CNN -- About 40% of new cancer cases among adults ages 30 and older in the United States - and nearly half of deaths - could be attributed to preventable risk factors, according to a new study from the American Cancer Society. "These are things that people can practically change how they live every single day to reduce their risk of cancer," said Dr. Arif Kamal, chief patient officer with the American Cancer Society.
Smoking was the leading risk factor by far, the study found, contributing to nearly 1 in 5 cancer cases and nearly a third of cancer deaths. Other key risk factors included excess body weight, alcohol consumption, physical inactivity, diet and infections such as HPV. Overall, researchers analyzed 18 modifiable risk factors across 30 types of cancer.
In 2019, these lifestyle factors were linked to more than 700,000 new cancer cases and more than 262,000 deaths, the study found. Cancer grows because of DNA damage or because it has a fuel source, Kamal said. Other things - such as genetics or environmental factors - can also create these biological conditions, but modifiable risks explain a significantly larger share of cancer cases and deaths than any other known factors.
Exposure to sunlight can damage DNA and lead to skin cancer, for example, while fat cells produce hormones that can feed certain cancers. "With cancer, it oftentimes feels like you have no control," Kamal said. "People think about bad luck or bad genetics, but people need to feel a sense of contro.