Obese smokers may have a six to eight times greater risk of dying compared with normal weight people who never smoke, a new study showed.

In addition, among smokers with a large waist, the risk of dying was five times greater than among people with the smallest waists who never smoked, said the study conducted by researchers at the U.S. National Institute on Aging (USNIA).

The study found that as weight increased, so did the rate of death. Across all weights, people who smoked had the highest death rates.

"We know that obesity and smoking by themselves are important health risk factors," said lead researcher Annemarie Koster, a USNIA epidemiologist. "We found that smoking and obesity are independent predictors of mortality, but smoking and being obese especially increases the mortality risk."

Smoking and obesity both carry a significant mortality risk, but particularly smoking, Koster said. "It seems that smoking cessation was associated with significantly lower mortality risk in every weight group," she said. "Quitting smoking will definitely improve your mortality risk, no matter in what weight group you are."

Losing weight will also lower mortality risk, Koster said. "Both losing weight and quitting smoking will increase your health and lower your mortality risk," she said.

The report was published in the November issue of The American Journal of Clinical Nutrition.

For the study, Koster's group collected data on 3.5 million people, aged 50 to 71. In 1995-1996, and again in 1996-1997, questionnaires were sent out, asking people about diet, family history of cancer, physical activity, hormone replacement therapy, weight, waist size, and smoking.

Using the U.S. Social Security Administration Death Master File, the researchers linked the data with death records of the survey participants from 1996 to 2006. During that period, almost 20,000 men and 7,500 women died.

(Xinhua News Agency November 12, 2008)