Half of all cancers are caused by six lifestyle factors — study finds

Almost half of cancer deaths can be attributed to six decisions people make in their everyday life.

According to a new report, which was published the American Cancer Society, four in 10 cancer cases and nearly half of cancer deaths over 30 are linked to smoking cigarettes, being overweight, using alcohol, being inactive, eating a poor diet and getting too much sun.

Other factors, like secondhand smoke exposure, eating red meat, having unprotected sex, leading to HPV or HIV infection and a diet low in calcium, were also identified as the cause for a number of cancer cases, but caused a fraction of the cases compared to the top six categories.

Despite anti-smoking campaigns and declining tobacco trends, cigarettes were still the biggest contributor to cancer cases – accounting for 20 per cent of all new cancer cases and 30 per cent of all cancer deaths in 2019.

“The number of lung cancer deaths attributable to cigarette smoking is alarming,” Dr Farhad Islami, the study author and the senior scientific director of cancer disparity research at the American Cancer Society, said.

Following cigarettes, the largest number of cancers were attributed to excess body weight, alcohol consumption, sun damage and physical inactivity.

The authors didn’t define excess body weight, but it’s likely that they were relying on body mass index, a standard used by U.S. doctors, which places patients into four categories based on their height and weight: underweight, normal weight, overweight and obese.

Excess body weight could encompass people in both the overweight and obese categories, or it could just include obese people.

The researchers also didn’t specify the amounts of alcohol consumed by the people included in the study. However, the US Centers for Disease Control defines regular alcohol use as two drinks per day for men and one drink per day for women.

However, they recommend drinking less, and say that the safest bet is to avoid drinking all together.

Dr Islami said the results highlighted the importance of educating about the importance of quitting smoking and getting appropriate nutrition and exercise.

‘Interventions to help maintain healthy body weight and diet can also substantially reduce the number of cancer cases and deaths in the country,’ Dr Islami said.

Roughly seven in ten Americans are obese or overweight, according to the NIH, a number which has been steadily rising since the 1970s.

Doctors think that excess fat in the body alters how your body regulates hormones and inflammation, which can lead to increased cancer risk by changing the natural life cycle of cells, Dr Karen Basen-Engquist, a professor in Behavioral Science at MD Anderson who was not involved in the study, said.

This leads to an increased risk for colorectal, breast, uterine, esophageal, kidney and pancreatic cancer.

In 2019, there were 713,340 cancer cases diagnosed in Americans over 30, and 262,120 cancer deaths, according to the report, which was published in CA: A Cancer Journal for Clinicians.

Nineteen per cent of the new diagnoses, which represented 344,070 people, were attributable to cigarette smoking.

Thirty per cent of the deaths, which represented roughly 169,810, were caused by cigarette smoking.

Excess body weight was responsible for 135,910 new cases and 43,520 deaths in people over 30 in 2019.

Alcohol use was responsible for 96,730 new cases and 24,410 deaths in people over 30 in 2019.

Falling close behind were cancers caused by sedentary lifestyle, poor diet, sun exposure, and infections with the human papilloma virus (HPV).

HPV is a sexually transmitted disease linked to cervical, throat, mouth and anal cancer, and it caused more cancers than factors like eating a diet high in processed meat, the study found.

The disease is commonly spread through unprotected vaginal, anal and oral sex.

This revealed a ‘continued need’ to raise awareness about the HPV vaccine, which is highly effective at preventing against the STI, study author Dr Ahmedin Jemal.

“Vaccination at the recommended time can substantially reduce the risk of chronic infection, and consequently, cancers associated with these viruses,” Dr Jemal, senior vice president of surveillance and health equity science at the American Cancer Society, said.

Not every type of cancer is easily attributable to risk factors like those laid out in the study. As such, the researchers focused on those with a clear link to behaviors – like lung cancer, melanoma and colorectal cancer.

To arrive at these conclusions, researchers didn’t take a poll of every American household.

Instead, they used data available from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program, which tracks national cancer cases.

The report highlighted the importance of raising awareness about these risk factors, and said that it’s still possible to begin educating people and ‘substantially reduce’ cancer cases and deaths in the country.