Editor's note: This popular story from the Daily Briefing's archives was republished on Mar. 1, 2019.
Nearly half of all cancer deaths and more than 40% of cancer cases are attributable to potentially modifiable lifestyle factors, according to a study published by researchers at the American Cancer Society (ACS).
For the study, researchers looked at the number and proportion of invasive cancer cases, as well as deaths for 26 types of cancer, among U.S. adults ages 30 and older in 2014 that were the result of "major, potentially modifiable exposures." Those exposures included:
- Alcohol consumption;
- Cigarette smoking;
- Consumption of red and processed meat;
- Excess body weight;
- Low consumption of fruits, vegetables, dietary fiber, and calcium;
- Physical inactivity;
- Secondhand smoke;
- Six cancer-associated infections, including HPV; and
- Ultraviolet radiation.
The researchers drew cancer prevalence data from CDC and the National Cancer Institute; cancer death data from CDC; risk factor prevalence estimates from nationally representative surveys; and associated relative risk data from published, large-scale analyses or meta-analyses.
An estimated 42% of cancer cases in 2014 included in the researchers' sample—659,640 out of the 1,570,975 cancer cases—were linked to the potentially modifiable factors studied. Those factors were linked to an estimated 45.1%, or 265,150 of 587,521, cancer deaths.
Further, the researchers wrote that their results "may underestimate the overall proportion of cancers attributable to modifiable factors, because the impact of all established risk factors could not be quantified, and many likely modifiable risk factors are not yet firmly established as causal."
The researchers found that cigarette smoking made up the greatest share of cancer cases and deaths. Cigarette smoking accounted for 19% of cases and 28.8% of cancer deaths. The second-leading lifestyle factor tied to cancer incidence was excess body weight, which accounted for 7.8% of cases and 6.5% of deaths, followed by alcohol intake, which accounted for 5.6% of cases and 4.0% of deaths.
Lung cancer had the highest number of cases and deaths potentially attributable to preventable factors, according to the researchers, followed by colorectal cancer.
According to the researchers, cancer cases and deaths associated with certain factors were more common among men. Those factors included smoking, red and processed meat consumption, hepatitis C infection, HIV infection, and UV radiation exposure. By contrast, cancer cases and deaths tied to excess body weight, alcohol consumption, physical inactivity, and HPV were more common among women.
The authors wrote, "These findings underscore the vast potential for reducing cancer morbidity and mortality through broad and equitable implementation of known preventive measures." However, they also acknowledged that "many likely modifiable risk factors are not yet firmly established as causal."
Separately, Farhad Islami, a co-author on the study and strategic director of Cancer Surveillance Research at the ACS, said that while the study does not break new ground, it adds to the evidence that prevention can play a big role in reducing cancer prevalence. Experts estimate that 1.6 million new cancer cases will be diagnosed in 2017 and that 600,000 individuals will die from cancer.
Further, Islami said he hopes the findings encourage policymakers at all levels to support policies that reduce modifiable risk factors. Such policies could include creating smoke-free areas and building communities that encourage walking. Physicians can also learn from the findings, Islami said, noting that individuals are more likely to change their behavior when doctors describe the risks to them.
Elizabeth Platz—deputy chair of epidemiology at the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study—called the study "an incredibly important piece of research because it is relevant to understanding cancer risk factors." She added, "It furthers the point that primary prevention is the future. It would be better for everyone to prevent cancer upfront."
In addition, Platz said the findings about body weight are timely. "The obesity epidemic started in the 1980s; it then plateaued but now seems to be on the rise again" (Monga, ABC News, 11/21; Bankhead, MedPage Today, 11/21; Park, Time, 11/21; Islami et al., CA: A Cancer Journal for Clinicians, 11/21).
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