Folate Intake, MTHFR Polymorphisms, and the Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis

Table 3

Subgroup analysis for the MTHFR A1298C polymorphism.

	Number of studies	Number of participants in case/control		Summary effect estimate	95% CI	Tests for heterogeneity
		AA genotype	Comparator genotype
Subgroup by location
Asian countries							𝐼 (%)
AC versus AA	15	1,727/3,047	991/1,615	0.99	0.84–1.16	χ² = 26.56, df = 14 (P = 0.02)	47
CC versus AA	14*	1,727/3,047	116/178	0.72	0.55–0.93	χ² = 14.37, df = 13 (P = 0.35)	10
European countries
AC versus AA	14	2,971/4,119	2,404/3,746	1.05	0.97–1.14	χ² = 14.78, df = 13 (P = 0.32)	12
CC versus AA	14	2,971/4,119	683/908	1.14	1.01–1.28	χ² = 13.13, df = 13 (P = 0.44)	1
USA
AC versus AA	7	1,678/2,694	1,365/2,244	0.99	0.88–1.11	χ² = 7.96, df = 6 (P = 0.24)	25
CC versus AA	7	1,678/2,694	247/559	0.73	0.57–0.92	χ² = 10.20, df = 6 (P = 0.12)	41
Subgroup by control
Hospital controls
AC versus AA	12	1,872/2,795	1,258/1,874	1.05	0.95–1.16	χ² = 4.42, df = 11 (P = 0.96)	0
CC versus AA	12	1,872/2,795	232/311	1.12	0.88–1.42	χ²= 13.22, df = 11 (P = 0.28)	17
Healthy controls
AC versus AA	27	5,083/7,939	3,926/6,325	1.02	0.93–1.11	χ²= 48.87, df = 26 (P = 0.004)	47
CC versus AA	26*	5,083/7,939	912/1,439	0.88	0.76–1.03	χ²= 45.33, df = 25 (P = 0.008)	45

*There was one study that had no results for this genotype.