Why cancers in under-50 adults are increasing globally, by scientists
• Red flags on alcohol, sleep deprivation, smoking, obesity, processed foods
A study, published, yesterday, has provided reasons why, in recent decades, more adults under the age of 50 are developing cancer.
Conducted by researchers from Brigham and Women’s Hospital, Boston, Massachusetts, United States (U.S.), the study revealed that early onset (those diagnosed before age 50), including cancers of the breast, colon, oesophagus, kidney, liver, and pancreas, among others, dramatically increased worldwide, beginning around 1990.
The study was published in Nature Reviews Clinical Oncology. A professor and physician-scientist in the Department of Pathology at Brigham, Shuji Ogino, said: “From our data, we observed something called the birth cohort effect. This shows that each successive group of people born at a later time (example, decade-later) have a higher risk of developing cancer later in life, likely due to risk factors they were exposed to at a young age.
“We found that this risk is increasing with each generation. For instance, people born in 1960 experienced higher cancer risk before they turned 50 than people born in 1950, and we predict that this risk level will continue to climb in successive generations.”
To conduct this study, Ogino and lead author, Dr. Tomotaka Ugai, also of the Department of Pathology, and their colleagues, first analysed global data describing 14 different cancer types that showed increased incidence in adults before age 50, from 2000 to 2012.
Then, the team searched for available studies that examined trends of possible risk factors, including early life exposures in the general populations.
Finally, the team examined the literature describing clinical and biological tumour characteristics of early-onset cancers, compared to later-onset cancers diagnosed after age 50.
In an extensive review, the team found that the early life exposome, which encompasses one’s diet, lifestyle, weight, environmental exposures, and microbiome, has changed substantially in the last several decades.
Thus, they hypothesised that factors, like westernised diet and lifestyle, may be contributing to the early-onset cancer epidemic.
The team acknowledged that this increased incidence of certain cancer types is, in part, due to early detection through cancer screening programmes. They couldn’t precisely measure what proportion of this growing prevalence could solely be attributed to screening and early detection. However, they noted that increased incidence of many of the 14 cancer types is unlikely solely due to enhanced screening alone.
Possible risk factors for early-onset cancer included alcohol consumption, sleep deprivation, smoking, obesity, and eating foods. Surprisingly, researchers found that while adult sleep duration hasn’t drastically changed over several decades, children are getting far less sleep today than they were decades ago.
Risk factors such as highly-processed foods, sugary beverages, obesity, type 2 diabetes, sedentary lifestyle, and alcohol consumption have all significantly increased since the 1950s, which researchers speculate has accompanied altered microbiome.
“Among the 14 cancer types on the rise that we studied, eight were related to the digestive system. The food we eat feeds the microorganisms in our gut,” said Ugai. “Diet directly affects microbiome composition and eventually, these changes can influence disease risk and outcomes.”
One limitation of this study is that researchers did not have an adequate amount of data from low- and middle-income countries to identify trends in cancer incidence over the decades.
Going forward, Ogino and Ugai hope to continue this research by collecting more data and collaborating with international research institutes to better monitor global trends.
They also explained the importance of conducting longitudinal cohort studies with parental consent to include young children who may be followed up for several decades.