Smoking, alcohol use, high BMI and other known risk factors were responsible for nearly 4.45 million global cancer deaths in 2019, according to a research published in The Lancet using the Global Burden of Diseases, Injuries, and Risk Factors (GBD) 2019 study.
The new study is the first to estimate how a comprehensive list of risk factors contribute to cancer deaths and ill health globally, regionally and nationally, across age groups, for both sexes, and over time. Despite being the second leading cause of death worldwide after cardiovascular disease, till date, most studies of cancer burden have analysed single risk factors globally or multiple risk factors in select countries.
“This study illustrates that the burden of cancer remains an important public health challenge that is growing in magnitude around the world. Smoking continues to be the leading risk factor for cancer globally, with other substantial contributors to cancer burden varying,” Dr Christopher Murray, 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 said in the report.
Using results from the GBD 2019 study, the authors investigated how 34 behavioral, 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. The 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% 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% of all DALYs in that year.
Behavioral 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. Almost 2.88 million deaths in men (50.6% of all male cancer deaths) could be attributed to the risk factors studied, compared to 1.58 million deaths in women (36.3% 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 leading cause of risk-attributable cancer death for both men and women globally was tracheal, bronchus and lung cancer, which accounted for 36.9% of all cancer deaths attributable to risk factors, the study said. This was followed by colon and rectum cancer (13.3%), oesophageal cancer (9.7%), and stomach cancer (6.6%) in men and cervical cancer (17.9%), colon and rectum cancer (15.8%) and breast cancer (11%) in women.
Researchers found differences in men and women across two major categories: behavioral risks and environmental and occupational risks. With behavioral risks, males (33.2%) had almost four times the cancer DALYs attributable to smoking than females (8.9%). For alcohol use, males (7.4%) had more than three times the cancer DALYs than females (2.3%). The higher cancer DALYs in males may be driven by men being more likely to smoke and drink than women.
The five regions with the greatest cancer death rates due to risk factors were central Europe (82 deaths per 1,00,000 population), East Asia (69.8 per 1,00,000 population), high-income North America (66 per 1,00,000 population), Southern Latin America (64.2 per 1,00,000 population) and Western Europe (63.8 per 1,00,000 population).
Between 2010 and 2019, cancer deaths due to risk factors rose by 20.4% globally, increasing from 3.7 million to 4.45 million. Ill health due to cancer increased by 16.8% over the same period, rising from 89.9 million to 105 million DALYs. Metabolic risks accounted for the greatest percentage increase in cancer deaths and ill health, with deaths increasing by 34.7% (6,43,000 deaths in 2010 to 8,65,000 in 2019) and DALYs by 33.3% (14.6 million in 2010 to 19.4 million in 2019).
The authors acknowledge some limitations to their study that are mostly inherent in the data sources and knowledge available. “Due to a lack of data, there is greater uncertainty regarding estimates for lower income countries compared with higher ones. Expanding data availability on risk factors and cancer burden is crucial to providing location-specific information and improving estimates,” the authors said.