Study: Young Women Now Have Higher Rates for Lung Cancer Than Men Worldwide

Women between the ages of 30 to 49 are being diagnosed with lung cancer at higher rates than men, at the same age and in many high-income countries, according to a new study published in the International Journal of Cancer. Even though smoking is the major risk factor for causing all types of lung cancer, the authors said that differences in smoking between men and women do not completely explain the pattern.

The study involved cancer researchers in Canada, France, and  Ahmedin Jemal, DVM, PhD, and Lindsey A. Torre, MSPH from the American Cancer Society (ACS). They looked at incidence rates, which are the number of people diagnosed with lung cancer in the same year and country. They compared the rates between men and women:

• in 5-year age groups, starting with 30 to 34 up to 60 to 64
• in 40 countries across 5 continents, and
• over 5-year intervals, starting with 1993 to 1997 and ending with 2008 to 2012.

During those years, the incidence rates of men generally decreased across all ages in all countries. For women, the trend across countries was for the rates to remain the same or decline, but at a slower pace compared to men.

Historically, lung cancer rates have been higher in men mainly because of their smoking patterns. During the most recent period of the study, however, the rate was higher in women ages 30 to 49 in 6 countries: Canada, Denmark, Germany, New Zealand, the Netherlands, and the US. The researchers found similar, but not statistically significant, trends in 23 other countries and across different levels of economic development, including several countries in Afria and Asia.

The higher rates in women were largely driven by the increases in adenocarcinoma, a type of lung cancer seen in people who smoke. This type of lung cancer  is also the most common type seen in people who don't smoke and is more likely to occur in young women.   

“In most of the countries where young women [ages 30 to 49] had higher rates of lung cancer than young men, we found that women were smoking almost as much as men, but not more than them,” said Jemal, Scientific Vice-President of the ACS Surveillance and Health Services Research program. “This suggests that differences in the way men and women smoke doesn’t fully explain why the diagnosis rates in young women were higher than in young men.”

It’s possible that the higher risk of lung cancer in women is related to changes in the make-up of cigarettes over the years or the way women respond to the cancer-causing substances in tobacco, Jemal said.  For instance, he noted: 

• More women started smoking in the years when filtered cigarettes were most common. Filtered cigarettes increase the risk of adenocarcinoma lung cancer due to the way tobacco smoke is distributed to the outer parts of the lungs.
• Women may have different genetic risk factors for lung cancer than men, such as not being able to repair damaged DNA or having abnormal genes related to cancer development. 

The authors called for more studies to identify reasons for higher lung cancer rates in women in many countries.

“Our findings forewarn of a higher lung cancer burden in women than men at older ages in the decades to follow, especially in higher-income areas,” said Jemal. He and the other authors recommend continued, yet intensified, actions to help people stop smoking and prevent them from starting to smoke or using other tobacco products.

This study was an extension to a previous study about higher incidence rates of lung cancer in young women than young men in the US,  published in the New England Journal of Medicine in 2018 and written by researchers from the ACS and the National Cancer Institute’s Division of Cancer Epidemiology and Genetics.