Table 2.

Association between the MTHFR 677C>T polymorphism and migraine, heterogeneity, and publication bias (references are the same for additive, dominant, and recessive models and are only given for the additive models)

Any migraine
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Heterogeneity				Publication Bias
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Q	df	p-value	I² in %	p-value Begg	p-value Egger
additive	All ⁷–¹¹, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	11	1.15 (1.00–1.31)	29.2	10	0.001	66	0.24	0.03
	Caucasian ⁷–¹⁰, ²⁵, ²⁹, ³², ³⁴	8	1.06 (0.95–1.19)	14.0	7	0.05	50	0.62	0.15
	Turkish ²⁶	1	1.80 (1.13–2.87)	----	----	----	----	----	----
	Asian ²⁸	1	1.85 (1.24–2.77)	----	----	----	----	----	----
	Indian ¹¹	1	1.03 (0.64–1.65)	----	----	----	----	----	----
dominant	All ⁷–¹¹, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	11	1.08 (0.96–1.22)	14.1	10	0.17	29	0.24	0.09
	Caucasian ⁷–¹⁰, ²⁵, ²⁹, ³², ³⁴	8	1.00 (0.94–1.06)	5.0	7	0.66	0	1.0	0.48
	Turkish ²⁶	1	1.63 (0.95–2.79)	----	----	----	----	----	----
	Asian ²⁸	1	2.06 (1.15–3.70)	----	----	----	----	----	----
	Indian ¹¹	1	1.14 (0.69–1.87)	----	----	----	----	----	----
recessive	All ⁷–¹⁰, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	10^*	1.39 (1.02–1.90)	32.6	9	<0.0001	72	0.13	0.008
	Caucasian ⁷–¹⁰, ²⁵, ²⁹, ³², ³⁴	8	1.22 (0.92–1.63)	20.8	7	0.004	66	0.32	0.08
	Turkish ²⁶	1	6.31 (1.31–30.41)	----	----	----	----	----	----
	Asian ²⁸	1	2.40 (1.19–4.84)	----	----	----	----	----	----
	Indian	0^*	----	----	----	----	----	----	----
Migraine with aura
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Heterogeneity				Publication Bias
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Q	df	p-value	I² in %	p-value Begg	p-value Egger
additive	All ⁸–¹¹, ²⁵–²⁹, ³², ³⁴, ³⁶	12	1.13 (0.97–1.32)	42.6	11	<0.0001	76	0.41	0.05
	Caucasian ⁸–¹⁰, ²⁵, ²⁷, ²⁹, ³², ³⁴, ³⁶	9	1.08 (0.93– 1.24)	28.5	8	<0.0001	72	0.68	0.13
	Turkish ²⁶	1	1.05 (0.46–2.39)	----	----	----	----	----	----
	Asian ²⁸	1	3.80 (1.88–7.66)	----	----	----	----	----	----
	Indian ¹¹	1	1.06 (0.59–1.90)	----	----	----	----	----	----
dominant	All ⁸–¹¹, ²⁵–²⁹, ³², ³⁴, ³⁶	12	1.03 (0.90–1.18)	19.1	11	0.06	42	0.49	0.14
	Caucasian ⁸–¹⁰, ²⁵, ²⁷, ²⁹, ³², ³⁴, ³⁶	9	1.01 (0.88–1.14)	13.5	8	0.10	41	0.84	0.41
	Turkish ²⁶	1	0.94 (0.39–2.29)	----	----	----	----	----	----
	Asian ²⁸	1	4.20 (1.21–14.54)	----	----	----	----	----	----
	Indian ¹¹	1	1.17 (0.63–2.20)	----	----	----	----	----	----
recessive	All ⁸–¹⁰, ²⁵–²⁹, ³², ³⁴, ³⁶	11^*	1.48 (1.02–2.13)	51.3	10	<0.0001	81	0.48	0.03
	Caucasian ⁸–¹⁰, ²⁵, ²⁷, ²⁹, ³², ³⁴, ³⁶	9	1.28 (0.91–1.80)	36.1	8	<0.0001	78	0.53	0.08
	Turkish ²⁶	1	3.05 (0.27–35.03)	----	----	----	----	----	----
	Asian ²⁸	1	6.54 (2.54–16.81)	----	----	----	----	----	----
	Indian	0^*	----	----	----	----	----	----	----
Migraine without aura
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Heterogeneity				Publication Bias
Genetic model	Population	No of studies	Relative Risk (95% CI)^*	Q	df	p-value	I² in %	p-value Begg	p-value Egger
additive	All ⁸–¹¹, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	10	1.02 (0.89–1.16)	15.5	9	0.08	42	0.33	0.70
	Caucasian ⁸–¹⁰, ²⁵, ²⁹, ³², ³⁴	7	1.00 (0.94–1.06)	5.4	6	0.5	0	0.88	0.30
	Turkish ²⁶	1	2.16 (1.28–3.64)	----	----	----	----	----	----
	Asian ²⁸	1	1.38 (0.86–2.19)	----	----	----	----	----	----
	Indian ¹¹	1	1.01 (0.50–1.75)	----	----	----	----	----	----
dominant	All ⁸–¹¹, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	10	1.04 (0.92–1.17)	10.5	9	0.31	14	0.33	0.77
	Caucasian ⁸–¹⁰, ²⁵, ²⁹, ³², ³⁴	7	1.02 (0.94–1.11)	3.9	6	0.69	0	0.65	0.20
	Turkish ²⁶	1	1.97 (1.09–3.59)	----	----	----	----	----	----
	Asian ²⁸	1	1.63 (0.85–3.13)	----	----	----	----	----	----
	Indian ¹¹	1	1.11 (0.62–2.00)	----	----	----	----	----	----
recessive	All ⁸–¹⁰, ²⁵, ²⁶, ²⁸, ²⁹, ³², ³⁴	9^*	0.94 (0.71–1.23)	12.0	8	0.15	33	0.06	0.66
	Caucasian ⁸–¹⁰, ²⁵, ²⁹, ³², ³⁴	7	0.94 (0.82–1.07)	5.3	6	0.51	0	0.65	0.52
	Turkish ²⁶	1	7.44 (1.50–36.84)	----	----	----	----	----	----
	Asian ²⁸	1	1.23 (0.48–3.17)	----	----	----	----	----	----
	Indian	0^*	----	----	----	----	----	----	----

one study is left out of the analysis ¹¹ because there are no effect estimates (no homozygote TT).