Cholecystectomy and the risk of alimentary tract cancers: A systematic review

Table 1 Descriptive characteristics of studies on the association between cholecystectomy and oesophageal adenocarcinoma

Ref.	Period of study	Study design	No. of cases	No. of controls	Exposure ascertainment	Outcome ascertainment	Follow-up (yr)	Effect estimate	Adjustments	Quality of publication
Freedman et al[20], 2000	1994-1997	Case-control	189	820	Self report	Pathology records	-	RR = 1.03 (0.63-1.69)	Age, gender, alcohol, smoking, BMI, physical activity, education, diet	37
Nogueira et al[21], 2014	1992-2005	Case-control	132/5488	2572/1000000	Medicare database	Cancer registry	> 6	OR = 0.95 (0.80-1.14)	Age, gender, diabetes	49
Freedman et al[23], 2001	1965-1997	Cohort	53/268312		National registry	Cancer registry	> 10	SIR = 1.3 (1.0-1.8)	Age, gender	38
Goldacre et al[22], 2005	1963-1999	Cohort	91/39245	803/334813	NHS database	Cancer registry	NA	RR = 0.98 (0.79-1.21)	Age, gender, calendar year, residence	36
Lagergren and Mattsson[24], 2011	1965-2008	Cohort	126	345251	NA	Cancer registry	15	RR = 1.29 (1.07-1.53)	Age, gender, calendar Year	40

NA: Not available; BMI: Body mass index.