A substantial number of cancer cases and deaths among adults over 30 in the United States are linked to modifiable risk factors such as smoking and excess body weight, according to a new study published in the American Cancer Society’s journal, CA: A Cancer Journal for Clinicians.
Researchers analyzed data from 2019, excluding non-melanoma skin cancer, to assess the impact of modifiable risk factors on various cancer types. They found that out of 1,781,649 cancer cases, 713,340—approximately 40%—were attributable to factors individuals could potentially control. Similarly, about 44% of cancer deaths, totaling around 262,000, were connected to these risk factors.
Lead study author Dr. Farhad Islami, Senior Scientific Director of Cancer Disparity Research at the American Cancer Society, described the findings as “staggering,” despite previous research already establishing the link between cancer and modifiable risk factors.
Key Modifiable Risk Factors
The study identified smoking as the leading contributor to cancer cases, despite a decline in cigarette-associated cancer due to reduced smoking rates. Smoking was responsible for 19% of cancer cases and nearly 29% of cancer-related deaths. Lung cancer, in particular, was significantly linked to smoking, with smokers having a 25 times higher risk of developing lung cancer compared to non-smokers.
Excess body weight was the second most significant factor, accounting for almost 8% of cancer cases. Other notable risk factors included alcohol consumption (5%), exposure to ultraviolet (UV) rays (almost 5%), and physical inactivity (3%).
Lung cancer topped the list of smoking-related cancers, but smoking also increased the risk of cancers such as urinary bladder, colorectal, and oral cavity cancers. Excess body weight and alcohol consumption each contributed to over 7% and 5% of cancer cases and deaths, respectively. A combination of excess weight, alcohol consumption, physical inactivity, and poor diet was linked to 17% of cancer deaths.
Gender and Ethnicity Disparities
The study highlighted that breast, endometrial, and cervical cancers among women were significantly linked to these risk factors. HPV infections, preventable through vaccination, were also associated with these cancers. Female breast cancer followed lung cancer in the number of cases linked to elevated risk factors, with almost 84,000 cases in 2019. Skin melanoma and colorectal cancer followed with nearly 83,000 and over 78,000 cases, respectively.
Public Awareness and Prevention
Despite clear evidence, many people remain unaware of how factors like alcohol consumption, lack of exercise, and poor diet contribute to cancer risk. A 2019 survey by the American Institute for Cancer Research found that many are surprised to learn that “energy imbalance”—where caloric intake exceeds energy expenditure—can lead to cancer.
Dr. Otis Brawley, an oncologist and epidemiologist at Johns Hopkins University, emphasized that energy imbalance, incorporating obesity, poor diet, and lack of exercise, is the second leading cause of cancer in the U.S. and is poised to become the leading cause.
Recommendations to Reduce Cancer Risk
To mitigate cancer risk, Dr. Islami recommends quitting smoking, maintaining a healthy weight, following healthy eating guidelines, and staying physically active. The CDC advises 150 minutes of moderate aerobic activity weekly and muscle-strengthening activities at least twice a week. Even small amounts of exercise, such as 11 minutes of vigorous activity daily, can significantly reduce cancer risk.
Avoiding alcohol or limiting consumption to two drinks per day for men and one for women is also advised. Additionally, protecting against UV exposure by staying in the shade, using sunscreen with SPF 30 or higher, and avoiding indoor tanning can reduce cancer risk. Vaccinations for hepatitis B and HPV are also effective preventive measures.
Dr. Timothy Rebbeck from the Dana-Farber Cancer Institute highlighted the importance of public education on cancer prevention, stressing that individuals can take impactful steps to reduce their cancer risk through lifestyle modifications. Engaging with healthcare providers for personalized strategies can help individuals address specific risk factors and adopt healthier habits.
