Table 1. Relative risk and 95% confidence intervals for different subgroups of studies.

Subgroup of studies	Relative risk	Lower 95% CI	Upper 95% CI	number of studies	p-value for comparison
Case-control	2.11	1.82	2.43	14	0.39
Cohort	2.33	1.96	2.78	4
Definite MS	2.12	1.69	2.64	5	0.74
Definite/probable MS	2.21	1.97	2.47	10
Latitude <54	2.01	1.51	2.67	9	0.56
Latitude ≥54	2.2	1.96	2.47	9
Sex-ratio <2.12	2.03	1.54	2.67	7	0.61
Sex-ratio ≥2.12	2.21	1.85	2.63	8

P-values for comparison between subgroups are also shown.