Comparison 3. Subgroup analysis: nifedipine versus placebo by RP type.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Frequency of attacks: nifedipine vs placebo by RP type	9	268	Mean Difference (Fixed, 95% CI)	‐4.34 [‐5.09, ‐3.59]
1.1 Nifedipine vs placebo for primary RP	6	148	Mean Difference (Fixed, 95% CI)	‐4.42 [‐5.35, ‐3.50]
1.2 Nifedipine vs placebo for secondary RP	6	120	Mean Difference (Fixed, 95% CI)	‐4.19 [‐5.47, ‐2.91]
2 Severity of attacks: nifedipine vs placebo by RP type	4	108	Mean Difference (Fixed, 95% CI)	‐0.82 [‐1.07, ‐0.58]
2.1 Primary RP	2	54	Mean Difference (Fixed, 95% CI)	‐1.74 [‐2.09, ‐1.39]
2.2 Secondary RP	3	54	Mean Difference (Fixed, 95% CI)	0.01 [‐0.32, 0.34]