Oct. 30, 2013 - Men who spend the most time engaged
in sedentary behaviors – a lot of sitting and little exercise - are at
greatest risk for recurrence of colorectal adenomas, benign tumors that
are known precursors of colorectal cancers, according to results
presented here at the 12th Annual AACR International Conference on
Frontiers in Cancer Prevention Research, held Oct. 27-30.
The majority of colorectal cancers arise from
precursors called colorectal adenomatous polyps, or colorectal adenomas,
which can be removed during a colonoscopy. Although there is extensive
evidence supporting an association between higher overall levels of
physical activity and reduced risk of colorectal cancer, few studies
have focused on the impact of sedentary behavior on colorectal cancer
"Sedentary behavior is emerging as a risk factor
for poor health," said Christine L. Sardo Molmenti, PhD, MPH,
postdoctoral research fellow in the Department of Epidemiology at
Columbia University Mailman School of Public Health in New York.
"Even among those who fulfill daily recommendations
for physical activity, lengthy periods of sedentary behavior have been
associated with early morbidity and mortality, leading to the 'active
couch potato' paradigm.
"To our knowledge, this study is the first to
specifically investigate the association between sedentary behavior and
recurrence of colorectal adenomas. Given the substantial increase in
risk of colorectal adenoma recurrence (45%) we observed for men with the
highest sedentary time, we believe it would be beneficial to see 'reduce
prolonged sitting time' added to the list of public health
recommendations currently in place for health promotion and disease
Sardo Molmenti and colleagues performed a pooled
analysis of participants of two randomized, double-blind,
placebo-controlled phase III clinical trials conducted at the University
of Arizona Cancer Center in Tucson and the Mel and Enid Zuckerman
College of Public Health: The Wheat Bran Fiber Study and the
Ursodeoxycholic Acid Trial.
All participants in the trials had one or more
colorectal adenomas removed during a colonoscopy conducted in the six
months prior to their trial enrollment. Among the participants were
1,730 who had completed a self-administered questionnaire that included
questions about leisure, recreational, household, and other categories
of activity at enrollment, and had undergone a follow-up colonoscopy.
When the researchers analyzed all the data
together, they found no association between activity type and colorectal
adenoma recurrence. However, when they examined the data for men and
women separately, they found that men who reported spending more than
11.38 hours a day engaged in sedentary behaviors, such as writing,
typing or working on a computer, and reading, were 45 percent more
likely to experience colorectal adenoma recurrence compared with men who
spent fewer than 6.90 sedentary hours a day. No association between
sedentary time and colorectal adenoma recurrence was observed for women.
Further analysis showed that men who reported high
levels of sedentary behaviors and low levels of participation in
recreational activities such as walking, jogging, and playing golf, were
41 percent more likely to experience colorectal adenoma recurrence
compared with men who reported low levels of both sedentary behaviors
and recreational activity.
According to Sardo Molmenti, this confirms
that sedentary behavior appears to independently contribute to increased
cancer risk beyond the accompanying reduction in physical activity.
The researchers plan to conduct further studies to
determine more clearly the role of sedentary behavior in cancer risk.
According to Sardo Molmenti, new tools and methods are needed to better
classify and quantify sedentary behaviors.
Funding for this study was provided by the National
Institutes of Health and National Cancer Institute. The author has
declared no conflicts of interest.
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