Risk factors such as smoking behind almost half of cancer deaths, finds study

Smoking, drinking alcohol, being overweight and other risk factors are responsible for almost half of all cancer deaths worldwide, according to the largest study of its kind.

Cancer is the second leading cause of death globally, and exposure to risk factors plays a key role in the biology and burden of many cancer types. Doctors do not know the exact causes of cancer, and not every case or death is avoidable, but there are risk factors that can increase people’s chance of developing it.

Now researchers at the University of Washington’s school of medicine have become the first to work out how risk factors contribute to cancer deaths globally.

Smoking, alcohol use, and a high body mass index (BMI) are the biggest contributors. In total, risk factors are responsible for nearly 4.45m cancer deaths a year, according to the findings published in the Lancet that used the Global Burden of Diseases, Injuries, and Risk Factors (GBD) 2019 study.

That represents 44.4% of all cancer deaths worldwide. Half of all male cancer deaths in 2019 (50.6%, or 2.88m) were due to estimated risk factors, compared with more than a third of all female cancer deaths (36.3%, or 1.58m). “This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world,” said Dr Christopher Murray, the director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington’s school of medicine and a co-senior author of the study.

“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 regionally, nationally, and globally.”

The leading risk factors globally for cancer deaths for both sexes were smoking, followed by alcohol use and high BMI.

The biggest cause of risk-attributable cancer deaths for both women and men globally was tracheal, bronchus and lung cancer. These account for 36.9% of all cancer deaths attributable to risk factors.

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

The five regions with the highest cancer death rates owing to risk factors were central Europe (82 deaths per 100,000 population), east Asia (69.8 per 100,000), high-income North America (66 per 100,000), southern Latin America (64.2 per 100,000) and western Europe (63.8 per 100,000).

While not all cases or deaths are preventable, Cancer Research UK, the world’s largest independent cancer research organisation, says stopping smoking, cutting back on alcohol, maintaining a healthy weight, enjoying the sun safely and eating a balanced diet can all improve the odds in your favour.

Writing in a linked comment, Prof Diana Sarfati and Dr Jason Gurney of the University of Otago, New Zealand, who were not involved in the study, said preventing cancer by eradicating or reducing exposure to risk factors was “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,” they said.