Bowel (colorectal) cancer is on the increase among young adults in Europe, a new study indicates.

Around 2,500 people are newly diagnosed with the disease every year in Ireland and over the last decade, the number of new cases has risen in most European countries. However until now, it has been unclear about the rates among younger adults.

Researchers in the Netherlands decided to look into this further. They used data from over 143 million people aged between 20 and 49 from 20 countries, including Ireland, the UK, Germany, Finland, Slovenia and the Czech Republic.

Between 1990 and 2016, almost 188,000 cases of bowel cancer were diagnosed in the 20 countries.

The researchers found that the rate of the disease increased the most among the youngest age group (20-29 years). Between 2004 and 2016, the rate of cases in this age group increased by almost 8% per year.

Among those aged 30-39, the incidence increased also, but less steeply - by an average of almost 5% per year between 2005 and 2016.

Among those aged 40-49, bowel cancer rates fell slightly between 1990 and 2004, but then increased by 1.6% per year between 2004 and 2016.

The researchers noted that new cases of bowel cancer rose significantly among people aged 20-39 in 12 countries, including Ireland, the UK, Belgium, Germany, the Netherlands, Norway and Sweden.

However, they also noted that the number of deaths from bowel cancer did not significantly change between 1990 and 2016 among those aged 20-29, while among those aged 30-39, death rates fell by 1.1% per year. Those aged 40-49 saw the rate of deaths fall by 2.4% in the same period.

The researchers pointed out that the study was observational, so it cannot establish cause. However, they suggested that a number of factors may be behind the trend, such as the rise in obesity, a lack of physical activity, smoking and alcohol intake.

"Bowel cancer in young adults is in part due to hereditary cancer syndromes, but most cases are sporadic...Until the underlying cause of this trend is identified, it would be a good idea to raise clinicians' awareness and identify factors possibly associated with this trend," the Dutch team said.

Details of these findings are published in the journal, Gut.