Table 3.

Incidence rate, hazard ratio of breast cancer in different stratification.

	Comparison			Non-lactational mastitis			Non-lactational mastitis vs Comparison
	n = 12364			n = 3091			Crude HR	Adjusted HR
	Event	Person years	IR	Event	Person years	IR	(95% CI)	(95% CI)
Overall	74	97722	7.57	37	25010	14.79	1.94 (1.31–2.87)**	1.94 (1.30–2.90)**
Age at baseline
<40	26	62439	4.16	16	16168	9.90	2.36 (1.27–4.4)**	2.22 (1.18–4.18)*
40–49	28	21294	13.15	14	5245	26.69	2.00 (1.05–3.81)*	2.12 (1.11–4.04)*
50–59	14	9061	15.45	4	2454	16.30	1.03 (0.34–3.12)	1.28 (0.41–4.02)
≥60	6	4928	12.18	3	1143	26.25	2.21 (0.55–8.84)	1.80 (0.43–7.48)
Monthly income (NT$)
0–15840	23	51975	4.43	15	12952	11.58	2.63 (1.37–5.04)**	2.60 (1.34–5.07)**
15841–28800	36	33946	10.61	16	8886	18.01	1.66 (0.92–3.00)	1.68 (0.93–3.06)
28801–45800	9	9125	9.86	5	2420	20.67	2.05 (0.69–6.12)	2.02 (0.66–6.16)
>45800	6	2676	22.42	1	753	13.29	0.59 (0.07–4.86)	0.53 (0.06–4.99)
Baseline comorbidity
Schizophrenia	5	2227	22.46	1	622	16.07	0.67 (0.08–5.76)	0.84 (0.09–7.60)
Hypertension	12	9988	12.01	6	2997	20.02	1.60 (0.60–4.27)	1.63 (0.60–4.42)
Chronic obstructive pulmonary disease	11	9861	11.16	5	2766	18.07	1.61 (0.56–4.65)	1.39 (0.47–4.05)
Thyroid disease	5	7414	6.74	1	2144	4.66	0.67 (0.08–5.72)	0.61 (0.07–5.47)
Diabetes	10	7023	14.24	3	1913	15.68	1.08 (0.30–3.91)	1.05 (0.28–3.85)
Hyperlipidemia	14	11089	12.63	5	3099	16.13	1.24 (0.45–3.46)	1.16 (0.41–3.25)
Obesity	0	1064	0.00	0	320	0.00	—	—
Medication
Hormonal medication	33	45423	7.27	23	16143	14.25	1.93 (1.13–3.28)*	1.96 (1.15–3.34)*

*Abbreviation: IR, incidence rates, per 10,000 person-years; HR, hazard ratio; CI, confidence interval.

*Adjusted HR: adjusted for age, income, comorbidities and medication in Cox proportional hazards regression.

*p-value < 0.05 *p-value < 0.01**.