Table 2.

Incidence of MDD in the cholecystectomy and control groups according to age-group classification

Group	n	Event	Person-years	Incidence ratea	HR (95% CI)
					Model 1	Model 2	Model 3
All
Control	223,868	21,401	1,054,969.97	20.2859	1 (Ref.)	1 (Ref.)	1 (Ref.)
Cholecystectomy	111,934	14,022	513,836.6	27.2888	1.367 (1.337, 1.398)	1.367 (1.337, 1.398)	1.339 (1.309, 1.369)
Age, yr
40–49
Control	78,738	4,737	378,576.76	12.5127	1 (Ref.)	1 (Ref.)	1 (Ref.)
Cholecystectomy	39,369	3,500	185,418.03	18.8763	1.533 (1.466, 1.603)	1.533 (1.466, 1.603)	1.508 (1.441, 1.578)
50–59
Control	66,722	9,983	303,187.99	32.9268	1 (Ref.)	1 (Ref.)	1 (Ref.)
Cholecystectomy	33,361	5,979	147,155.52	40.6305	1.251 (1.209, 1.293)	1.251 (1.209, 1.293)	1.217 (1.176, 1.259)
60–69
Control	44,932	5,712	210,631.49	27.1185	1 (Ref.)	1 (Ref.)	1 (Ref.)
Cholecystectomy	22,466	3,587	101,697.13	35.2714	1.329 (1.272, 1.388)	1.329 (1.272, 1.388)	1.295 (1.239, 1.354)
70–79
Control	22,922	4,042	101,318.55	39.894	1 (Ref.)	1 (Ref.)	1 (Ref.)
Cholecystectomy	11,461	2,356	49,247.01	47.8405	1.199 (1.136, 1.266)	1.199 (1.136, 1.266)	1.171 (1.109, 1.237)
≥80
Control	4,268	773	16,764.57	46.1092	1(Ref.)	1(Ref.)	1 (Ref.)
Cholecystectomy	2,134	410	8,473.69	48.3851	1.041 (0.914, 1.186)	1.041 (0.914, 1.186)	0.999 (0.874, 1.141)

CI, confidence interval; HR, hazard ratio; MDD, major depressive disorder.

Model 1: nonadjusted.

Model 2: adjusted for age.

Model 3: adjusted for age, sex, income, place of residence, diabetes mellitus, hypertension, and dyslipidemia.

^aIncidence rate: per 1,000 person-years.