PARIS (AFP) -- Breathing in other people's smoke boosts the risk of developing diabetes, according to a U.S. study published online Friday by the British Medical Journal (BMJ).

Researchers examined more than 4,500 men and women in Birmingham, Alabama; Chicago; Minneapolis, Minnesota; and Oakland, California.

The volunteers' health and smoking habits were first assessed in 1985, and again 15 years later.

The investigators found that during this time, 22 percent of smokers developed glucose intolerance -- when the body can no longer produce the hormone insulin that regulates blood sugar, and is the precursor to diabetes.

Non-smokers who were frequently exposed to second-hand smoke came next, with 17 percent developing the disease.

Those least at risk were non-smokers who were not exposed to other people's smoke. Under 12 percent of people in this group developed glucose intolerance.

The study, lead-authored by Thomas Houston of the Birmingham Veterans Affairs Medical Center, speculates that toxins from tobacco smoke could accumulate in the pancreas, where insulin is produced, but says further work is needed to confirm this.

Passive smoking was first pinpointed as a health risk in 1992. It has been associated with heart disease and cancer but not, until now, with diabetes.

Recent studies have suggested that passive smoke may contain more dangerous ingredients than previously thought.

Smoke that is released from a cigarette between puffs is cooler than smoke that is directly inhaled. The lower temperature thus leaves some toxic compounds unreduced.