时间（月）

Native(n=115)

Non-Native(n=30)

P value

<=12

1(0.9%)

1(3.3%)

0.729a

13-24

12(10.4%)

2(6.7%)

25-36

21(18.3%)

3(10.0%)

37-48

20(17.4%)

7(23.3%)

49-60

23(20.0%)

9(30.0%)

61-72

14(12.2%)

1(3.3%)

73-84

9(7.8%)

2(6.7%)

85-96

9(7.8%)

3(10.0%)

>96

6(5.2%)

2(6.7%)