More than one in three cancers could be prevented with simple lifestyle habits changes, a major study suggests.
In one of the first studies of its kind, researchers, analyzed 19 million cases of 36 different cancer types in nearly 200 countries, including the US and UK.
Using 2022 figures, the latest available, the team found 38 percent, or 7.1 million diagnoses, were attributable to 30 modifiable risk factors.
Despite consistent declines in smoking rates across the world, tobacco smoking was the leading modifiable risk factor for cancer, accounting for one in six cases. It was also the top preventable risk factor in men.
Infections, including the sexually transmitted infection human papillomavirus (HPV), a leading cause of cervical and anal cancer, which can be prevented with vaccination and safe sex practices, were linked to one in 10 cancer cases and were the top causes for women, while alcohol was responsible for three percent.
The team also found that lung, stomach and cervical cancers made up nearly half of all preventable cancer cases.
Other risk factors included suboptimal breastfeeding, pollution, lack of exercise and chemicals like asbestos.
The researchers said the findings signal a growing need to look at risk factors for cancer that can be changed, such as smoking, drinking and diet, to help prevent the disease.
A major study has found that one in three cancer cases across the world could be due to preventable factors (stock image)
The above graph shows which specific risk factors were most prominent in each region, divided by sex
The findings come after a report released by the American Cancer Society last month found cancer survival in the US is now higher than ever, with seven in 10 patients living at least five years after their diagnosis.
This is up from 64 percent in 2000 and around 50 percent in the 1970s.
However, some forms of cancer are still on the rise in the US, particularly among young people. Separate recent research from the American Cancer Society found that out of eight forms of cancer, deaths decreased in people under 50 in all except colorectal cancer.
Breast cancer is also on the rise among American women under 50. Recent estimates show from 2004 to 2021, cases in patients ages 20 to 39 rose nearly three percent, a rate more than double the increase seen in women in their 70s.
Scientists are still untangling the reasons behind these cancers rising in young people, but they have largely honed in on lifestyle factors such as diets high in ultra-processed foods, alcohol consumption, obesity and exposure to environmental pollutants.
The new study, published Tuesday in the journal Nature Medicine, looked at rates of 36 different cancers divided by age, sex and country as of 2022. The data was obtained from the GLOBOCAN database, a network run by the International Agency for Research on Cancer (IARC), and included 185 countries.
The team analyzed 30 modifiable risk factors, including smoking, alcohol use, body mass index (BMI), pollution and infections, among others.
The researchers found that in 2022, there were 18.7 million cancer diagnoses worldwide in 2022. Of those, 7.1 million, or 38 percent, were attributed to modifiable risk factors overall.
When looking at sex, 2.7 million or 30 percent of new cancer cases in women were tied to modifiable risk factors compared to 4.3 million of 45 percent for men.
The highest cancer burden tied to modifiable risk factors for women was in sub-Saharan Africa, where 38 percent of new cancers diagnoses are tied to these factors. In North America, 34 percent of cases in women were deemed potentially preventable.
Erin Verscheure was 18 when she was diagnosed with stage four colorectal cancer. It was 2016 and she had just graduated high school when she noticed blood in her stool
The above graph shows the percentages of cancers that can be attributed to modifiable risk factors by region
For men, East Asia had the largest burden of potentially preventable cancers with 57 percent being tied to modifiable risk factors. About one in three cases in North American men with these criteria.
In women, the leading modifiable cause of cancer worldwide was infection, accounting for 11.5 percent of new cases. Infections included HPV, hepatitis, Epstein-Barr and Helicobacter pylori (H pylori).
HPV is a sexually transmitted infection that affects 40 percent of Americans at any given time, and more than 90 percent acquire it at some point in their lifetime. It’s also responsible for nine in 10 cervical and anal cancers.
While the HPV vaccine can prevent about 90 percent of infections, the shot wasn’t rolled out in the US until 2006 and was only recommended for girls and women ages nine to 26. It is also given much less often in developing nations.
HPV can also lie dormant for decades, which can increase the risk of cancer later in life.
Hepatitis has been associated with an increased risk of liver, pancreatic, gastric, oral and thyroid cancers, as well as non-Hodgkin lymphoma, while research has tied Epstein-Barr to lymphoma and some forms of stomach cancer. H Pylori, meanwhile is the leading cause of stomach cancer, even decades after initial infection.
Other leading causes for women were smoking, making up 6.3 percent of cases, and a high BMI, accounting for 3.4 percent of diagnoses.
In the US, Canada and UK, the leading modifiable cancer risk factor was tobacco smoking. Smoking is the cause of nine in 10 lung cancers in the US, as tobacco is a known carcinogen.
Holly McCabe was diagnosed with triple-negative breast cancer at 30 years old after finding a lump in her breast
The above graph shows how specific modifiable risk factors attributed to cancer based on the region
However, smoking rates in the US have decreased dramatically. From 1965 to 2022, rates fell 73 percent among adults, according to the American Lung Association, from 43 percent to 12 percent. And in the last five years, 17 percent fewer adults are smoking.
Tobacco use has also been tied to colorectal cancer, which is surging in young Americans, from 8.6 cases per 100,000 people in 1999 to 13 cases per 100,000 people in 2018, past studies have shown.
Since 2004, incidence among people under 50, a population historically thought of as unlikely to develop the disease, has increased by about two percent every year.
In men, smoking is the leading modifiable cause of cancer worldwide and in the US. It was tied to 23 percent of cases, followed by infections at 9.1 percent and alcohol consumption at 4.6 percent.
The team also found that for women, nearly half a million lung cancers were preventable, with 60.5 percent due to smoking, 27.5 percent caused by pollution and 12 percent influenced by other occupational hazards, including asbestos, arsenic and benzene.
In men, 1.3 million lung cancer cases were from modifiable risk factors. The team found 69 percent were from smoking, 16 percent were from pollution and 15 percent were due to occupational hazards.
The team also tied 33 percent of breast cancers to lack of exercise, 29 percent to a high BMI and 18 percent to suboptimal breastfeeding, as breastfeeding has been shown to shed damaged cells and lower estrogen exposure, which can fuel some breast cancers.
There were several limitations to the study, including looking at uneven data across regions and confirming exact levels of exposure.