Cancer is more commonly associated with older age. However, growing global evidence from the past three decades has pointed to an increasing number of cases among young adults.

While genetics are likely to play a part in the rise of cancer cases in young people, experts say that smoking, alcohol consumption and diets high in meat and salt but low in fruit and milk are the main risk factors.

The University of Edinburgh-led team looked at the impact of 29 cancers on people aged between 14 and 49 years-old in more than 200 countries and regions.

Their analysis found that cancer cases worldwide rose from 1.82 million in 1990 to 3.26 million in 2019.

Breast cancer accounted for the largest number of cases – 13.7 per every 100,000 people.

The fastest rise was seen in windpipe and prostate cancers, growing 2.38 per cent and 2.23 per cent per year respectively.

The highest rates of early onset cancers in 2019 were seen in North America, Australasia, and Western Europe.

Based on the trends for the past three decades, researchers estimate that the global number of new early onset cancer cases and associated deaths will rise by a further 31 per cent and 21 per cent, respectively, in 2030, with those in their 40s the most at risk.

Further research is needed to fully understand the reasons driving the concerning growth in cases.

It is unclear how screening and early life exposure to environmental factors may be influencing the observed increase, researchers say.

To conduct their analysis, the study team examined data from the Global Burden of Disease 2019 Study.

They looked at figures related to new cases, deaths, health consequences – known as disability-adjusted life years or DALYs – and risk factors for all those aged 14 to 49 to estimate the annual percentage change between 1990 and 2019.

The research team highlight that variable quality of cancer registry data in different countries may have led to under-reporting and under-diagnosis.

The study was led by scientists from the University of Edinburgh and the Zhejiang University School of Medicine in China.

Dr Xue Li, Study author, from the Centre for Global Health at the University of Edinburgh’s Usher Institute said: ” Research on the drivers of early-onset cancer is currently quite limited. The hypotheses we have presented are based on existing data and literature. The impact of air pollution, climate change, or birth cohort effect on the increasing trend of young cancer is not fully investigated.

” We strongly encourage more researchers and funding support to be dedicated to the field of early-onset cancer. This will help elucidate the factors behind this phenomenon and ultimately reduce the social, economic, and familial burden posed by early-onset cancer.”

The study can be viewed at BMJ Oncology