Distribution of MTHFR C677T polymorphism among populations from 10 regions in Chinaa.

Abbreviation: MTHFR, methylenetetrahydrofolate reductase; CC, “wild-type” homozygosity; CT, heterozygosity; TT, mutant homozygosity; CI, confidence interval.aThe 10 regions include 9 provinces (Shandong, Henan, Shannxi, Jiangsu, Hubei, Yunnan, Guangdong, and Hainan) and 1 municipality (Tianjin).bThe 677T allele frequencies were significantly different among the 10 populations (χ2 = 2166.61, PcThe 677TT genotype frequencies were significantly different among the 10 populations (χ2 = 1242.20, P*The 677T allele frequencies were significantly different from the southern populations (χ2 = 6.55, P = 0.0105).#The 677TT genotype frequencies were significantly different from the southern populations (χ2 = 6.59, P = 0.0103).