Table 1 Comparison of demographics and socioeconomic status between cases and controls
|  | Cases n(%) | Controls n(%) | P-value (χ2 test) |
|---|---|---|---|
Age(years) | 325(100.0) | 325(100.0) | 0.545 |
   9-11 | 35(10.7) | 38(11.7) |  |
   12 | 54(16.6) | 58(17.8) |  |
   13 | 48(14.8) | 32(9.8) |  |
   14 | 83(25.5) | 97(29.8) |  |
   15 | 75(23.1) | 71(21.8) |  |
   16-18 | 30(9.2) | 29(8.9) |  |
Father's education | 325(100.0) | 325(100.0) | 0.605 |
   Illiteracy | 4(1.2) | 4(1.2) |  |
   Elementary school | 39(12.0) | 51(15.7) |  |
   High school | 140(43.1) | 148(45.5) |  |
   Undergraduate | 54(16.6) | 51(15.7) |  |
   Postgraduate and over | 21(6.5) | 14(4.3) |  |
   Unknown | 67(20.6) | 57(17.5) |  |
Mother's education | 252(100.0) | 255(100.0) | 0.558 |
   Illiteracy | 9(2.8) | 6(1.9) |  |
   Elementary school | 88(27.1) | 92(28.4) |  |
   High school | 101(31.1) | 109(33.6) |  |
   Undergraduate | 39(12.0) | 40(12.4) |  |
   Postgraduate and over | 15(4.6) | 8(2.5) |  |
   Unknown | 73(22.5) | 69(21.3) |  |
Household income | 325(100.0) | 325(100.0) | 0.344 |
   Low | 33(10.2) | 23(7.1) |  |
   In-betweens | 228(70.2) | 223(68.8) |  |
   High | 52(16.0) | 65(20.1) |  |
   Unknown | 12(3.7) | 13(4.0) |  |