Young people get sick more often than they used to: And no one knows why

For many years, cancer was considered to be a disease primarily associated with old age, with the greatest number of diagnoses coming after the age of 50. In recent years, however, the situation has begun to change. According to the latest statistics, cancer is becoming more common in younger adults. This is a fact that doctors and scientists are encountering all over the world, despite the fact that overall cancer mortality rates are falling in Western countries. What is happening and what are the causes?

While the overall picture is encouraging, with more patients surviving than ever before thanks to advances in treatment and early detection, the increasing number of diagnoses in young people is hindering this positive trend. Most striking is the increase in colorectal cancer in men and breast cancer in women.

The shift in the age of diagnosis

Reports from the American Cancer Society show that the number of new cases is increasing in people under 50, while stagnating or declining in older generations. A significant shift is seen in the aforementioned colorectal cancer, which has become the leading cause of cancer deaths in younger and middle-aged men and the second leading cause of cancer deaths in women over the past two decades. The proportion of diagnoses in this age group has almost doubled since the mid-1990s.

However, this is not a situation limited to the United States – New Zealand, Swedish and Scottish statistics show similar increases. According to a study in the journal BMJ Oncology, between 1990 and 2019, early-onset cancers increased by 79% globally, and deaths by 28%. Cancers of the digestive system – colon, rectum, stomach and pancreas – have seen a particularly significant increase.

While cancer remains a disease primarily of the elderly – more than 85% of cases are in people over 50 – younger adults are the only group in which its incidence is rising.

Searching for causes: lifestyle, environment and microbiome

Why young people fall ill before their parents or grandparents remains a mystery. The culprit is unlikely to be a single factor, but a combination of factors.

The Western diet – high in ultra-processed foods, red meat, sugar and sugary drinks – is often cited as promoting obesity and chronic inflammation. It is obesity that has long been ranked as a major risk factor, but it does not in itself explain the increase. In fact, some patients treated for colorectal cancer are thin, play sports and have no genetic burden.

Therefore,other influences have also been suggested, such as increased use of antibiotics or exposure to microplastics or chemicals that accumulate in the body from a range of products. Research also shows possible links to maternal obesity during pregnancy or to early developmental factors such as breastfeeding or mode of delivery. However, these are still mere speculations and await confirmation.

Given the sharp increase in colorectal cancer, the main hypotheses include a transformation of the gut microbiome. Changes in diet and lifestyle since the 1990s could lead to the dominance of certain types of harmful bacteria in the gut.

What does this mean for us?

Although scientists do not yet have clear answers, it is essential that society adapts. Although early-onset cancers are relatively rare, there is a need to raise awareness of screening tests that help detect the disease early – for example, some cancer societies have lowered the recommended age for first colorectal cancer screening from 50 to 45.

Although the increase in diagnoses in younger age groups is a cause for concern, research also offers hope. Thanks to advances in treatment and earlier detection, cancer deaths have fallen by more than a third since the early 1990s. Fewer people are smoking, modern therapies are more effective and survival is being extended. Cancer therefore remains a serious threat, but it is also a disease against which we have increasingly powerful tools.

Science does not yet have an answer to why younger and younger people are facing it. Finding the cause will therefore be crucial not only for the current generation of people in their thirties and forties, but also for those who come after them.