Increasing Myeloma and Other Cancer Incidence in Younger Adults Points to Obesity Epidemic

The incidence of a number of obesity-related cancers appeared to gradually increase in young adults compared with the declining or stabilized trends found in smoking- and infection-related cancers, according to study findings published in The Lancet Public Health.

In turn, because the prevalence of being overweight or obesity among young people is increasing, the future burden of obesity-related cancers may worsen as these individuals age, “potentially halting or reversing the progress achieved in reducing cancer mortality over the past several decades,” the researchers wrote.

Obesity rates have doubled between 1980 and 2014, an epidemic that may be linked to rising cancer incidences, including myeloma and colorectal cancer, among younger adults aged 25 and 49.

“Cancer trends in young adults, often under 50 years, reflect recent changes in carcinogenic exposures, which could foreshadow the future overall disease burden,” the researchers wrote. “Previous studies reported an increase in early onset colorectal cancer, which could partly reflect the obesity epidemic.”

The researchers conducted a population-based study of over 14 million cases of invasive cancer in individuals aged 25 to 84, determined by data from 25 state cancer registries and covering 67 percent of the US population between 1995 and 2014. Examining contemporary incidence trends for 30 cancer types, the study considered the 20 most common cancer types and 12 cancers considered to be obesity-related.

They found a significantly higher incidence in younger adults (aged 25 to 49) for six of the 12 cancers considered to be obesity-related — including multiple myeloma, colorectal, uterine corpus, gallbladder, kidney and pancreatic cancer – and reported even higher rates in sequentially younger generations. The findings showed a 1.44 percent annual increase in incidence rate ratios (IRRs) for multiple myeloma for individuals aged 25 to 29 years old, compared with an IRR of 1.59 percent among those born around 1950.

“In adults aged 30 years and older in the USA, excess bodyweight could account for up to… 11% of multiple myelomas in 2014,” the researchers wrote. “Because most epidemiological studies have primarily focused on older populations, the effect of excess bodyweight in early life or of weight change from young adulthood on cancer risk in different stages of the life course is not well characterized. Nevertheless, growing evidence supports an association between childhood or adolescent obesity and increased risk of colorectal, endometrial, and pancreatic cancers and multiple myeloma.”

Thyroid cancer, while also considered to be obesity-related, showed higher occurrences in both younger and older individuals. Only two of the 18 cancers considered to be obesity-related (gastric non-cardia cancer and leukemia) showed an increased incidence in successively younger generations.

“Our finding of increasing incidence in younger generations for some obesity-related cancers has significant practical public health implications, especially for health care providers and policy makers,” the researchers added.