May 9 (UPI) -- Smoking can't explain why women are more at risk for COPD , a new study says. Women are about 50% more likely than men to develop COPD even though they are less likely to smoke, researchers reported Thursday in the journal BMJ Open Respiratory Research . Smoking tobacco is the main cause of COPD, the umbrella term for chronic breathing problems like emphysema and bronchitis, researchers say. But the COPD rate is higher among women than men, even though women don't smoke as much