Evidence-Based Answers

Evidence Central™ is an integrated web and mobile solution that helps clinicians quickly answer etiology, diagnosis, treatment, and prognosis questions using the latest evidence-based research.


Instant Savings

Evidence Central iOS iPhone iPad Android

Available on your mobile device and the web, locate answers at the bedside or anywhere they’re needed. Save 10% Today

Word of the Day

Colonoscopy and flex sig associated with lower CRC mortality

Clinical Question:
Are sigmoidoscopy and colonoscopy associated with a decreased likelihood of death due to colorectal cancer?

Bottom Line:
This study found a significant reduction in the number of colorectal cancers (CRCs) and CRC-related mortality in persons who chose to undergo flexible sigmoidoscopy or colonoscopy. This may overestimate the benefit, because of unmeasured confounding (things associated with the decision to have colonoscopy that are also associated with CRC mortality). (LOE = 1b)

Nishihara R, Wu K, Lochhead P, et al. Long-term colorectal-cancer incidence and mortality after lower endoscopy. N Engl J Med 2013;369(12):1095-1105.  [PMID:24047059]

Study Design:
Cohort (prospective)



To date, there have been no randomized trials of screening colonoscopy. These researchers used observational data from the Nurse's Health Study and the Health Professionals Follow-up Study, 2 large prospective cohort trials that has followed women since 1976 and men since 1986, respectively. From 1988 through 2008, participants were asked whether they had undergone screening flexible sigmoidoscopy or colonoscopy. The authors reviewed the medical records and pathology reports of those who reported endoscopy to confirm the presence of polyps or CRC. The National Death Index was used to identify deaths due to any cause and deaths due to CRC. Persons undergoing colonoscopy were similar to those who chose not to have colonoscopy regarding the use of aspirin, multivitamins, alcohol, exercise, and red meat intake. Those who had no lower endoscopy were somewhat younger and were less likely to have a family history of CRC. The analysis adjusted for all of these variables when calculating multivariate hazard ratios for the primary outcomes. The likelihood of dying of CRC was lower among persons who had ever had flexible sigmoidoscopy (adjusted hazard ration [aHR] = 0.59; 95% CI, 0.45 - 0.76) and even lower among those who had ever undergone colonoscopy (aHR = 0.32; 0.24 - 0.45). Colonoscopy reduced the likelihood of death due to both proximal and distal cancers, whereas flexible sigmoidoscopy only reduced the likelihood of distal CRC mortality. The benefit was similar for men and women.


Site Licenses

Site license

Site Licenses are available for schools, universities, hospitals, government agencies, and companies. For more information, contact us.