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Why under-50s cancer is rising – US review

Lifestyle factors beginning in adolescence and young adulthood are possible risk factors for the increasing cases of early-onset cancers, which occur before the age of 50, say researchers, adding that longitudinal studies are needed to confirm their results.

Cancer is the second leading cause of death worldwide, and while it typically affects people 50 and older, studies indicate that, since the 1990s, certain cancers have been rising among those under 50 in many parts of the world.

Early-onset cancers pose a higher risk of long-term health problems, including infertility, cardiovascular conditions, as well as side-effects from treatment.

A recent review of various studies to determine possible risk factors for this found that lifestyle factors early in life, such as diet, obesity, and environmental exposure, might contribute to early onset cancer risk, reports MedicalNewsToday.

For the review, the researchers first analysed global data from the years 2000 to 2012 on the incidence of 14 cancer types that have increased among adults under 50. These included: breast, colorectal, endometrial, oesophageal, head and neck, kidney, multiple myeloma, pancreatic, prostate, stomach and thyroid cancer.

They then examined studies investigating possible risk factors, alongside literature describing the clinical and biological tumour characteristics of early and later-onset cancers.

They acknowledged that the increased incidence of early-onset cancer might be partially linked to increased screening uptake. They also wrote, however, that other factors might be responsible, too.

Lifestyle factors and cancer risk

After analysing the literature, they noted that increasing evidence suggests that there might be intervals of several decades between initial cellular damage and clinical cancer detection. They also found increases in early-onset cancer correlate with rising lifestyle trends, including more westernised diets, lifestylesi and environments.

Such changes, they added, which started in the mid-20th century, might have affected the incidence of early-onset cancer from the 1990s as their effects would have taken time to accumulate.

Lifestyle factors that may increase cancer risk include:

Westernised diet, defined as high in saturated fats, red meat, processed meat, sugar and ultra-processed foods yet low in fruits, vegetables, whole grains and fibre;
Lower breastfeeding rates and increased formula milk consumption;
Increased alcohol consumption;
Smoking habits, including personal habits and second-hand smoke or in-utero exposure;
Reduced sleep among children due to bright lights during the night;
Night shift work, which increases cancer risk factors such as obesity and diabetes;
Reproductive changes, including reduced age of menarche, reduced number of births, increased age at first and last birth, and oral contraceptive use;
Physical inactivity and sedentary lifestyle.

The researchers wrote that eight of the 14 cancers studied relate to the digestive system, indicating the importance of the oral and intestinal microbiome in cancer risk. In particular, they highlighted nutrition, lifestyle factors, and higher antibiotic use as factors affecting the microbiome and increasing cancer risk.

Dr Tomotaka Ugai, research fellow in pathology at Brigham and Women’s Hospital, Harvard Medical School and one of the study’s authors, told MNT that the research had some limitations.

“One is that we did not have adequate data from low- and middle-income countries to identify trends in cancer incidence over the decades. We hope to continue this research by collecting more data and collaborating with international research institutes to better monitor global trends,” he said.

“Another limitation is the paucity of longitudinal cohort studies with data on early-life exposures and biospecimen. We need long-term investments and commitments to such cohort studies.

“This review pulls together a large range of research on multiple risk factors and multiple cancers to give a big picture of these trends. This type of big-picture ecologic look does not prove that these risk factors are causing the increase in cancer. Instead, it suggests an association that mechanistic studies need to explore.

“There have been many individual well-designed longitudinal studies that have provided causal evidence for many of these risk factors on many of these cancers, so there is evidence to support the summarised issues in this review.”

When asked how lifestyle factors might increase early-onset cancer risk, Dr Gypsyamber D’Souza, professor in cancer epidemiology at Johns Hopkins University, who was not involved in the study, told MNT:

“Lifestyle factors such as obesity, physical inactivity and poor diet are associated with increased risk of multiple cancers. Possibly, these factors increase cancer risk both directly and indirectly. For example, they can cause increased inflammation and influence or disrupt cellular regulatory processes thus directly increasing risk, and they can cause other chronic diseases which then, in turn, increase cancer risk.”

Dr Jeanine Genkinger, associate professor of epidemiology at Columbia University, who was not involved in the study, said many of the lifestyle factors linked to early onset cancer risk can also affect cancer risk later in life.

“Various lifestyle factors that the authors highlight also have an impact on later onset cancers. It is just the timeframe within the life-course that may be different to cause early onset cancers. Factors like obesity may impact through insulin resistance, and inflammation to cause cancer risk.

“We know that these lifestyle factors have changed over the past few decades to more unhealthy characteristics at earlier time-points in the life-course. For example, we see higher rates of overweight and obesity in children today compared with 30 years ago, and we also know that children consume higher amounts of sugar-sweetened beverages today than they did 30-40 years ago,” she said.

Study details

Is early-onset cancer an emerging global epidemic? Current evidence and future implications

Tomotaka Ugai, Naoko Sasamoto, Hwa-Young Lee, Mariko Ando, Mingyang Song, Rulla M. Tamimi, Ichiro Kawachi, Peter Campbell, Edward Giovannucci, Elisabete Weiderpass, Timothy Rebbeck & Shuji Ogino.

Published in Clinical Oncology on 6 September 2022


Over the past several decades, the incidence of early-onset cancers, often defined as cancers diagnosed in adults <50 years of age, in the breast, colorectum, endometrium, oesophagus, extrahepatic bile duct, gallbladder, head and neck, kidney, liver, bone marrow, pancreas, prostate, stomach and thyroid has increased in multiple countries. Increased use of screening programmes has contributed to this phenomenon to a certain extent, although a genuine increase in the incidence of early-onset forms of several cancer types also seems to have emerged. Evidence suggests an aetiological role of risk factor exposures in early life and young adulthood. Since the mid-20th century, substantial multigenerational changes in the exposome have occurred (including changes in diet, lifestyle, obesity, environment and the microbiome, all of which might interact with genomic and/or genetic susceptibilities).
However, the effects of individual exposures remain largely unknown. To study early-life exposures and their implications for multiple cancer types will require prospective cohort studies with dedicated biobanking and data collection technologies. Raising awareness among both the public and health-care professionals will also be critical. In this Review, we describe changes in the incidence of early-onset cancers globally and suggest measures that are likely to reduce the burden of cancers and other chronic non-communicable diseases.


MedicalNewsToday article – Why are so many people under 50 getting cancer? (Open access)


Clinical Oncology abstract – Is early-onset cancer an emerging global epidemic? Current evidence and future implications (Open access)


See more from MedicalBrief archives:


Cancer screening – the good, the bad and the ugly


Cancer: Survivability is changing fast


Increased colon cancer risk extends to second- and third-degree relatives


Sugary drinks associated with increased risk of colorectal cancer in women




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