Table 1.

Examples of large-scale observational epidemiological studies and meta-analyses on the effects of screening colonoscopy reported since 1993

Authors, year (reference)	Study	Relative risk (95% CI)
		CRC Incidence	CRC mortality
Winawer et al. 1993 [5]	US National Polyp Study	0.24a, p < 0.001 0.12b, p < 0.001
Nishihara et al. 2013 [8]	Nurses' Health Study and Health Professionals Follow-up Study		0.18 (0.10–0.31)
Brenner et al. 2014 [9]	Meta-analysis	0.31 (0.12–0.77)	0.32 (0.23–0.43)
Stock et al. 2016 [10]	Population-wide Canadian cohort		0.36 (0.33–0.38)
Doubeni et al. 2018 [11]	Kaiser Permanente members, US		0.33 (0.21–0.52)
Guo et al. 2021 [12]	ESTHER cohort study, Germany	0.44 (0.33–0.57)	0.34 (0.21–0.53)

^aComparison of a cohort with colonoscopic polypectomy with the general population (in which screening colonoscopy was uncommon during the period of investigation); given the inherently increased risk of people with polyps, this comparison underestimates the effects that would have be obtained by comparing an entire screening colonoscopy cohort with the general population

^bComparison of a cohort with colonoscopic polypectomy with a retrospective cohort of participants with colonoscopy-detected but unremoved polyps