Smoking, drinking alcohol, being overweight and other known risk factors were responsible for nearly 4.45 million cancer deaths around the world in 2019, new research suggests.

The study is the first to estimate how a list of 34 risk factors contribute to cancer deaths and ill health globally, regionally and nationally, across age groups, genders and over time.

According to the research, 4.45 million represents 44.4 per cent of all cancer deaths across the world in 2019.

"This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world," Dr Christopher Murray, director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington's School of Medicine, said.

"Smoking continues to be the leading risk factor for cancer globally, with other substantial contributors to cancer burden varying.

"Our findings can help policymakers and researchers identify key risk factors that could be targeted in efforts to reduce deaths and ill health from cancer."

Behavioural risk factors such as smoking, alcohol use, unsafe sex and dietary risks were responsible for the vast majority of the global cancer burden, accounting for 3.7 million deaths, the study found.

Using the Global Burden of Diseases, Injuries and Risk Factors (GBD) 2019 study, researchers investigated how 34 behavioural, metabolic, environmental and occupational risk factors contributed to deaths and ill health due to 23 cancer types in 2019.

Estimates of cancer burden were based on deaths and disability-adjusted life-years (DALYs) - a measure of years of life lost to death and years lived with disability.

According to the study, risk factors included in the analysis accounted for 105 million cancer DALYs globally in 2019 - 42 per cent of all DALYs in that year.

Researchers found the leading cause of risk-attributable cancer death for men and women globally was tracheal, bronchus and lung cancer, which accounted for 36.9 per cent of all cancer deaths attributable to risk factors.

This was followed by colon and rectum cancer (13.3 per cent), oesophageal cancer (9.7 per cent) and stomach cancer (6.6 per cent) in men; and cervical cancer (17.9 per cent), colon and rectum cancer (15.8 per cent) and breast cancer (11 per cent) in women.

Between 2010 and 2019, cancer deaths due to risk factors rose by 20.4 per cent globally, increasing from 3.7 million to 4.45 million.

"Policy efforts to reduce exposure to cancer risk factors at the population level are important and should be part of comprehensive cancer control strategies that also support early diagnosis and effective treatment," Dr Lisa Force, assistant professor in Health Metrics Sciences at IHME at the University of Washington's School of Medicine, said.

Writing in a linked comment, professor Diana Sarfati and Dr Jason Gurney of New Zealand's University of Otago, who were not involved in the study, said: "The primary prevention of cancer through eradication or mitigation of modifiable risk factors is our best hope of reducing the future burden of cancer.

"Reducing this burden will improve health and wellbeing and alleviate the compounding effects on humans and the fiscal resourcing pressure within cancer services and the wider health sector."

The study is published in The Lancet.