LONDON - Over the past three decades, rates of cancer in G20 nations have risen faster among people aged 25 to 29 than in any other age group, reports the Financial Times.

Its analysis of data from the University of Washington School of Medicine reveals that rates for 25- to 29-year-olds rose 22% between 1990 and 2019; by contrast, cases in over-75s have declined since their peak in 2005.

It’s unclear why younger people should be more vulnerable to cancer now than in previous generations, but a clue may lie in the types of cancer afflicting the young.

For instance, among 15- to 39-year-olds, cases of colorectal cancer are 70% higher since 1990, the FT found. Separate research has suggested that, in the US this year, 13% of colorectal cancer cases will be in people under 50, along with 7% of deaths.

All this points to the shift to modern diets in the 1960s, with more processed foods, and higher levels of sugar and saturated fats, being a likely factor, says oncologist Dr Frank Sinicrope, of the Mayo Clinic in the US.

Increasingly, the focus on scientific inquiry in this field is on changes to the microbiome (the microbes that live within us, mainly in the gut) as well as obesity.

Other factors might include the move to more sedentary lifestyles and the impact on circadian rhythms of repeated exposure to bright light at night.