TABLE 1.
HRs of PS According to Feeding Practice Characteristics
| Feeding Practice Characteristics | Number of PS Cases | HR (95% CI)a | P |
|---|---|---|---|
| Exposure to bottle-feeding | |||
| Not bottle-fed | 36 | 1 (reference) | <.0001 |
| Bottle-fed | 29 | 4.62b (2.78–7.65) | — |
| Combination of breast and bottle-feeding | |||
| Not bottle-fed | 36 | 1 (reference) | — |
| Bottle-fedc | |||
| Both breast and bottle-fed | 9 | 3.36d (1.60–7.03) | |
| Formerly breastfed | 15 | 5.38 (2.88–10.06) | .76 |
| Never breastfed | 5 | 6.32d (2.45–16.26) | |
| Time since first exposure to bottle-feedinge | |||
| Not bottle-fed | 36 | 1 (reference) | — |
| Bottle-fed | |||
| <30 d | 18 | 4.50 (2.53–8.01) | .98 |
| ≥30 d | 11 | 4.85 (2.33–10.07) | |
| Age at first exposure to bottle-feeding | |||
| Not bottle-fed | 36 | 1 (reference) | — |
| Bottle-fed | |||
| <30 d | 25 | 5.00 (2.97–8.41) | .26 |
| ≥30 d | 4 | 2.95 (0.99–8.72) |
HR adjusted for age, gender, gestational age, birth weight, birth order, maternal age, and maternal smoking during pregnancy. Adjusting only for age increases HR to 5.05 (3.07–8.30), primarily due to not adjusting for maternal smoking during pregnancy.
Additionally adjusting for mothers’ socioeconomic status (occupation and school skills), type of birth (vaginal/caesarean section) and maternal smoking during breastfeeding, and postnatal yield similar results.
Among the bottle-fed infants, the median age at diagnosis was 40 d for both breast and bottle-feeding infants, and 35 d for formerly breastfed infants now receiving only bottle-feeding. Five infants with PS were never breast-fed, and among them, the age at diagnosis ranged from 13 to 35 d, with a median age of 26 d. Furthermore, among the infants who were bottle-fed, the time of follow-up was 2027 person-years for those both breast and bottle-fed, 2332 person-years for those formerly breastfed, and 422 person-years for those never breastfed (exclusively bottle-fed).
The ratio between the HR for both breast and bottle-fed infants and the HR for never breastfed was 1.88 (0.63–5.66).
Among the bottle-fed infants, the HR of PS was 4.91 (95% CI: 2.34–10.31) <14 d since first exposure to bottle-feeding and 4.48 (95% CI: 2.53–7.94) >14 d since first exposure to bottle-feeding. Less than 14 d since first exposure to bottle-feeding, there were 9 cases: 3 cases within the first 48 h and 6 cases in the second week.