BOSTON — Over the past three decades, a troubling trend has emerged regarding cancer diagnosis rates on a global scale. More and more adults under the age of 50 are developing various forms of cancer. Scientists at Brigham and Women’s Hospital report the incidence of early onset cancers (cancers detected in individuals younger than 50) all over the world has increased “dramatically” since around 1990.
More specifically, cancers of the breast, colon, esophagus, kidney, liver, and pancreas have all seen upticks in early onset diagnoses.
In an effort to better understand why this is happening, study authors conducted an extensive set of analyses using data gathered from various sources, including information pertaining to early life encounters that may have influenced this trend.
“From our data, we observed something called the birth cohort effect. 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,” says Shuji Ogino, MD, PhD, a professor and physician-scientist in the Department of Pathology at the Brigham, in a media release. “We found that this 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 and we predict that this risk level will continue to climb in successive generations.”
Are doctors simply catching more cancers?
To start, researchers analyzed global data encompassing the incidence of 14 different cancer types. That analysis indicated increased incidence among adults before the age of 50 from 2000 to 2012. Next, the research team searched for any additional studies focusing on trends of possible risk factors, such as early life exposures in general populations. The team then compared any and all pertinent literature describing clinical and biological tumor characteristics of early onset cancers to later onset cancer cases diagnosed after the age of 50.
This extensive review led researchers to the sobering conclusion that the early life exposome — which refers to an individual’s diet, lifestyle, weight, environmental exposures, and microbiome — has changed substantially over the past few decades. As far as why this is happening, researchers theorize that factors like the westernized diet and lifestyle are likely major contributors to the early-onset cancer epidemic.
However, study authors also note that at least some of the observed increase in global early onset cancer diagnoses is possibly due to improved early detection methods in cancer screening programs. Researchers can’t say at this time what proportion of cancer diagnoses could solely be the result of better screening and early detection, but they are confident that enhanced screening is far from the only factor at play here.
What’s changing over the last 30 years?
Risk factors usually associated with early onset cancer include alcohol habits, sleep deprivation, smoking, obesity, and eating highly processed foods. Interestingly, study authors did not observe any notable changes in adult sleep habits over the past three decades, but children are getting much less sleep today than they were decades ago. Many risk factors, such as consuming highly processed foods and sugary beverages, obesity, type 2 diabetes, a sedentary lifestyle, and alcohol consumption have all increased significantly in the general population since the 1950s.
“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,” explains lead study author Tomotaka Ugai, MD, PhD. “Diet directly affects microbiome composition and eventually these changes can influence disease risk and outcomes.”
Study authors add that their research was limited by a lack of adequate data pertaining to low and middle-income countries. It’s also imperative that future long-term studies include young children and track their health outcomes for at least a few decades.
“Without such studies, it’s difficult to identify what someone having cancer now did decades ago or when one was a child,” Dr. Ugai explains, “Because of this challenge, we aim to run more longitudinal cohort studies in the future where we follow the same cohort of participants over the course of their lives, collecting health data, potentially from electronic health records, and biospecimen at set time points. This is not only more cost effective considering the many cancer types needed to be studied, but I believe it will yield us more accurate insights into cancer risk for generations to come.”
The study is published in the journal Nature Reviews Clinical Oncology.