NEW YORK (Reuters) ¿ Women who smoke are at greater risk than male smokers of developing lung diseases such as emphysema and chronic bronchitis, research from China suggests.

Such illnesses, known collectively as chronic obstructive pulmonary disease (COPD), are the second leading cause of death in mainland China, Dr. Fei Xu of Nanjing Medical University in Nanjing and colleagues note.

Cigarette smoking and exposure to indoor air pollution from burning coal and other fuels are known COPD risk factors, the researchers add, but no research in urban or rural China has investigated the amount that smoking contributes to COPD risk.

To measure the relationship and clarify the role of indoor air pollution, the researchers compared 1,743 people with COPD to 1,743 healthy controls matched by age, sex and residence. Just over half of the men in the study were smokers, while 5.3 percent of the women smoked. Participants who smoked were divided into three groups based on how many cigarettes they had smoked in their lifetime.

Smokers who consumed the fewest cigarettes had a 40 percent greater risk of COPD, the middle group of smokers had a 55 percent increased risk and the heaviest smokers had a 77 percent greater risk.