Mortality rates from cancers and cardiovascular disease (CVD) are declining in most highly developed countries, largely due to programmes of effective prevention, early detection, and treatment.
In contrast, cancer mortality rates are still rising or at best stabilising in less resourced countries.
An international team of researchers, led by Bochen Cao at the International Agency for Research on Cancer (IARC) in Lyon, France, assessed the impact of cancer compared with CVD on life expectancy in people aged 40-84, or the expected number of years lived between 40 and 84 years old, worldwide from 1981 to 2010.
The researchers used mortality data from the national civil registration systems of 52 countries for all cancers combined, as well as the five most common causes of cancer deaths: lung, colorectal, stomach, prostate and breast cancer.
Populations were grouped by two levels of the Human Development Index (HDI), a social indicator, which measures national wellbeing in terms of wealth, health, and education. Other causes of death were taken into account.
The analysis shows that declines in mortality rates from CVD were responsible for over half of the gains in life expectancy in ages 40-84 between 1981 and 2010, with gains of 1.7 years in women and 2.3 years in men in very high HDI populations.
The contribution from cancer was much smaller, at up to one fifth of gains in life expectancy in ages 40-84, and varied depending on the level of development, with gains of 0.5 years in women and 0.8 years in men in very high HDI populations, and 0.2 years for both sexes, in medium and high HDI populations.
A decline in lung cancer mortality rates due to tobacco control measures, brought about the largest gain in life expectancy in ages 40-84 in men in very high HDI populations (up to 0.7 years in the Netherlands), whereas in medium and high HDI populations its contribution was smaller yet still positive.
In contrast, increasing lung cancer mortality rates reduced life expectancy in ages 40-84 in women in many very high HDI populations (up to 0.3 years in the Netherlands).
Among women, declines in breast cancer mortality rates were largely responsible for the improvement in longevity, particularly among very high HDI populations (up to 0.3 years in the UK), largely due to interventions such as early detection, improved diagnosis, and better access to effective treatment.
In contrast, losses in life expectancy in ages 40-84 were observed in many medium and high HDI populations as a result of increasing breast cancer mortality rates.
The authors say their findings are of great relevance to populations in low and middle income countries, calling for resources, “To be urgently allocated to the development and implementation of effective, affordable, feasible, and sustainable cancer control measures in countries undergoing socioeconomic and health transitions.”
Global inequality in longevity gains reflects inequities in cancer control, said Marie Louise Tørring from Aarhus University in a linked editorial. She questions whether rich countries “Will eventually reach a ceiling where their economic and social power is no longer enough to overcome cancer as a natural break on the human lifespan.”
But while even rich countries may fail to control cancer as their populations grow older, “There is plenty that can be done now about current inequities in cancer control, including priority funding for poorer countries and for women,” Tørring writes.
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