Table 3. MS incidence based on region, gender, provinces, year of study and design.

Variable		Studies (N)*	Sample (N)		Heterogeneity		95% CI	Pooled (Per 100,000)
			MS	All	I2	P-Value
Region	Center	26	41134	284522333	99.97	< 0.001	2.0–7.6	3.9
	East	4	94	9227079	67.80	0.025	0.7–1.4	1.0
	South	4	1002	17860233	98.43	< 0.001	2.9–8.2	4.9
	Test for subgroup differences: Q = 28.94, df(Q) = 2, P< 0.001
Gender	Male	31	2158	136555427	99.87	< 0.001	1.0–1.4	1.2
	Female	31	76156	75432131	99.87	< 0.001	39.3–59.1	48.2
	Rate ratio of female to male: OR = 3.04 (2.85–3.24, P< 0.001)
Province	Fars	3	908	13585254	97.40	< 0.001	4.2–9.6	6.3
	Isfahan	2	574	8802567	98.81	< 0.001	2.4–13.5	5.7
	Khuzestan	1	94	4274979	-	-	1.8–2.7	2.2
	Sistan and Balouchestan	4	94	9227079	67.80	0.025	0.7–1.4	1.0
	Tehran	24	40560	275719766	99.97	< 0.001	1.8–7.6	3.7
	Test for subgroup differences: Q = 49.07, df(Q) = 4, P< 0.001
Year of study	< 1990	1	60	8769776	-	-	0.5–0.9	0.7
	1990–1994	5	586	47222144	93.90	< 0.001	0.8–1.6	1.2
	1995–1999	5	1402	53251981	79.37	< 0.001	2.3–2.9	2.6
	2000–2004	6	2919	65291907	90.76	< 0.001	3.9–5.0	4.4
	2005–2009	11	3474	76707337	98.09	< 0.001	2.2–3.7	2.8
	2010–2014	5	13887	46925376	99.96	< 0.001	2.0–56.7	10.6
	2015–2018	1	19902	13441124	-	-	146.0–150.1	148.1
	Test for subgroup differences: Q = 10943.73, df(Q) = 6, P< 0.001
Study design	Population based	27	41468	289305020	98.66	< 0.001	2.0–7.7	4.0
	Cross-sectional	7	762	22304625	99.97	< 0.001	0.9–3.8	1.8
	Test for subgroup differences: Q = 2.38, df(Q) = 1, P = 0.123

N: Number; CI: confidence interval

* Some studies have been included and estimated the prevalence for more than 1 year and also regions. Each data was considered separately because of assessing the slope of prevalence in the years and estimating which region is the highest or lowest.