Table 1.

Comparison of the general data among PCN, PCD and PCDN groups (χ ± s)

Group	Y/A (years of age)	Number	Sex		Follow-up time (years)	Level
			Male	Female		C3–4	C4–5	C5–6	C6–7
PCD	47.8 ± 10.8	97	53	44	4.2	5	22	41	30
PCN	48.5 ± 9.4	50	29	21	2.6	2	18	24	6
PCDN	46.5 ± 10.4	24	15	9	3.3	1	5	17	0
Statistic analyses	F = 0.267 P = 0.766		χ 2 = 0.531 P = 0.767		χ 2 = 1.9 P = 0.387	χ 2 = 18.61, P = 0.003