Cancers among younger adults are a growing global problem
and are likely related to factors like poor diet, obesity
and inactivity, a new research review finds. Since the
1990s, researchers say, rates of various cancers have been
rising in many countries among people under 50. And while
the reasons are not fully clear, it's likely that changes in
lifestyle and environment — starting early in life — are
playing a role. The review found that in recent decades,
rates of 14 cancers have been inching up annually among
younger adults in a diverse range of countries — from the
United States and Canada, to Sweden and England and to
Ecuador, Uganda and South Korea. The cancers, similarly, run
the gamut, and include those of the breast, colon,
esophagus, kidneys, liver, stomach and pancreas. For certain
cancers, increased screening may partly explain the rising
incidence, according to researcher. Screening tests for
diseases like breast and colon cancers can detect more
cases, at an earlier point in time. But for the most part,
he said, the growing cancer incidence among younger adults
is beyond what would be expected from heightened detection.
And many of the cancers that are increasing arise along the
digestive tract — "anywhere from the mouth to the anus," he
said. That, he added, points to a potential role for the
microbiome. The microbiome refers to the vast array of
bacteria that normally dwell in the body, largely the
digestive tract. Research in recent years has been revealing
how important the microbiome is to overall health, playing a
role in immunity, fighting chronic inflammation and other
vital functions. For any one person, makeup of the
microbiome depends partly on genes. But he noted that
environmental factors are critical, too — including diet,
alcohol intake, smoking, exercise and antibiotic use. And
many of those environmental exposures have shifted
substantially in recent decades. The spread of the
"westernized" diet is a clear example, he said. It's high in
heavily processed foods, added sugar and red meat, but low
in fruits, vegetables, fiber and "good" fats — qualities
that have been linked to increased risks of certain cancers,
like colon cancer. The rise in colon cancers among younger
adults has been gaining particular attention. According to
the U.S. National Cancer Institute, the incidence of that
disease among Americans younger than 50 has more than
doubled since the 1990s — in sharp contrast to a decrease
among people older than 65. In fact, the trend spurred
experts to lower the recommended starting age for colon
cancer screening. It's now age 45 for people at average risk
of the disease. Obesity among children and younger adults
has, of course, skyrocketed in recent years. And on the
opulation level, researcher said, there is a relationship
between obesity and colon cancer risk. But many younger
people who are diagnosed with the disease are not obese, and
the reasons behind the rising incidence would appear to go
beyond a single factor. Much more research is needed to
understand what's driving the rise in various early-onset
cancers, researcher said. |