Risk of anemia in morbidly obese patients after bariatric surgery in Taiwan

Table 3 Incidence rate and hazard ratio with 95% confidence intervals of anemia associated with receiving bariatric surgery, stratified by sex and age

Variable	Receiving bariatric surgery						Receiving vs not-receiving bariatric surgery
	No			Yes			Crude HR	Adjusted HR2
	Event	Person years	IR1	Event	Person years	IR1
Total	38	6359	5.98	183	16277	11.24	1.71(1.20-2.44)b	2.36(1.52-3.65)c
Gender
Female	27	3455	7.82	159	10688	14.88	1.67(1.10-2.53)a	2.48(1.50-4.09)c
Male	11	2905	3.79	24	5588	4.29	1.24(0.60-2.55)	2.04(0.89-4.70)
Age group, yr
20-29 yr	4	1386	2.89	84	7825	10.73	3.11(1.14-8.54)a	3.83(1.13-12.99)a
30-64 yr	27	4341	6.22	99	8446	11.72	1.81(1.18-2.79)b	2.37(1.45-3.88)c
65-100 yr	7	632	11.07	0	6	0	-	-

¹IR: Incidence rates, per 1000 person-years.

²Represented adjusted hazard ratio: Mutually adjusted for sex, age, receiving bariatric surgery, and baseline comorbidities (as like tables) in Cox proportional hazard regression.

^aP < 0.05.

^bP < 0.01.

^cP < 0.001. HR: Hazard ratio.