Why is cancer becoming more common among millennials?

It’s long been known that processed foods and a sedentary lifestyle are not good for us, but a new study has confirmed a possible link between them and an alarming increase in early-onset cancer among millennials.

Over the past 30 years, cancer rates in the G20 nations have increased faster for 25- to 29-year-olds than any other age group – by 22% between 1990 and 2019, according to the Financial Times (FT). The UK newspaper analyzed data from the Institute for Health Metrics and Evaluation at the University of Washington School of Medicine and found that cancer diagnoses for 20- to 34-year-olds in these Western countries are now at their highest level in three decades. Meanwhile, cancer cases in those over 75 have declined since 2005.

Apart from the sometimes tragic health consequences of these early-onset diagnoses, there are also long-term policy implications: the estimated global cost of cancer from 2020 to 2050 is $25.2tn at constant 2017 prices. This is “equivalent to an annual tax of 0.55% on global gross domestic product,’’ the researchers said.

So what is causing this surge in numbers? While earlier detection plays a part, the FT analysis and a number of other recent studies say changes in nutrition including eating more processed food, a more sedentary lifestyle and exposure to more environmental risk factors such as toxins are likely to play a big part.

The Western lifestyle changed dramatically in the 1950s and ’60s and children born from then on will have been exposed to these changes from a very young age, something scientists call the “birth cohort effect” – where each successive generation has a higher risk of developing cancer later in life.

“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,’’ said Shuji Ogino, a professor at Harvard Chan School and Harvard Medical School and the co-author of a groundbreaking study into early-onset cancers.

Ogino and colleagues analyzed global data on 14 cancer types that were becoming more common in younger adults. Possible risk factors for early-onset cancer were identified as a highly processed food, an increase in sugary drinks and alcohol.

In the US, over 60% of calories eaten are now ultra-processed, while in the UK it’s 57%, the highest in Europe, according to Prof Tim Spector and Dr Chris van Tulleken, experts on the impact of ultra processed foods on the microbiome. Our microbiome produces vitamins, regulates our immune system and helps digest food.

An unhealthy microbiome altered by diet, lifestyle and antibiotic use can be ”another notable contributor to tumour development”, according to the Ogino study. It has found that among the 14 early-onset cancers, eight relate to the digestive system, “indicating the pathogenic importance of both the oral and intestinal microbiome”.

As developing countries catch up in wealth, they also tend to emulate Western-style diets and lifestyles – which is leading to rising cancer rates among people under 50, according to the FT analysis. It found that between 1990 and 2019, cancer rates for 15- to 39-year-olds increased significantly faster in upper-middle-income countries, such as Brazil, Russia, China and South Africa, compared to high-income countries: by 53% compared to 19%.

Without interventions and preventive measures, the prognosis is not good for future generations. Already the current cohort of young adults has a higher risk of early-onset cancer than the middle age and older generation.

As well as calling for more research and raising awareness of the benefits of a healthy lifestyle and diet, Ogino’s study says policy interventions such as “regulation of industries that produce tobacco, ultra processed foods and beverages could potentially have an effect on cancer risk”.

Meanwhile, some clinicians are calling for a reduction in eligibility age for cancer screening programmes, reports the FT.

With non-communicable diseases, including cancer, now accounting for 41 million global deaths every year, “it is important to ensure stakeholders, industries, countries, and sectors strive to achieve common health and healthcare goals and work collaboratively to do so,” the World Economic Forum points out in its report, Global Health and Healthcare Strategic Outlook: Shaping the Future of Health and Healthcare.