Factors such as obesity and alcohol consumption are contributing to a worrying rise in global cancer cases among younger people, a study suggests.
Researchers estimated there had been a 79% hike in new cases of cancer in those aged under 50 between 1990 and 2019.
However, rates in the UK were stabilised from 2010 to 2019 with the annual mortality rate from early-onset cancer “steadily decreasing”.
A team from the University of Edinburgh and the Zhejiang University School of Medicine in China analysed data from the Global Burden of Disease 2019 Study for 29 cancers in 204 countries and regions.
They looked at new cases, deaths, health consequences and risk factors in people aged 14 to 49, estimating an annual percentage for each year.
In 2019, there were 3.26 million new cancer diagnoses for under-50s, an increase of 79.1% since 1990.
Deaths were also up by 27.7%.
Researchers said that while genetics are likely to play a part, smoking, alcohol consumption and diets high in meat and salt but low in fruit and milk are the “main risk factors”, along with factors such as excess weight, low physical activity and high blood sugar.
Breast cancer made up the largest proportion of cases – 13.7 per every 100,000 people – while windpipe and prostate cancer cases are growing the fastest at 2.28% and 2.23% per year respectively.
However, early-onset liver cancer cases were down by 2.88% each year.
Study author Dr Xue Li, of the Centre for Global Health at the University of Edinburgh’s Usher Institute, said while early-onset cancer in the UK showed an “upward trend” from 1990 to 2010, “the overall incidence rate remained stable” from 2010 to 2019.
She added: “Fortunately, the annual mortality rate from early-onset cancer in the UK has been steadily decreasing, a testament to the outstanding cancer screening and treatment efforts over the past three decades.”
Publication of the study – in the journal BMJ Oncology – comes after the charity Cancer Research UK claimed advances in cancer care have helped save 1.2 million lives in the UK since the mid-1980s.
The figure includes an estimated 560,000 fewer lung cancer deaths, 236,000 deaths from stomach cancer, 224,000 bowel cancer deaths and 17,000 breast cancer deaths.
The charity said the improvement is down to progress in cancer prevention, as well as diagnosis and treatment, including improvements in radiotherapy, the use of cancer screening programmes, drug development and gene discoveries.
Dr Claire Knight, senior health information manager at Cancer Research UK, said: “It’s not fully clear what is driving the rise in early-onset cancers, but exposure to risk factors in earlier life, better detection of cancer and genetics might all play a part.”
Dr Knight said cancer remains “primarily a disease of older age”, however “alarming” the findings of the study might seem.
“We need more research to examine the causes of early-onset cancer for specific cancer types, like our BCAN-RAY study that is looking at new ways to identify younger women at higher risk of breast cancer,” she added.
“If people are concerned about their cancer risk, there are lots of ways to help reduce this, such as not smoking, maintaining a balanced diet, getting plenty of exercise and staying safe in the sun.”
Montserrat Garcia-Closas, a professor of epidemiology at the Institute of Cancer Research, said the study “seeks to address important questions on global surge in early-onset cancers” but there are “limitations with the methodology make it unclear what these findings add to current literature”.