suggested an association between cigarette smoking and an increased rate of Type 2 diabetes – despite the fact that most smokers are leaner than nonsmokers and obesity is a risk factor for Type 2 diabetes. Theodore C. Friedman, from Charles R. Drew University (California, USA), and colleagues explored whether a relationship exists between Type 2 diabetes and passive, or secondhand, smoking. The team analyzed data collected on more than 6,300 adults who participated from 2001 to 2006 in the National Health and Nutrition Examination Survey (NHANES), examining the levels of serum cotinine, a metabolite of nicotine that measures a person’s exposure to tobacco smoke. The investigators defined current smokers, which made up 25% of the sample, as survey participants who reported that they smoke cigarettes and who had a measured serum cotinine level greater than 3 nanograms per milliliter (ng/mL). Nonsmokers (41% of the sample) were those who answered “no” to the question “Do you smoke cigarettes?” and who had a cotinine level below 0.05 ng/mL. Participants who answered “no” to this question but whose cotinine level was above 0.05 ng/mL were defined as secondhand “smokers” (34% ). They found that, compared with nonsmokers, secondhand smokers had a higher measure of insulin resistance, a condition that can lead to Type 2 diabetes; higher levels of fasting blood glucose, or blood sugar; and a higher hemoglobin A1c, a measure of blood sugar control over the past three months.  Secondhand smokers also had a higher rate of Type 2 diabetes, as defined by a HbA1c greater than 6.5%. Secondhand smokers had a similar rate of diabetes to that of current smokers, and also had a higher body mass index (BMI), a measure of body fat, compared with nonsmokers, Friedman reported.  Current smokers had a lower BMI than nonsmokers but a higher HbA1c. When the researchers controlled for BMI, they found that secondhand smokers and current smokers still had a higher HbA1c than did nonsmokers.  Commenting that:”This finding shows that the association between secondhand smoke and Type 2 diabetes was not due to obesity,” the lead author submits that: “more studies are needed to show whether secondhand smoke is a cause of diabetes.”