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Millennials Are Getting More Obesity-Related Cancers Than Baby Boomers
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Millennials Are Getting More Obesity-Related Cancers Than Baby Boomers

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Obesity-related cancers usually seen in the elderly are rising at a faster rate in millennials than in older generations in the United States, according to a study published Monday in the journal The Lancet Public Health to coincide with World Cancer Day.

The obesity epidemic may be contributing to an increase in certain cancers among millennials in the U.S., a new study suggests. According to a statement from the authors, the study is the first to systematically examine trends in obesity-related cancers in young adults in the U.S.

A team from the American Cancer Society, led by Hyuna Sung, analyzed cancer rates from 25 U.S. state cancer registries (covering 67% of the U.S. population) diagnosed from 1995 to 2014. They examined the rates of 30 different cancers, including the 12 obesity-related cancers, as well as 18 other cancers not typically associated with obesity, such as lung and skin cancer.

Using the Cancer in North America database, the researchers collected information on these 30 types in patients aged 25-84 who were diagnosed between January 1, 1995, and December 31, 2014.

Overall, they documented 14,672,409 cases of these 30 cancers during that period, finding that the incidence of 6 of the 12 obesity-related types (colorectal, uterine corpus, gallbladder, kidney, pancreatic and a type of blood cancer known as multiple myeloma) rose significantly in adults between the ages of 25 and 49.

Although rates of most of these cancers also rose in older adults, the increases were much smaller.

For example, the incidence of pancreatic cancer among those aged 45-49 increased by 0.77% compared to a rise of 2.47% for ages 30-34 and 4.34% for the group aged 25-29.

“The annual percent change by age was largest in individuals aged 25–29 years for cancers of the kidney, gallbladder, corpus uteri, and colorectum, and in individuals aged 30–34 years for multiple myeloma,” the authors wrote in the study.

“The risk of cancer is increasing in young adults for half of the obesity-related cancers, with the increase steeper in progressively younger ages,” co-author Ahmedin Jemal, vice president of Surveillance and Health Services Research for the American Cancer Society, told CNN. “Although the absolute risk of these cancers is small in younger adults, these findings have important public health implications. The future burden of these cancers could worsen as younger cohorts age, potentially halting or reversing the progress achieved in reducing cancer mortality over the past several decades.”

According to the researchers, the growing obesity epidemic in the United States could be influencing the trends identified in the study. 

They cite figures which show that the prevalence of obesity or being overweight increased by more than 100% (from 14.7% to 33.4%) between 1980 and 2014 among U.S. children and adolescents. Furthermore, it rose by 60% among adults aged 20–74 years (from 48.5% to 78.2%).

“In adults aged 30 years and older in the USA, excess body weight could account for up to 60% of all endometrial cancers, 36% of gallbladder cancers, 33% of kidney cancers, 17% of pancreatic cancers, and 11% of multiple myelomas in 2014,” the report said.

“Given the large increase in the prevalence of overweight and obesity among young people and increasing risks of obesity-related cancers in contemporary birth cohorts, the future burden of these cancers could worsen as younger cohorts age, potentially halting or reversing the progress achieved in reducing cancer mortality over the past several decades. Cancer trends in young adults often serve as a sentinel for the future disease burden in older adults, among whom most cancer occurs,” Jemal said in a statement.

“Excess body weight is a known carcinogen, associated with more than a dozen cancers and suspected in several more,” the study authors wrote. “Growing evidence supports an association between childhood or adolescent obesity and increased risk of colorectal, endometrial, and pancreatic cancers and multiple myeloma.”

The picture is very different when looking at the 18 other non-obesity-related cancer types: Incidences increased in successively younger generations for only two of these, while it decreased in about half of them (particularly those related to smoking or HIV infection.)

“Younger generations are experiencing earlier and longer-lasting exposure to excess fat and to obesity-related health conditions that can increase cancer risk,” Jemal said.

Research isn’t definitive on how exactly obesity is linked to cancer, but numerous studies have linked lower body weight to less cancer risk, and side effects of obesity to certain types of cancer. Obese people are known to have chronic low-level inflammation, which can, over time, cause DNA damage that leads to cancer. Obesity increases the risk of gallstones, which are strongly associated with a higher risk of gallbladder cancer. Fat tissue produces excess estrogen, high levels of which have been associated with increased risks of breast, endometrial, and ovarian cancer.

In 2016, the International Agency for Research on Cancer (a branch of the World Health Organization) published a report linking obesity to a higher risk of 12 cancers, Live Science notes.

The National Institute of Diabetes and Digestive Diseases reports that two in three U.S. adults are considered to be overweight or obese. A poor diet high in processed food, and low exercise rates have contributed to the obesity epidemic among millenials.

Researchers conclude that their findings have significant public health implications, particularly for health care providers and policy makers, and provide a stepping stone for future research on the relationship between the obesity epidemic and early onset cancer.

They also noted that their study found only an association between obesity and cancer, and cannot prove that obesity causes these cancers. Nor can it prove that the obesity epidemic is responsible for the increases in cancer rates in young adults.

As the BBC points out, obesity is only one factor — the environment, genetics and other issues also play roles. Not everyone who gets these cancers is overweight either, and not everyone who is obese will necessarily get these cancers.

Despite the findings, it’s not all bad news on the cancer front: The study shows that rates have declined or stabilized in all but two of 18 non-obesity related cancers, including smoking-related and infection-related cancers.

Author: USA Really