Can secondhand smoke lead to diabetes?

Breathing secondhand smoke may increase your chances of developing type 2 diabetes and obesity, according to the Endocrine Society.

A new study from Charles Drew University found that adults exposed to environmental tobacco smoke had a higher measure of insulin resistance than nonsmokers without the smoke exposure.

With insulin resistance, the body produces insulin but does not use it properly. It can eventually lead to type 2 diabetes.

"Passive cigarette smoking"

Researchers measured "passive cigarette smoking" by how much cotinine they found in the blood of participants. Cotinine is a substance related to nicotine that measures a person's exposure to tobacco smoke.

While 75 percent of the 6,300 participants said they didn't smoke cigarettes, 34 percent had a high enough level of cotinine in their blood to be considered secondhand "smokers."

Current smokers made up 25 percent of the participants, while 41 percent were nonsmokers with low cotinine levels.

What is secondhand smoke?

Secondhand smoke is a mixture of two forms of smoke that come from burning tobacco, according to the American Cancer Society.

The first form is sidestream smoke, the smoke that comes from the end of a lighted cigarette, pipe or cigar. The second form is mainstream smoke, the smoke that is exhaled by the smoker.

Compared to mainstream smoke, sidestream smoke has higher concentrations of carcinogens that can cause cancer. It also contains smaller particles than mainstream smoke; these particles can make their way into the body's cells more easily.

More than 250 of the 7,000 chemicals in tobacco smoke are known to be harmful, and at least 69 are known to cause cancer, says The American Cancer Society.

Secondhand smoke means higher blood glucose

With regard to diabetes, secondhand smokers had higher levels of fasting blood glucose than nonsmokers, the researchers found.

A test of fasting plasma glucose measures blood glucose when a person hasn't eaten for at least eight hours. A high level can detect diabetes and prediabetes.

The passive cigarette smokers in the study also suffered from higher hemoglobin A1c. This measures a person's average blood glucose levels over a three-month period.

Current smokers and secondhand smokers both had a higher hemoglobin A1c than nonsmokers did. Hemoglobin A1c levels greater than 6.5 percent indicate diabetes.

More diabetes than nonsmokers

Secondhand smokers in the study also had a higher rate of type 2 diabetes than nonsmokers.

This is a similar rate of diabetes to current smokers, according to Theodore C. Friedman, MD, PhD and co-author of the study.

"More effort needs to be made to reduce exposure of individuals to secondhand smoke," said Friedman.

Obesity risk factor

Secondhand smokers in the study also had a higher body mass index (BMI) than nonsmokers.

A high BMI indicates overweight and obesity, a major risk factor for developing type 2 diabetes.

"The finding shows that the association between secondhand smoke and type 2 diabetes was not due to obesity," said Friedman. "More studies are needed to show whether secondhand smoke is a cause of diabetes."

Source: Endocrine Society, American Cancer Society