A self-controlled case series to assess the effectiveness of beta blockers for heart failure in reducing hospitalisations in the elderly

Table 2 Case-series adjusted analysis for 1 year observation period

Risk Periods	Number of Hospitalisations	Person-Years	Adjusted age and study month only RR(95% CI)	Adjusted* RR(95% CI)
Baseline unexposed Period
Unexposed	3275	2660	1.00 (1.00 - 1.00)	1.00 (1.00 - 1.00)
Pre-exposure to a beta blocker for heart failure
6-8 weeks	18	22	1.37 (0.93 - 2.01)	1.29 (0.88 - 1.89)
4-6 weeks	52	23	3.74 (2.90 - 4.82)	3.47 (2.70 - 4.46)
2-4 weeks	87	24	5.85 (4.72 - 7.26)	4.97 (4.02 - 6.16)
1 day-2 weeks	255	25	15.98 (13.51 - 18.91)	12.72 (10.74 - 15.07)
Post-exposure to a beta blocker for heart failure
1 day-2 weeks	46	25	2.85 (2.18 - 3.72)	2.21 (1.70 - 2.88)
2-4 weeks	25	23	1.63 (1.16 - 2.29)	1.29 (0.92 - 1.80)
1-4 months	94	107	1.34 (1.08 - 1.67)	1.18 (0.94 - 1.47)
4-8 months	46	76	0.78 (0.58 - 1.04)	0.76 (0.57 - 1.02)
8-12 months	15	24	0.66 (0.42 - 1.05)	0.62 (0.39 - 0.99)

*Adjusted for age at heart failure hospitalisation[8], study month and time-varying covariates which were assessed quarterly; co-morbidities using the Australian adaption of Rx-Risk-V[19], number of prescribers, admission into aged care and prescription of frusemide, ACE/A2RB, digoxin and aldosterone antagonists