A study published in The Lancet, ‘The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019’, has found metabolic risk factors were identified as leading contributors to cancer deaths and disability-adjusted life years between 2010 and 2019. This was followed by behavioural, environmental and occupational risk factors.
Cancer is the second leading cause of death worldwide and although many cancers are genetically triggered and cannot be prevented, some cancers are caused by aberrant exposure to known risk factors, which are otherwise known as risk-attributable cancers. Restricting exposure to these modifiable risk factors can lead to a reduction in cancer-related deaths and disability-adjusted life-year rates worldwide.
The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) is a large-scale study to estimate the cancer burden caused by a broad set of modifiable risk factors. This study estimates the cancer burden over time for all countries across the globe, for all age groups, and for both males and females.
In the current study, scientists analyse the 2019 findings of the GBD study to understand the contributions of modifiable risk factors to the global cancer burden, as well as inform cancer control efforts at regional, national, and global levels.
GBD 2019 broadly includes three types of risk factors, behavioural, environmental and occupational, and metabolic risk factors. A total of 23 cancer types and 34 risk factors are included in the GBD 2019. The GBD 2019 comparative risk assessment framework was utilised to estimate the fraction of the cancer burden caused by each risk factor. A total of 82 cancer risk-outcome pairs were included in the analysis.
Overall, the study estimated risk-attributable cancer-related deaths and disability-adjusted life-years in 2019. Furthermore, the temporal trends of these measures were described between 2010 and 2019.
The total number of cancer deaths caused by all risk factors in 2019 globally was 4.4 million, which accounted for 44.4% of all cancer deaths. The total number of cancer disability-adjusted life years caused by all risk factors in 2019 globally was 105 million, which accounted for 42% of all cancer disability-adjusted life years.
Regarding cancer disability-adjusted life-years, tobacco use is the leading behavioural risk factor in males in 2019, followed by alcohol use, dietary risks, and air pollution. In females, tobacco use was also the leading risk factor associated with cancer disability-adjusted life-years, which was followed by unsafe sex, dietary risks, overweight/obesity, and diabetes.
The risk factors associated with cancer deaths worldwide in 2019 were similar to those associated with cancer disability-adjusted life-years. In both males and females, tracheal, bronchus, and lung cancers were the leading cancers in terms of risk-attributable global cancer mortality in 2019. Other leading cancer types contributing to the global risk-attributable mortality were colon, rectal, oesophageal, and stomach cancers in males, as well as cervical, colon, rectal, and breast cancers in females.
A relatively higher fraction of risk-attributable cancer death was observed in males, compared to females. By excluding gender-specific cancers, smaller male-to-female ratios for risk-attributable cancer deaths were observed in countries with a higher socio-demographic index (SDI), which is a composite index per capita income, educational attainment, and total fertility rate in a country.
The highest number of risk-attributable cancer deaths was observed in high SDI countries in 2019. These measures remained similar when the analysis considered risks attributable to cancer disability-adjusted life-years.
A variation in age-specific risk-attributable cancer deaths and disability-adjusted life-years was observed across the globe, with high-income countries throughout North America and Central, Western, and Eastern Europe showing higher measures. Increased rates of these measures were also observed in east and southeast Asia, southern Latin America, and southern Africa.
About 20% and 16% induction in global rates of risk-attributable cancer deaths and disability-adjusted life-years, respectively, were observed between 2010 and 2019. In contrast, about 6% and 7% reduction in global age-specific rates of risk-attributable cancer deaths and disability-adjusted life-years, respectively, were observed between 2010 and 2019.
Overall, the current study identifies behavioral risk factors as major contributors to the global cancer burden in 2019. However, metabolic risk factors exhibit the highest percentage increase between 2010 and 2019.
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