It is not entirely clear why bowel cancer is increasing among adults under 50
STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY
Intestinal rates cancer has increased among younger adults in countries around the world, although the trend appears to be most common in high-income nations.
Previous studies have shown that it is intestinal or colorectal cancer rates have increased in this age group in recent decades in several Western countries, including the USA, Canada, Australia and the UK. This has led to speculation that Western lifestyles, such as diets high in meat or processed foods, may be to blame.
To better understand the extent of the problem, Hyun Sung At the American Cancer Society in Atlanta, Georgia, he and his colleagues analyzed bowel cancer rates in 50 countries and territories around the world. In general, they collected data on its incidence from 1975 to 2017 using a World Health Organization database, although some countries did not start collecting this information until several years after 1975.
The team found that rates of bowel cancer in people aged 25 to 49 had increased in 27 countries and territories. Among others, non-Western countries such as Japan and less affluent nations such as Turkey raise the possibility that Western lifestyles alone are not behind this trend.
The increase is also unlikely to be related to improvements in screening, as most countries do not routinely test people with bowel cancer until they are 50, the researchers wrote.
However, all 27 countries and territories score high or very high on the United Nations’ Human Development Index, which is based on average life expectancy, educational attainment and per capita income.
Also, all but six are considered high-income, according to the World Bank. Unlike most of the high-income nations studied, in these six places bowel cancer increased among older adults, equal to or greater than among younger adults.
“I think there is still evidence that economic development and the westernization of lifestyles play a role in the trends,” he says. Andrew Chan Harvard University notes that many countries are adopting aspects of this lifestyle as their economies grow. For example, meat intake in Japan increased more than seven times between 1961 and 2021.
“That said, I think it should still be considered that there are probably other factors at play,” such as environmental pollutants, Chan says.
The researchers note that their study has several limitations, the most obvious being that African and Asian countries and small islands were represented. Only one African nation – Uganda – was included, for example. Some countries also did not have complete data sets. For example, the data for India was only representative of 4% of the population there.
However, these findings improve our understanding of how bowel cancer rates vary between many countries, which could help us devise new ways to prevent the disease, Chan says.
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