Secondhand smoke may be the cause of many cases of lung cancer among women: research shows that up to 20 percent of women who get the disease have never smoked, Reuters reported Feb. 9.

Among men, about 9 percent of lung-cancer patients are nonsmokers, according to researcher Heather Wakelee of Stanford University. "And because of the stigma, people are embarrassed to speak out about their disease," she said. "They feel like as soon as they say they have lung cancer, everyone judges them."

Wakelee drew her conclusions from surveys of more than 1 million people ages 40-79. The study authors said it was unclear why so many female nonsmokers get lung cancer, but noted that more women than men may be exposed to secondhand smoke.

The study appears in the February 2007 issue of the Journal of Clinical Oncology.