A new, first-of-its-kind global study found that nearly 1 in 2 cancer deaths — an estimated 4.45 million a year — can be attributed to preventable risk factors, with smoking, high body mass index (BMI), and drinking too much alcohol topping the list.
Although cancer is the second leading cause of death worldwide (after heart disease) this is the first study to look at a multitude of factors on a global level, according to the authors. The findings were published on August 20 in The Lancet.
“This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world. Smoking continues to be the leading risk factor for cancer globally, with other substantial contributors to cancer burden varying,” said Christopher Murray, MD, DPhil, co-senior author and IHME director, in a statement.
It's important that the associations between preventable risk factors and cancer is finally getting the coverage it deserves, says Suneel Kamath, MD, a medical oncologist at Cleveland Clinic in Ohio, who was not involved in this study. “Technically, smoking is still the biggest cause of cancer and cancer-related death in the United States, but since that has been so well described, I think highlighting obesity and overweight is even more important,” he says.
Cancer Deaths Due to Preventable Risk Factors Rose by 20 Percent in the Last Decade
Using data from the 2019 Global Burden of Disease study by The Lancet, the most comprehensive research to date on the impact of diseases around the world, investigators examined how 34 different behavioral, metabolic, environmental (such as pollution and climate change), and occupational (associated with a person’s job) risk factors contributed to deaths and ill health due to 23 cancer types.
Changes in cancer burden between 2010 and 2019 due to risk factors were also estimated based on mortality and disability-adjusted life years (DALYs), a measure of years of life lost to death and years lived with disability.
Investigators found that between 2010 and 2019, cancer deaths due to risk factors rose by 20.4 percent globally, increasing from 3.7 million to 4.45 million. Ill health due to cancer increased by 16.8 percent over the same period, rising from 89.9 million to 105 million DALYs.
Cancer Deaths Due to Preventable Risk Factors Higher in Wealthier Countries
In 2019, risk-attributable cancer deaths globally occurred disproportionately in wealthier countries — these countries had 26.5 percent of the cancer deaths although they accounted for 13.1 percent of the global population.
The five regions with the greatest cancer death rates due to risk factors were Central Europe, East Asia, high-income North America, Southern Latin America, and Western Europe.
Smoking Still No. 1 Risk Factor for Cancer Deaths Around the World
Researchers named smoking as the risk factor that caused the most cancer deaths, and lung and lung-related cancers — including tracheal cancer (which starts in the windpipe) and bronchus cancer (appearing in the bronchi, the large airway of the lungs) — accounted for 36.9 percent of all cancer deaths attributable to risk factors.
Lung cancer is among the top 3 most commonly diagnosed types of cancer in both men and women, per the National Cancer Institute. In the United States, 80 to 90 percent of lung cancer deaths are linked to cigarette smoking, per the Centers for Disease Control and Prevention.
The Connection Between Obesity and Overweight and Cancer Risk
This was followed by colon and rectum cancer (13.3 percent), esophageal cancer (9.7 percent), and stomach cancer (6.6 percent) in men, and cervical cancer (17.9 percent), colon and rectum cancer (15.8 percent), and breast cancer (11 percent) in women.
“I am a little surprised by how large the number of cancer cases associated with smoking, alcohol, and obesity is, but only a little — I expected it to be large,” says Dr. Kamath.
The association of smoking and drinking with different types of cancer — and not for only lung cancer due to smoking and liver cancer caused by consuming too much alcohol — has been well established, but obesity and cancer risk is an important factor that is often overlooked, he says. “The fact that obesity and overweight cause cancer is definitely new and really important to highlight.”
Overweight and Obesity Play Key Role in Contributing to Cancer Risk in U.S.
It’s estimated that in 2022, there will be 1,918,030 new cancer cases and 609,360 cancer deaths, according to the American Cancer Society.
For Americans, obesity and overweight are key areas to address when it comes to efforts to prevent cancer, as 73.6 of Americans have either obesity of overweight, says Kamath. A person with a BMI from 25 to 29.9 is considered overweight, and a person with a BMI of over 30 is considered to be obese. Per the National Heart, Lung, and Blood Institute, BMI is calculated based on a person’s weight and height and the same formula is used for both men and women.
“This is the main reason why life expectancy is shortening in the U.S. for the first time in a long time — we have to work on this,” says Kamath.
Prevention ‘Always Works Much Better Than Treatment’ In Cancer Care
“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,” said Dr. Murray.
“As much as early detection of cancer is important, many people who have cancers that are initially caught early will go on to have progression to advanced stages and die of their cancer,” says Kamath. And unfortunately, we will probably never be able to screen and detect all cancers early for everyone, he adds.
“Prevention always works much better than treatment in cancer care. The best way to affect modifiable behaviors like diet, smoking, or alcohol is at a systems and policy level to guide people to choose the rights for themselves, rather than forcing something on them,” says Kamath.
He points to policies like the U.S. Food and Drug Administration requiring tobacco companies to cut down on the amount of nicotine in cigarettes or banning flavored cigarettes or marketing to young people. “Insurance companies or employers incentivizing weight loss with lower premiums could be another example,” he says, adding that more of those types of prevention strategies are needed.