Table 3.

Cox proportional hazards analysis.

	Hazard ratio (95% CI)	P-value
No IA-HA*	–	–
1 Course	0.85 (0.84–0.86)	<.0001
2 Courses	0.55 (0.54–0.57)	<.0001
3 Courses	0.43 (0.41–0.45)	<.0001
4 Courses	0.36 (0.34–0.38)	<.0001
5+ Courses	0.27 (0.25–0.28)	<.0001

^*Reference group.