Data published in The Lancet on 20 August, largely confirm results from smaller studies and highlight how reducing exposure to risk factors could help to prevent a substantial proportion of cancers
The take-home message is simple: “Don’t smoke,” says Kaaks. “Don’t get overweight, and don’t drink too much alcohol.”
Heavy burden
The true number of cancer cases and deaths worldwide is hard to pin down, because some countries do not record such data. To overcome this, researcher used data from a study looking at death and disability from more than 350 diseases and injuries in 204 countries. From those data, they estimated the impact of 34 risk factors on poor health and deaths from 23 types of cancer.
In 2019, half of all male deaths from cancer, and more than one-third in women, were due to preventable risk factors including tobacco and alcohol use, unhealthy diets, unsafe sex and workplace exposure to harmful products, such as asbestos.
From 2010 to 2019, global cancer deaths caused by these risk factors increased by about 20%, with excess weight accounting for the largest percentage of increase — particularly in lower income nations.
Smoke-free policies, increased taxes on tobacco and advertising bans have proved effective in diminishing exposure to smoking, and similar efforts have been recommended to help reduce excess alcohol use.
Future research
The study did not include some other known risk factors for cancer, including exposure to ultraviolet (UV) radiation and certain infections. Although the researchers used ‘unsafe sex’ as a proxy for cancer risks associated with human papillomavirus (HPV) and other sexually transmitted viruses. Cervical cancer, which is caused by certain strains of HPV, is the leading cause of cancer deaths among women in sub-Saharan Africa.
The team might include risk factors such as infections and exposure to UV radiation in future analyses
Future work could help to evaluate the effects of the COVID-19 pandemic on cancer cases and deaths. A 2020 study2 estimated that, by 2025, there will be more than 3,000 avoidable cancer deaths in England as a result of diagnostic delays because of COVID-19.
In some areas, researchers say, the pandemic might have changed people’s exposure to certain risk factors: for example, workplace exposure to harmful products might have decreased during lockdowns. However, potential changes in risk-factor exposures and the impact on future cancer burden will likely take many years to comprehensively understand.
References
GBD 2019 Cancer Risk Factors Collaborators. The global burden of cancer attributable to risk factors, 2010-19: a systematic analysis for the Global Burden of Disease Study 2019. Lancet. 2022 Aug 20;400(10352):563-591. doi: 10.1016/S0140-6736(22)01438-6. PMID: 35988567; PMCID: PMC9395583.