Nearly half of all cancer deaths are associated with modifiable risk factors, including smoking, drinking alcohol and being overweight, according to a new study.

In the first known study of its kind, researchers from the University of Washington’s Institute for Health Metrics and Evaluation used data from 204 countries from 2010 to 2019 to analyze 23 cancer types and 34 behavioral, metabolic, and environmental and occupational risk factors.

They found that, in 2019, 4.45 million cancer deaths worldwide, or 44.4% of all cancer deaths, were linked to the risk factors they analyzed. The scientists also observed that those factors contributed to a 42% loss in healthy years.

The study, which was funded by the Bill & Melinda Gates Foundation, was published Thursday in The Lancet medical journal, 

Behaviorial risk factors, such as tobacco use, alcohol use, unsafe sex and dietary risks, were responsible for 3.7 million deaths, or 37% of all cancer-related deaths.

Tracheal, bronchus and lung cancer accounted for 36.9% of risk-attributable cancer deaths, more than any other form of the disease.

Cancer is the second leading cause of death worldwide, behind only cardiovascular diseases, although many cases are not preventable. 

The study also found that cancer deaths related to risk factors increased by 20.4% from 2010 to 2019.

“This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world,” Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation and one of the paper’s leading authors, said in a statement. “Smoking continues to be the leading risk factor for cancer globally, with other substantial contributors to cancer burden varying. Our findings can help policymakers and researchers identify key risk factors that could be targeted in efforts to reduce deaths and ill health from cancer regionally, nationally, and globally.”

Men are at the greatest risk, the study found. Smoking cost them nearly four times as many healthy years than women, and they lost more than three times as many healthy years to drinking alcohol. 

Men also faced increased environmental and occupational risks, leading to three times as many healthy years lost compared to women. Men are more likely than women to smoke, drink and work in places where they’re exposed to carcinogens, the researchers noted.

“Although some cancer cases are not preventable, governments can work on a population level to support an environment that (minimizes) exposure to known cancer risk factors,” the paper’s authors wrote. 

The study found that more than a quarter of risk-attributable cancer deaths occurred in wealthier, developed countries, although the authors noted that those countries account for only 13% of the world’s population, meaning poorer nations are disproportionately impacted.

In an accompanying editorial published in The Lancet, Drs. Diana Sarfati and Jason Gurney of the University of Otago in New Zealand, who were not involved in the study, wrote, “It is no accident that behaviors associated with higher risk of cancer are patterned according to poverty, particularly within countries. Poverty influences the environments in which people live, and those environments shape the lifestyle decisions that people are able to make.”

Sarfati and Gurney also wrote that “eradication or mitigation of modifiable risk factors is our best hope of reducing the future burden of cancer.”