Characteristic | Cases (n = 253) | Controls (n = 253) | Test statistic ( P-value)* | ||
---|---|---|---|---|---|
Quantitative or ordinal variables | |||||
Age (year, mean ± SD) | 19.6 ± 1.17 | 19.6 ± 1.15 | 0.53 (0.594) | ||
BMI (kg/m2, mean ± SD) | 20.3 ± 2.56 | 20.2 ± 2.41 | 0.33 (0.744) | ||
Annual per-capita income, Yuan | 0.77 (0.442) | ||||
<2000 | 30 (11.9%) | 30 (11.9%) | |||
2000 ~ 10000 | 59 (23.3%) | 73 (28.9%) | |||
10000 ~ 30000 | 83 (32.8%) | 71 (28.1%) | |||
30000 ~ 50000 | 36 (14.2%) | 41 (16.2%) | |||
> 50000 | 45 (17.8%) | 38 (15.0%) | |||
Dichotomous variables | |||||
Exposure in pair† | |||||
Both positive | Only in case | Only in control | Both negative | ||
No. of siblings | 44 | 62 | 59 | 88 | 0.514 |
Smoke | 0 | 4 | 12 | 237 | 0.057 |
Drink | 0 | 4 | 14 | 235 | 0.027 |
Sports | 125 | 61 | 35 | 32 | 0.009 |
Club activity | 96 | 69 | 48 | 40 | 0.054 |