Babies born with a higher-than-average birth weight may face a greater risk of developing bowel cancer at a younger age, according to new research.
Diagnoses of bowel cancer among people under 50 have been increasing in the UK, a trend that has concerned doctors and researchers because the reasons behind the rise are still not fully understood.
A study published by the Yale School of Public Health has now identified two factors linked to a higher likelihood of early-onset bowel cancer: excess weight at birth and having an older father.
The findings are particularly notable as research suggests the UK is seeing a growing number of larger newborns, sometimes referred to as “giant babies.”
The medical term for the condition is foetal macrosomia, derived from the Greek for “big body.” It describes babies born weighing 8lb 13oz or more and is now thought to affect around one in ten newborns in the UK.
Experts say macrosomia is often associated with parental obesity or diabetes, raising questions about how parents’ health and lifestyle before and during pregnancy may influence a child’s long-term disease risk.
The study adds to growing concern around early-onset bowel cancer, an issue brought into sharp public focus by Dame Deborah James, the journalist and campaigner known as Bowel Babe, who died from the disease in 2022 at the age of 40.
Since her death, the Bowel Babe Fund, established in Dame Deborah’s honour to support cancer research projects, has raised more than £20 million.
Dame Deborah James, nicknamed the ‘bowel babe’ raised more than £20mn for Cancer Research and is credited for increasing awareness of the disease, which killed her in 2022 aged 40
Every year, around 44,000 people are diagnosed with bowel cancer in the UK. The disease, also known as colorectal cancer, kills around 17,000 over the same time period.
Obesity, lack of exercise and alcohol have all been shown, over time, to raise the risk of the disease.
And, until recently, all research suggested the chances of developing bowel cancer rises with age.
For this reason, the NHS screens those between 50 and 74 for bowel cancer. This involves a biannual at-home poo test, called a faecal immunochemical test (FIT).
However, studies show that, in recent decades, younger patients are increasingly developing the deadly disease.
In Britain, those under 49 today are around 50 per cent more likely to develop bowel cancer than people of the same age in the early 1990s.
For the new study – published in the journal Cancer – researchers matched 1,221 patients who had been diagnosed with bowel cancer before the age of 39 with 61,000 cancer-free controls.
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Results showed that men were around a third more likely to develop the disease before the age of 50 than women, consistent with existing trends.
They argue this may be because higher levels of free testosterone – a male sex hormone which drops with age – have been linked to an increased risk of the disease.
But, significantly, the study also found convincing evidence that birth weight has a significant impact on bowel cancer risk.
In females, every half a kilo difference in birth weight was associated with a 10 per cent increased risk. No such association was observed in males.
A similar pattern was observed for paternal age – the age of a man at the time of conception.
The researchers say it’s still unclear why this is the case, but theorise that it could be linked to whether expectant mothers are overweight or have diabetes.
Previous studies have suggested that these conditions can disrupt the production of growth hormones needed during pregnancy, potentially impacting the health of children later in life.
In turn, mothers who are overweight or have diabetes are more likely to have so-called giant babies, according to leading researcher Dr Dimitrios Siassakos, professor of obstetrics at University College London.
Dr Siassakos claims that around one in ten babies in the UK now fall into this category.
Experts say this might explain why larger than average babies are more likely to develop early age bowel cancer – and why the disease is on the rise in this age group.
The Yale study also found that young women whose fathers were 35 or older at the time of conception had a significantly higher risk of early onset bowel cancer.
Older paternal age has been linked to a number of birth defects, including a cleft lip or hole in the diaphragm, with the risk increasing with each year of paternal age.
Some cancers also become more common. Previous studies have found that for every five years older the father is, the risk of a certain type of childhood leukemia increased by 13 per cent.
Separate research has highlighted the increased risk of brain and breast cancers.
Now, experts think there may be a link with early age bowel cancer.
The researchers suggested this may be due to the increase in rate of de novo mutations – genetic changes that arise spontaneously rather than being inherited – among children born to older fathers.
While several theories were highlighted by the study, the researchers acknowledged further studies are needed for validation and that there is unlikely to be one cause behind the ‘mysterious’ rise in early onset cancers.
