A study by researchers at Brigham and Women’s Hospital finds that the incidence of early-onset cancers – including breast, colon, esophagus, kidney, liver and pancreas – has risen dramatically around the world, with an increase beginning around 1990. In an effort to understand why many more people under the age of 50 are being diagnosed with cancer, scientists have carried out extensive analyzes of available data, including information on early exposures that may have contribute to this trend. The results are published in Nature Reviews Clinical Oncology.
“From our data, we observed what is called the birth cohort effect. This effect shows that each successive group of people born later – say, a decade later – has a higher risk of developing cancer later in life, likely due to risk factors they were exposed to in a young age,” Shuji Ogino said. , professor at Harvard Chan School and Harvard Medical School and physician-scientist in the Department of Pathology at Brigham. “We found that this risk increases with each generation. For example, people born in 1960 had a higher cancer risk before they turned 50 than people born in 1950, and we expect this level of risk to continue to increase over generations.
Ogino worked with lead author Tomotaka Ugai and colleagues from 2000 to 2012 to analyze global data on 14 types of cancer that showed increased incidence in adults before age 50. Next, the team searched for available studies that looked at trends in possible risk factors, including early exposures. in the general population. Finally, the researchers reviewed the literature describing the clinical and biological tumor characteristics of early-onset cancers compared with cancers diagnosed after age 50.
In an in-depth examination, the team found that the “exposome” of early life, which encompasses an individual’s diet, lifestyle, weight, environmental exposures and microbiome, has changed dramatically. over the past decades. They hypothesize that factors such as Western diet and lifestyle could contribute to the increase in early cancers. The team recognized that this increased incidence of certain types of cancer is, in part, due to early detection through cancer screening programs. They could not accurately measure how much of this growing prevalence could be attributed solely to screening and early detection. However, they noted that an increase in the incidence of many of the 14 cancer types is unlikely due to improved screening alone.
Possible risk factors for early cancer included alcohol consumption, sleep deprivation, smoking, obesity, and consumption of highly processed foods. Surprisingly, researchers have found that while adults’ sleep duration hasn’t changed drastically over the decades, children sleep much less today than they did decades ago. Risk factors such as highly processed foods, sugary drinks, obesity, type 2 diabetes, physical inactivity and alcohol consumption have all increased dramatically since the 1950s.
“Of the 14 types of rising cancers we studied, eight were related to the digestive system. The food we eat feeds the microorganisms in our gut,” Ugai said. “Diet directly affects the composition of the microbiome, and possibly these changes can influence disease risk and outcome.”
One of the limitations of this study is that the researchers did not have enough data from low- and middle-income countries to identify trends in cancer incidence over decades. In the future, 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 can be followed for several decades.
“Without such studies, it is difficult to identify what a person with cancer did decades ago or when one was a child,” Ugai said. “Because of this challenge, we aim to conduct more longitudinal cohort studies in the future where we follow the same cohort of participants over their lifetime, collecting health data, potentially from health records. electronic health, and biological samples at specific times. This is not only more cost effective given the many types of cancer to be studied, but I believe it will give us more accurate information about cancer risk for generations to come.
Ogino’s work is supported in part by grants from the US National Institutes of Health and the Cancer Grand Challenge Award from Cancer Research UK. Ugai’s work is supported by grants from the Prevent Cancer Foundation, the Japan Society for the Promotion of Science, and the Mishima Kaiun Memorial Foundation.
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