Lung cancer rates have been falling faster in men than in women, a trend that has now extended from younger women to those over 50, a new study from the American Cancer Society (ACS) has shown.

The researchers looked at the rate of lung and bronchus cancers diagnosed from 2000 to 2019 and saw the rates of decline between 2000-2004 and 2015-2019 were greater in men than women. Previous studies have shown the rate of lung cancer has been higher in younger women than in men, but this new analysis extended that trend to women over 50.

Among people from 50-54, the rate per 100,000 fell 44% in men, but dropped only 20% in women in that age group, the ACS researchers determined.

“These findings are very concerning,” said Dr. Ahmedin Jemal, senior vice president, surveillance and health equity science at ACS and lead author. “We don’t know why lung cancer incidence rates among younger and middle-aged individuals are now higher in women than men, reversing the historical pattern.”

Jemal points out that cigarette smoking among younger women is not higher than in men but that it is still a major contributor to lung cancers.

“Lung cancer is still the leading cause of cancer death in the U.S. with 80% of cases and deaths caused by cigarette smoking,” said Jemal. “To mitigate the high burden of the disease in young and middle-aged women, greater effort is needed to promote smoking cessation at provider and community levels, improve access to smoking cessation aids and programs through expansion of Medicaid, and increase lung cancer screening in eligible women.”

The ACS analysis further showed that women over 55 continued to have a lower cancer rate than men, although the difference has been shrinking.