WASHINGTON: Smoking, alcohol use, high body mass index (BMI), and other known risk factors were responsible for nearly 4.45 million global cancer deaths in 2019, according to study published in The Lancet journal on Friday.
The 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.
"This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world," said Christopher Murray, Director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, US.
"Smoking continues to be the leading risk factor for cancer globally, with other substantial contributors to cancer burden varying," said Murray, a co-senior author of the study.
Using results from the Global Burden of Diseases, Injuries, and Risk Factors (GBD) 2019 study, the researchers investigated how 34 behavioural, metabolic, and environmental and occupational risk factors contributed to deaths and ill health due to 23 cancer types in 2019.
Changes in cancer burden between 2010 and 2019 due to risk factors were also assessed.
Estimates of cancer burden were based on mortality and disability-adjusted life-years (DALYs), a measure of years of life lost to death and years lived with disability.
In addition to 4.45 million cancer deaths which made up 44.4 per cent of all cancer deaths in 2019, risk factors included in the analysis accounted for 105 million cancer DALYs globally for both sexes in 2019 -- 42.0 per cent of all DALYs in that year, the researchers said.
Behavioural risk factors such as tobacco use, alcohol use, unsafe sex, and dietary risks were responsible for the vast majority of cancer burden globally, accounting for 3.7 million deaths and 87.8 million DALYs in 2019, they said.
The study shows that almost 2.88 million deaths in men (50.6 per cent of all male cancer deaths) could be attributed to the risk factors studied, compared to 1.58 million deaths in women (36.3 per cent of all female cancer deaths).
The leading risk factors globally for cancer deaths and ill health for both sexes were smoking, followed by alcohol use and high BMI, the researchers said.
The leading cause of risk-attributable cancer death for both 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, they said.
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 (15.8per cent), and breast cancer (11 per cent) in women.
Ill health attributed to environmental and occupational, behavioural, and metabolic risk factors increased with age, peaking in the 70s depending on countries' socio-demographic Index (SDI), with countries on the higher end of the spectrum tending to peak at later ages.
The five regions with the greatest cancer death rates due to risk factors were central Europe (82 deaths per 100,000 population), East Asia (69.8 per 100,000), high-income North America (66.0 per 100,000), Southern Latin America (64.2 per 100,000), and Western Europe (63.8 per 100,000).
Patterns of cancer deaths and ill health due to environmental and occupational, behavioural, and metabolic risks differed around the world, with unsafe sex a leading risk factor for ill health in locations at the lower end of the SDI spectrum.
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, according to the researchers.
Ill health due to cancer increased by 16.8 per cent over the same period, rising from 89.9 million to 105 million DALYs, they said.
Metabolic risks accounted for the greatest percentage increase in cancer deaths and ill health, with deaths increasing by 34.7 per cent and DALYs by 33.3 per cent.
"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," said Lisa Force, Assistant Professor at IHME.