Lifestyle and the ‘lag effect’: What’s causing the rise of early onset cancer

Brendan Moynihan describes himself as very fit and healthy.

“I played competitive sports all my life, and typically, I run four mornings a week,” says the 40-year-old Irishman who works in marketing.

Doctors dismissed Brendan Moynihan as too young to have a “serious” health issue.Credit: Simon Schluter

So it was unusual when, in August 2022, Moynihan found himself unable to run more than one kilometre without needing to stop – he felt “zapped”. A visit to his GP in Melbourne proved unhelpful.

“I was dismissed as being just too young for anything serious,” he recalls. “He said I was probably just run down.”

Moynihan took the doctor’s word for it and put his tiredness down to poor sleep.

But two months later, he felt even more exhausted, and there was now blood in his stools. Moynihan returned to his GP and, this time, was told he likely had haemorrhoids. No further investigation was ordered.

If it weren’t for the fact that running was his stress relief – and he was now too tired to run at all – he might have accepted the doctor’s words once again. But he couldn’t bear the thought of losing his outlet. So he scheduled an appointment with a new doctor, who immediately ordered blood tests, then a colonoscopy.

At 5.30pm on Christmas Eve, 2022, Moynihan met with the surgeon and was told he had stage 2 bowel cancer. Within two weeks he had surgery to remove about half of his colon.

In reflective moments before the surgery, Moynihan, then 38, wondered what he had done wrong.

“I did almost blame myself. I was like, ‘OK, was my diet bad?’ It wasn’t. ‘Was I stressed at work?’ I wasn’t. ‘Did I not get enough sleep?’ I was getting plenty of sleep. But unfortunately, I could not help but go, ‘Well, there’s a reason this has happened to me, and it is probably because of my own choices’.”

Age remains a significant risk factor for cancer – the average age of diagnosis is 66 – so why are young people, like Moynihan, increasingly being diagnosed?

Dawson’s Creek star James Van Der Beek, 47, recently revealed he had been diagnosed with stage 3 colon cancer. He is the latest in a long line of young celebrities with cancer, including Ben Stiller, diagnosed with prostate cancer at 48; Kylie Minogue, who was 36 when she was diagnosed with breast cancer; Chadwick Boseman, who died in 2020 at 43 from colon cancer; and Princess Catherine, who was 42 when she was diagnosed earlier this year.

Between 1990 and 2019, the incidence of early onset cancer – diagnosed in people aged 18 to 49 – increased by 79.1 per cent worldwide. High-middle and middle socio-demographic index regions were the worst affected.

Models predict that those numbers will increase another 30 per cent between 2019 and 2030.

A paper published in Nature earlier this year, examining the possible causes, pointed out that many of these early-onset cancers affect the digestive system. The suggestion was that they coincide with the rise of obesity and a diet largely comprised of ultra-processed foods (UPFs).

Yet rising rates among fit and healthy adults, like Moynihan, suggest this is not the whole story.

Lifestyle and the lag effect

Up to 10 per cent of cancers are caused by hereditary genetic changes, but what about the rest?

“Lifestyle has a lot to do with it,” says Flinders University Associate Professor George Barreto, a gastrointestinal, HPB and liver transplant surgeon, academic and researcher. “Not just of the individual, but their parents as well.”

Australians drink less alcohol than we did in the 1970s and 80s, when consumption levels peaked, and less than 10 per cent of us smoke daily (compared with 36 per cent in 1977), but Barreto says there’s a “lag effect”.

“Patients today who are in their 30s and 40s – their parents would have been at the peak of the drinking and smoking eras, and possibly even did that during pregnancy.”

In an editorial co-authored by Barreto in August, he argued that stressors at two critical periods in an individual’s life – namely, the perinatal and adolescent years – resulted in epigenetic modifications that may partially explain the rise of early-onset cancer.

It built upon a 2021 paper, published in Frontiers Oncology, which hypothesised that exposure of the fetus to stressors, including maternal malnutrition, smoking or alcohol, led to epigenetic changes to help the fetus cope.

“Exposure to the same stressors, early in the life of that individual, facilitates a re-activation of these ‘responses designed to be protective’ but ultimately resulting in a loss of regulation at a metabolic and/or genetic level,” wrote Barreto.

However, he says there’s a lot more to the conversation than alcohol and cigarettes.

Over the last 30 to 50 years antibiotic use has increased; our diets have shifted from mainly unrefined foods to one where ultra-processed foods comprise 42 per cent of the Australian diet; obesity rates tripled among women and quadrupled among men between 1975 and 2022; children are 50 per cent less active than they were 100 years ago; adults are increasingly sedentary; screen time is replacing time outdoors; and sleep quality may be declining while complaints of sleep disorders are increasing.

