In a review paper published in Nature, scientists discuss the problem of the rising burden of early-onset cancer .
Not just a disease of aging
We tend to think of cancer of a disease of aging, and for a good reason: cancer is indeed highly correlated with age. However, in recent decades, there has been a worrying uptick in cancer in people younger than 50: early-onset cancer. The problem has become so noticeable that the US National Cancer Institute named it a research priority. Its data suggests that cancer incidence in people aged 25-39 can increase by an additional 11%-12% by 2030, and we can only speculate about the causes. In this review, the authors tried to summarize what we know about this phenomenon and provide several ideas as to why it is happening and what can be done about it.
The usual suspects
Some possible reasons, like the obesity epidemic, immediately come to mind. Obesity is a risk factor for multiple types of cancer, including cancers with an increased number of early-onset cases (in their review, the authors mention breast, colorectal, pancreatic, esophageal, endometrial, head and neck, and kidney cancer as well as multiple myeloma). However, it must be noted that the relationship between obesity and breast cancer is more complicated: BMI is negatively associated with survival in early breast cancer, but positively in late breast cancer .
Another risk factor shared by most of these cancers is a sedentary lifestyle, which can also promote obesity. Just like obesity, a lack of physical activity is prevalent among children and young adults, with three out of four American teens, especially girls, not getting enough exercise .
Then, there are unhealthy dietary habits. The so-called Western diet based on heavily processed foods packed with empty calories significantly increases the risk of cancer, both by inducing obesity and on its own.
An unhealthy diet strongly and directly contributes to the risk of colorectal cancer . In addition to obesity and type 2 diabetes, it also promotes inflammatory bowel disease, another risk factor for cancer . Processed meat in particular has been implicated in cancer, and there is also some equivocal evidence about red meat. While meat production growth has almost ground to a halt in Europe and North America, it is skyrocketing in Asia.
This is a good moment to mention that the dynamics of early-onset cancer differ significantly between countries and regions, as do risk factors. For instance, while the West might be slowly weaning itself off its unhealthy diet, many developing countries seem to embrace it due to the decrease in poverty.
Less known factors
Other factors might not be as obvious. For instance, breast cancer has been shown to positively correlate with earlier menarche (first menstruation), use of oral contraceptives, nulliparity (never giving birth), older age at first birth, and never breastfeeding.
Lack of sleep is another risk factor with a high prevalence in school and college students . While there is little hard data on whether sleep patterns have changed in recent decades, one Stanford publication discusses the possible effect of smartphones and tablets.
Not everything is bleak, though. First, early detection is definitely one of the factors behind the rise in cancer cases in people younger than 50; it catches slowly advancing cancers that previously could fly under the radar until older age. Second, smoking, a major risk factor for various types of cancer, is retreating. Same goes for alcohol consumption, although not in all countries and regions.
Paradigm shift needed
The authors advocate for a paradigm shift that includes more awareness of early-onset cancer. This echoes the current state of knowledge in the longevity field. As geroscientists know now, damage to our cells and organs starts accumulating very early, probably even before birth, and not even a young and vigorous organism can offset it completely. For instance, no matter when you quit smoking, previous smoking will remain a risk factor; of course, it’s still a good idea to stop smoking.
This thorough review raises awareness of the growing problem of early-onset cancer, catalogs possible causes, and suggests ways to combat this rising trend. This reinforces the position of the longevity field that fighting aging should start much earlier in life than previously thought.
 Ugai, T., Sasamoto, N., Lee, H. Y., Ando, M., Song, M., Tamimi, R. M., … & Ogino, S. (2022). Is early-onset cancer an emerging global epidemic? Current evidence and future implications. Nature Reviews Clinical Oncology, 1-18.
 Modi, N. D., Tan, J. Q. E., Rowland, A., Koczwara, B., Abuhelwa, A. Y., Kichenadasse, G., … & Hopkins, A. M. (2021). The obesity paradox in early and advanced HER2 positive breast cancer: pooled analysis of clinical trial data. NPJ breast cancer, 7(1), 1-6.
 Rajbhandari‐Thapa, J., Metzger, I., Ingels, J., Thapa, K., & Chiang, K. (2022). School climate‐related determinants of physical activity among high school girls and boys. Journal of Adolescence.
 Mehta, R. S., Song, M., Nishihara, R., Drew, D. A., Wu, K., Qian, Z. R., … & Chan, A. T. (2017). Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes. Gastroenterology, 152(8), 1944-1953.
 Axelrad, J. E., Lichtiger, S., & Yajnik, V. (2016). Inflammatory bowel disease and cancer: the role of inflammation, immunosuppression, and cancer treatment. World journal of gastroenterology, 22(20), 4794.
 Leger, D., Beck, F., Richard, J. B., & Godeau, E. (2012). Total sleep time severely drops during adolescence.