|  | CIRR (95% CI) | p-value | AIRR (95% CI) | p-value |
---|---|---|---|---|---|
Age of the mother (years) | ≥ 32 vs. <32 | 1.13 (0.80 -1.58) | 0.49 | 1.08 (0.75 -1.55) | 0.67 |
Parity | 1 vs. 0 | 1.28 (0.88 -1.86) | 0.19 | 1.34 (0.91 -1.98) | 0.14 |
 | ≥ 2 vs. 0 | 1.04 (0.59 -1.83) | 0.89 | 1.09 (0.60 -1.95) | 0.78 |
Years of education | ≤ 8 vs. >8 | 1.74 (1.23 -2.46) | <0.01 | 1.71 (1.18 -2.48) | 0.01 |
 | Not known vs. >8 | 9.51 (0.88 -102.1) | 0.06 | 9.82 (0.79 -122.4) | 0.08 |
Birth country of the mother | Italy vs. other | 1.07 (0.65 -1.78) | 0.78 | 1.30 (0.73 -2.30) | 0.37 |
Gender | male vs female | 1.47 (1.03 -2.08) | 0.03 | 1.48 (1.04 -2.10) | 0.03 |
Calendar year (ref. 2001) | 2000 | 1.19 (0.49 -2.86) | 0.70 | 0.79 (0.33 -1.88) | 0.60 |
 | 2002 | 1.21 (0.64 -2.28) | 0.56 | 1.28 (0.68 -2.43) | 0.44 |
 | 2003 | 1.61 (0.89 -2.93) | 0.12 | 1.73 (0.95 -3.16) | 0.07 |
 | 2004 | 0.84 (0.43 -1.63) | 0.61 | 0.92 (0.47 -1.79) | 0.81 |
 | 2005 | 1.02 (0.54 -1.92) | 0.94 | 1.24 (0.66 -2.34) | 0.50 |
 | 2006 | 0.98 (0.51 -1.87) | 0.94 | 1.16 (0.60 -2.24) | 0.66 |
Age (months) | <6 vs. ≥ 12 | 11.75 (5.44 -25.35) | <0.01 | 14.54 (6.75 -31.35) | <0.01 |
 | 6-11 vs. ≥ 12 | 5.50 (2.47 -12.24) | <0.01 | 5.98 (2.68 -13.35) | <0.01 |
Epidemic period | Yes vs. No | 5.89 (3.44 -10.06) | <0.01 | 5.48 (3.22 -9.35) | <0.01 |
Birth weight | per 100 g decrease | 1.05 (1.02 -1.07) | <0.01 | 1.06 (1.02 -1.11) | 0.01 |
Gestational age | per 1 week less | 1.08 (1.02 -1.14) | 0.01 | 0.97 (0.88 -1.07) | 0.58 |
Apgar score | ≤ 7 vs. > 7 | 2.06 (1.40 -3.03) | <0.01 | 1.57 (0.99 -2.48) | 0.05 |
Broncho-dysplasia | Yes vs. No | 2.08 (0.91 -4.75) | 0.08 | 1.70 (0.68 -4.28) | 0.26 |
Congenital heart disease | Yes vs. No | 1.63 (0.51 -5.18) | 0.41 | 1.64 (0.52 -5.19) | 0.40 |