Obesity-related cancer rates among US young adults see steep rise, Lancet reports

04 Feb 2019 --- Incidence rates are increasing for 6 out of 12 obesity-related cancers among US young adults, with steeper increases seen in younger ages and successively younger generations. This is according to a study published in The Lancet Public Health. The study also looked at rates of 18 cancers unrelated to obesity and found increasing rates in only two. These findings present a potentially worrying future for the health of young adults in the US as they age, according to the researchers. Therefore, they are calling for policy implementation to help tackle the issue, with specific reference to obesity.

“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,” says Dr. Ahmedin Jemal, senior/corresponding author of the study.

Previously, the authors of the study had identified increases in early onset colorectal cancer in the US, a trend that has been observed in several high-income countries and could partly reflect the obesity epidemic. They extended that analysis by examining recent age-specific trends in 30 types of cancers, including 12 known to be associated with obesity.

The team, led by Dr. Hyuna Sung, examined 20 years of incidence data, from 1995 to 2014, for 30 cancers across 25 states. The North American Association of Central Cancer Registries provided the data, which covered 67 percent of the US population. This is the first study to systematically examine incidence trends for obesity-related cancers in US young adults, according to the researchers.

Out of the 12 obesity-related cancers that the team examined, incidence increased for six of them, including colorectal, uterine corpus or endometrial, gallbladder, kidney, multiple myeloma and pancreatic cancer. Incidence was found to increase in young adults and in successively younger birth cohorts in a stepwise manner. This means that the risk of these six cancers is double the rate that baby boomers had at the same age. 

By contrast, the researchers found that rates in successive younger birth cohorts declined or stabilized in all but 2 of 18 other, non-obesity related cancers, including smoking-related and infection-related cancers. Further supporting this, the American Cancer Society recently released a report on the 25 years of declining cancer rates that were heavily influenced by the declining smoking culture.

“Although the absolute risk of these cancers is small in younger adults, these findings have important public health implications,” notes Dr.Jemal. 

The researchers call for policymakers and health care providers to implement innovative strategies, in order to mitigate morbidity and premature mortality relating to obesity.

“Cancer trends in young adults often serve as a sentinel for the future disease burden in older adults, among whom most cancer occurs,” Dr. Jemal warns.

Recently an American Cancer Society peer-reviewed study found that excess body weight was responsible for roughly 4 percent of cancers worldwide in 2012, with the percentage expected to rise. The report said that calorific, nutrient-poor food and physically inactive lifestyles are driving up the percentage of overweight people worldwide and promoting noncommunicable diseases, including cancer. By contrast, smoking and infection-related cancers, have reached a plateau or decreased in prevalence.