Originally Published: 13 OCT 23 16:40 ET

By Jen Christensen, CNN

(CNN) — More young and middle-aged women are being diagnosed with lung cancer at a higher rate than men, and scientists are struggling to understand why, new research shows. Awareness of the disease’s effects on women is lacking, experts say, and the US government spends significantly less on its research than on similar studies in men.

“When you ask people what the number one cancer killer of women is, most will say that it’s breast cancer. It’s not. It’s lung cancer. Lung cancer is a women’s health disease, but we clearly need to educate more people about it,” said Dr. Andrea McKee, a radiation oncologist and volunteer medical spokesperson for the American Lung Association.

This week, McKee attended the GO2 for Lung Cancer Conference, where experts and advocates talked about disparities for women with lung cancer and the ways to help more people recognize that this “hidden” women’s cancer is a significant problem that kills about 164 women every day in the US.

Historically, McKee said, lung cancer has been considered an older man’s disease, partly because men were the early target demographic for tobacco companies, and smoking is the leading cause of lung cancer. Cigarettes were even a part of military rations in World War II.

Smoking had been largely taboo for women until it became linked with female independence, and then they began drawing tobacco companies’ notice too, historians say.

But those changes don’t entirely account for the increases in lung cancer among women. Smoking rates have declined significantly over the past couple of decades, according to the US Centers for Disease Control and Prevention, yet the cancer rate among women has inversely increased – particularly among women who have never smoked.

Research published this week in the journal JAMA Oncology found that more women ages 35 to 54 had been diagnosed with lung cancer at a higher rate than similarly aged men. This study included people diagnosed with lung cancer between 2000 and 2019.

Part of the reason is the decline in the number of men getting lung cancer, which has been larger than the decline in women. Fewer men are being exposed to carcinogens in the workplace, the researchers said, but that also can’t account for the changes.

A lack of understanding about what is driving the gender trend in lung cancer is in part driving a push to get more funding to study these differences in hopes of identifying them so public health leaders could target those particular issues.

Lawmakers are even now considering the Women and Lung Cancer Research and Preventative Services Act, which aims to boost funding and would require the US Department of Health and Human Services to determine how women are given access to lung cancer preventive services, as well as to conduct public awareness campaigns.

Only 15% of the budget of the National Institutes of Health is allocated toward female-focused research, studies show, yet lung cancer kills more women in the US than breast, ovarian and cervical cancer combined. Lung cancer is the least-funded of the major cancers in terms of research dollar per death, research shows.

Many women were left out of some large lung cancer studies, and before 1993, most testing for clinical trials also omitted women.

Research has found that lung cancer diagnoses have risen 84% in women over the past 43 years while dropping 36% in men, even though many of those women never smoked. In fact, women who have never smoked are more than twice as likely as male never-smokers to get lung cancer.

Other risk factors include family history, exposure to secondhand smoke, radon, asbestos, pollution and arsenic in drinking water, according to the American Cancer Society.

Lung cancer is so deadly in part because it’s often diagnosed late, when it’s harder to treat, despite enormous advances in treatment in recent years.

Only 5% of people who are eligible for lung cancer screening get it, according to the American Lung Association. Researchers hope that studies showing gender disparities in lung cancer will make health care providers aware of how this disease affects women so they can know to watch for it.

Individuals can watch for signs of lung cancer, too. Talk to your doctor if you have a cough that lasts more than six weeks, are coughing up blood, are short of breath or hoarse for a few weeks, or have unexplained weight loss.

The American Lung Association website also offers a quiz, Saved by the Scan, to help you find out if you are eligible to get tested.