Table 2. Overall and age-specific incidence densities and relative hazards of breast cancer (ICD-9∶174) in the diabetes and control groups.

	Control Group			Diabetes Group			Crude HR (95% CI) in association with diabetes group	Adjusted HR† (95% CI) in association with diabetes group
	No. of subjects	No. of events	ID* (per 10,000 patient-years) (95% CI)	No. of subjects	No. of events	ID* (per 10,000 patient-years) (95% CI)
Age (years)
20–49	55602	562	1.15(1.06–1.25)	55601	536	1.14(1.05–1.24)	0.99(0.88–1.12)	1.16(1.02–1.31)
50–64	128389	1311	1.17(1.11–1.24)	128389	1432	1.37(1.30–1.44)	1.17(1.09–1.26)	1.40(1.29–1.51)
≧65	135317	783	0.74(0.69–0.80)	135318	977	1.05(0.99–1.12)	1.41(1.28–1.55)	1.61(1.45–1.78)
Total	319308	2656	1.00(0.96–1.04)	319310	2945	1.21(1.16–1.25)	1.21(1.15–1.28)	1.42(1.34–1.50)

ID, incidence density; CI, confidence interval; HR, hazard ratio; AHR, adjusted hazard ratio.

^*Based on Poisson assumption.

^†Based on Cox proportional hazard regression with adjustment for age, geographic area, urbanization status, Charlson’s score, history of hypertension, endometriosis, and abortion, and frequency of medical visit.