Table 1. Characteristics of the gallstone cohort (consisting of patients with a gallstone diagnosis who did not undergo cholecystectomy in Sweden) and characteristics of the cholecystectomy cohort (consisting of patients who underwent cholecystectomy) in Sweden between 1965 and 2008.

	Gallstone cohort			Cholecystectomy cohort
	Men	Women	Total	Men	Women	Total
No. of individuals (%)	75 116 (38.9)	117 844 (61.1)	192 960	114 898 (33.3)	230 353 (66.7)	345 251
Number of person-years at risk	498 080	942 767	1 440 848	1 418 031	3 436 938	4 854 969
Median age at entry	69.7	66.6	68.1	57.8	50.4	53.2
Average year of entry	1992	1992	1992	1988	1988	1988
Median follow-up time in years (interquartile range)	5.6 (2.2–12.0)	7.0 (2.7–13.8)	6.4 (2.5–13.2)	10.5 (4.9–20.2)	13.2 (6.0–24.8)	11.9 (5.6–23.3)
Number of cases with intrahepatic cholangiocarcinoma (%)	32 (45.7)	40 (54.3)	72	50 (51.0)	48 (49.0)	98
Median age at diagnosis	70.2	75.9	72.0	71.2	70.6	71.2
Number of cases with extrahepatic cholangiocarcinoma (%)	75 (44.4)	94 (55.6)	169	94 (41.4)	133 (58.6)	227
Median age at diagnosis	75.1	75.6	75.1	72.0	71.9	71.9