Table 3. Association of patient- and study-factors on the mean difference in IIEF-EF comparing antioxidant to placebo groups.

Variable	Z-scorea	p-value
		Univariable	Multivariable
Lower baseline IIEF-EF score	3.73	<0.001	<0.001
Longer treatment duration	2.51	0.01
Larger sample size	1.85	0.07
Crossover vs. parallel	0.80	0.43
Older age	0.32	0.75

IIEF-EF: International Index of Erectile Function-Erectile Function.

^aPositive z-value indicates the variable improved the overall benefit of antioxidant supplementation.