As for the rise of cancer among those with a good diet who exercise, sleep well and don’t smoke or drink too much, Barreto reminds us that we all have different immune, hormonal and nutritional profiles and respond differently.

“The human being is not a mathematical model,” he says. “Individuals’ responses to stressors are different, but we know what the stressors are.”

Unknowns in the environment

Adrian Esterman, a professor of biostatistics at the University of South Australia, agrees the most likely explanation for early-onset cancer is lifestyle choices, but he adds it could also be an environmental issue.

Pesticide use in Australia has more than tripled since 1990; carcinogenic “forever chemicals” have been found in the tap water of many Australian households, and in some areas are at 50 times the levels deemed safe; potentially harmful microplastics exist everywhere; while air pollution has also been linked with cancer.

Forever chemicals have been found in Australians’ tap water, but the risks remain unclear.Credit: Sam Mooy

Yet, the impacts of environmental factors remain unclear. “If it was going to affect us, then we’d see increasing cancer rates overall, which we’re not doing,” says Esterman. “So why would it only hit younger people?”

There is complexity to the issue, says Dr Nicholas Chartres, senior research fellow at the University of Sydney’s medicine faculty. However, he returns to Barreto’s point about critical exposure windows, such as in utero and childhood.

“Being exposed to all these contaminants in the critical developmental window makes us more susceptible and likely to develop a non-communicable disease at an earlier life stage,” says Chartres.

“This includes the 350,000-plus chemicals now registered for use; fossil-fuel consumption and petrochemical production that is more than 15 times higher than they were in the 1950s; a food system that is filled with UPFs made from chemicals and wrapped in plastic with chemicals; and an agricultural system that has become dependent on pesticides.”

Megan Varlow, director of cancer control policy at Cancer Council Australia, says they are “not aware of strong evidence” to suggest environmental factors may increase cancer risk.

She cites a 2014 Oxford University Million Women study where 600,000 women aged 50 or over were asked whether they ate organic food and monitored their health for nine years.

“They looked at cancers specifically linked to pesticides, such as breast cancer and soft tissue cancer, and found no evidence that a woman’s overall cancer risk was decreased if she generally ate organic food,” Varlow says. “Foods Standards Australia New Zealand has also advised that the chemical residues on conventionally produced foods are so low that they aren’t considered a health risk.”

What age should you get cancer screening?

• Breast screening is recommended for women aged 50-74 and should be repeated every two years. Women aged 40-49 and over 74 are also eligible.
• Bowel cancer screening home test kits are sent to people aged 50-74 by the Australian government every two years, and now people aged 45-49 can also request a free screening kit.
• Women aged 25-74 are invited to screen every five years at their local healthcare provider under the new Cervical Screening Program.

Is there any good news?

“We have much, much better treatments, and we’re right on the brink of a huge revolution in treatments, and that is immunotherapy,” says Estermen. “I’m not sure that we’ll see cancer instances going down, but we’ll see huge improvements in survival.”

We already are, adds Varlow: “Mortality rates have been decreasing for people in their 30s and 40s.”

And by improving our lifestyle choices, we both reduce our risk of getting cancer and, if we do get it, improve our likelihood of a good outcome.

“We encourage Australians to reduce their risk of cancer by eating a healthy, balanced diet, limiting alcohol, being physically active at least 30 minutes a day, staying sun safe and quitting smoking,” says Varlow.

To that list, Esterman adds limiting screen time and focusing on getting better sleep. We should also utilise cancer screening and vaccines for HPV (the common infection is the cause for most cases of cervical cancer).

Moynihan, now a Bowel Cancer Australia advocate who took a year off work to recover physically and mentally, says his energy is slowly returning, but he is still awaiting follow-up scans.

“I heard this beautiful saying in my own journey: if you listen to your body when it whispers, you don’t have to hear it when it screams. And for me, it was eye-opening in that, for years, and maybe it’s more of a male thing, I would be unwell, but I’ll persevere,” he says.

“We all know our own bodies, and if something is amiss or doesn’t feel right, just ask the question.”

What symptoms should you watch for?

The Cancer Council advises people to keep an eye out for any unusual changes to their bodies, such as:

• Lumpiness or a thickened area in your breasts, any changes in the shape or colour of your breasts, unusual nipple discharge, a nipple that turns inwards (if it hasn’t always been that way) or any unusual pain.
• A lump in the neck, armpit or anywhere else in the body.
• Sores or ulcers that don’t heal.
• Coughs or hoarseness that won’t go away, or coughing up blood.
• Changes in toilet habits that last more than two weeks, blood in a bowel motion.
• New moles or skin spots, or ones that have changed shape, size or colour, or that bleed.
• Unusual vaginal discharge or bleeding.
• Unexplained weight loss.

For cancer information and support call Cancer Council’s 13 11 20 Information and Support line

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