May 19, 2016 / 5:50 PM
CDT / Updated May 19, 2016 / 5:50 PM CDT
By Maggie Fox
As many
as 40 percent of cancer cases, and half of cancer deaths, come down to things
people could easily change, researchers said Thursday.
While
Americans often worry about whether chemicals, pollution or other factors out
of their control cause cancer, the new analysis shows otherwise: People are
firmly in charge of much of their own risk of cancer.
The
team at Harvard Medical School calculated that 20 to 40 percent of cancer
cases, and half of cancer deaths, could be prevented if people quit smoking,
avoided heavy drinking, kept a healthy weight, and got just a half hour a day
of moderate exercise.
They
used data from long-term studies of about 140,000 health professionals who
update researchers on their health every two years for the analysis, published
in the Journal of the American Medical Association’s JAMA
Oncology.
“Not
surprisingly, these figures increased to 40 percent to 70 percent when assessed
with regard to the broader U.S. population of whites, which has a much worse
lifestyle pattern than our cohorts,” Dr. Mingyang Song and Dr. Edward
Giovannucci of Harvard Medical School wrote.
The
analysis was simple. They broke the 140,000 people into two groups: those with
a healthy lifestyle, and everyone else.
The
healthy lifestyle definition was based on a large body of studies that have
shown what personal habits are linked with higher or lower risks of cancer.
"A
large proportion of cancers are due to environmental factors and can be
prevented by lifestyle modification.”
They
include not smoking; drinking no more than one drink a day for women, two
drinks a day for men; keeping a healthy weight, defined as body mass index of
between a very slender 18.5 and a slightly overweight 27.5; and getting the
equivalent of just over an hour of vigorous exercise or two and a half hours of
moderate exercise a week.
Heavy
drinking raises colon, breast, liver and head and neck cancer rates. Obesity
raises the risk of esophageal, colon, pancreatic and other cancers. Smoking
causes 80 to 90 percent of lung cancer deaths.
Only
about 28,000 of the people qualified as following a healthy lifestyle. When the
rates of cancer in their group were compared to rates in the rest of the
volunteers, the differences were clear.
The
incidence rates of cancer were 463 per 100,000 for women in the “healthy”
group, versus 618 per 100,000 for those not meeting the healthy goals. For men,
it was 283 per 100,000 who met the healthy lifestyle goals versus 425 among
those who did not.
And
these were health professionals, who should at least try to be healthier. When
Song and Giovanucci compared the healthy group to the general, white, U.S.
public, the differences were even bigger.
Their
findings are not mean to be exact, and they did fudge a little. “We excluded
from all cancers those in the skin, brain, lymphatic, and hematopoietic (blood
and bone marrow) tissues because these cancers likely have other strong
environmental causes than the ones considered in the current study, such as UV
exposure, infections, irradiation, and exposures to carcinogenic substances,”
they wrote.
And
they didn’t add in other known factors, such as eating a healthy diet rich in
fruits and vegetables – although they said those who followed the other healthy
patterns did tend to eat better, also.
"These
compelling data together with the findings of the current study provide strong
support for the argument that a large proportion of cancers are due to environmental
factors and can be prevented by lifestyle modification." By
"environmental," they mean non-genetic causes. To a scientist,
environment includes diet, exercise and other factors.
“Cancer
is preventable,” Dr. Graham Colditz and Dr. Siobhan Sutcliffe of Washington
University School of Medicine in St. Louis agreed in a commentary.
"It
is important to consider actions such as cigarette taxes; subsidies on fruits,
vegetables, and whole grains; quality physical education in schools."
“In
fact, most cancer is preventable—with estimates as high as 80 percent to 90
percent for smoking-related cancers, such as lung and oropharyngeal cancer, and
as high as 60 percent for other common, lifestyle-related cancers, such as
colorectal and bladder cancer.”
They
said health insurance companies, medical societies and regulators should
encourage doctors to help their patients do what they need to do to prevent
cancer, the No. 2 cause of death in the United States.
“Guidelines
and reimbursement structures should foster patient counseling on being more
active, cutting back on screen time, eating a plant-based diet, keeping weight
in check, and getting vaccinated,” they wrote.
“The
broader physical communities in which people live can also help support and
build on health behaviors. Efforts here can focus on things like farmers’
markets in underserved neighborhoods, safe and affordable places for people to
exercise, and buildings that help foster activity,” they added.
“Finally,
from a policy perspective, it is important to consider actions such as
cigarette taxes; subsidies on fruits, vegetables, and whole grains; quality
physical education in schools; and more broadly, efforts to reduce income
disparity, which is a major cause of cancer disparities.”
They
said Americans need to stop thinking that cancer is down to bad luck or a
result of factors out of their control.
"Instead
we must embrace the opportunity to reduce our collective cancer toll by
implementing effective prevention strategies and changing the way we
live."
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