The incidence of cancers diagnosed before the age of 50 has dramatically increased around the world, with this rise beginning around 1990, according to a study.
These early onset cancers include cancers of the breast, colon, esophagus, kidney, liver, and pancreas among others, the researchers said.
Possible risk factors for early-onset cancer include alcohol consumption, sleep deprivation, smoking, obesity, and eating highly processed foods, the researchers said.
While adult sleep duration has not drastically changed over the several decades, children are getting far less sleep today than they were decades ago, they said.
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.
"From our data, we observed something called the birth cohort effect," said Shuji Ogino, a professor at the Brigham and Women's Hospital, US.
"This effect shows that each successive group of people born at a later time (e.g., 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," Ogino said.
The study, published recently in the journal Nature Reviews Clinical Oncology, found that the risk is increasing with each generation.
For instance, people born in 1960 experienced higher cancer risk before they turn 50 than people born in 1950.
The researchers predict that this risk level will continue to climb in successive generations.
They first analysed global data describing the incidence of 14 different cancer types that showed increased incidence in adults before age 50 from 2000 to 2012.
The team then searched for available studies that examined trends of possible risk factors including early life exposures in the general populations.
The researchers 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.
They hypothesised that factors like the 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 programs.
The researchers 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.