Association between 𝜺2/3/4, Promoter Polymorphism (−491A/T, −427T/C, and −219T/G) at the Apolipoprotein E Gene, and Mental Retardation in Children from an Iodine Deficiency Area, China

Table 1

Population characteristics according to case and control.

	County	𝑁	Sex ratio (F : M)	Mean age ± SD
Control	Zhashui	250	117/133	9.3±2.8
	Ankang	84	37/47
Border^a	Zhashui	80	42/38	10.2±2.9
	Ankang	44	22/22
MR^b	Zhashui	73	38/35	10.1±2.8
	Ankang	57	27/30
Sum		588	283/305	9.7±2.9

aBorderline mental retardation (border) group.
^bMental retardation (MR) group.