Table 4. Hazard rates and 95% confidence intervals for possible risk factors associated with first episode of pneumonia during infancy by age group.
| Pneumonia episode at 0–5 months | Pneumonia episode at 6–11 months | Pneumonia episode during infancy | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Cases | CYO | Hazard Rate (95% CI) | Cases | CYO | Hazard rate (95% CI) | Cases | CYO | Hazard rate (95% CI) | ||
| Sex | ||||||||||
| Female | 9 | 98 | 0.09 (0.05–0.18) | 22 | 93 | 0.24 (0.15–0.36) | 31 | 190 | 0.16 (0.11–0.23) | |
| Male | 23 | 96 | 0.24 (0.16–0.36) | 35 | 82 | 0.43 (0.31–0.59) | 58 | 178 | 0.33 (0.25–0.42) | |
| Prematurity | ||||||||||
| At term | 30 | 188 | 0.16 (0.11–0.23) | 54 | 169 | 0.32 (0.25–0.42) | 84 | 356 | 0.24 (0.19–0.29) | |
| Less than 37 weeks | 0 | 0 | 0 | 3 | 4 | 0.74 (0.24–2.30) | 3 | 8 | 0.37 (0.12–1.16) | |
| Low birth weight | ||||||||||
| Normal | 30 | 182 | 0.17 (0.12–0.24) | 56 | 163 | 0.34 (0.27–0.45) | 86 | 345 | 0.24 (0.20–0.30) | |
| Low | 0 | 8·5 | 0 | 1 | 9 | 0.11 (0.02–0.80) | 1 | 17 | 0.58 (0.01–0.41) | |
| EBF | ||||||||||
| Yes | 20 | 107 | 0.19 (0.12–0.29) | 27 | 99 | 0.27 (0.19–0.40) | 47 | 207 | 0.23 (0.17–0.30) | |
| No | 12 | 84 | 0.14 (0.08–0.25) | 30 | 75 | 0.40 (0.28–0.57) | 42 | 160 | 0.26 (0.19–0.36) | |
| Number of people living in the house | ||||||||||
| < 7 people | 24 | 171 | 0.14 (0.09–0.21) | 50 | 156 | 0.32 (0.24–0.42) | 74 | 327 | 0.23 (0.18–0.28) | |
| ≥ 7 people | 8 | 23 | 0.35 (0.17–0.69) | 7 | 19 | 0.38 (0.18–0.79) | 15 | 42 | 0.36 (0.22–0.60) | |
| Mother sun exposure for the entire pregnancy | ||||||||||
| Weekday | ||||||||||
| (per 100 mW/m2/nm/hour). Interquartile range | ||||||||||
| Quartile 1 (91–174) | 9 | 46 | 0.20 (0.10–0.38) | 19 | 39 | 0.49 (0.31–0.76) | 28 | 85 | 0.33 (0.23–0.48) | |
| Quartile 2 (183–342) | 6 | 47 | 0.13 (0.06–0.29) | 16 | 43 | 0.37 (0.23–0.61) | 22 | 90 | 0.25 (0.16–0.37) | |
| Quartile 3 (363–379) | 10 | 42 | 0.24 (0.13–0.44) | 12 | 36 | 0.33 (0.19–0.58) | 22 | 78 | 0.28 (0.19–0.43) | |
| Quartile 4 (743–1134) | 5 | 45 | 0.11 (0.05–0.27) | 9 | 43 | 0.21 (0.11–0.41) | 14 | 88 | 0.16 (0.09–0.27) | |
| Weekend | ||||||||||
| (per 100 mW/m2/nm/hour). Interquartile range | ||||||||||
| Quartile 1 (91–174) | 9 | 50 | 0.18 (0.09–0.35) | 20 | 43 | 0.47 (0.30–0.72) | 29 | 92 | 0.31 (0.22–0.45) | |
| Quartile 2 (183–192) | 6 | 44 | 0.14 (0.06–0.30) | 13 | 41 | 0.31 (0.18–0.54) | 19 | 86 | 0.22 (0.14–0.35) | |
| Quartile 3 (356–378) | 9 | 47 | 0.19 (0.10–0.37) | 16 | 41 | 0.39 (0.24–0.64) | 25 | 88 | 0.29 (0.19–0.42) | |
| Quartile 4 (726–1134) | 6 | 49 | 0.12 (0.05–0.27) | 8 | 46 | 0.17 (0.09–0.35) | 14 | 96 | 0.15 (0.09–0.25) | |
| Infant cumulative sun exposure during 0–5 months of agea | ||||||||||
| Weekday | ||||||||||
| (per 100 mW/m2/nm/hour). Interquartile range | ||||||||||
| Quartile 1 (196–256) | NA | 14 | 44 | 0.32 (0.19–0.53) | NA | |||||
| Quartile 2 (303–350) | 16 | 42 | 0.38 (0.23–0.63) | |||||||
| Quartile 3 (394–459) | 13 | 43 | 0.30 (0.18–0.52) | |||||||
| Quartile 4 (559–806) | 12 | 41 | 0.29 (0.17–0.51) | |||||||
| Weekend | ||||||||||
| (per 100 mW/m2/nm/hour). Interquartile range | ||||||||||
| Quartile 1 (200–260) | NA | 16 | 40 | 0.40 (0.25–0.66) | NA | |||||
| Quartile 2 (303–351) | 12 | 40 | 0.30 (0.17–0.54) | |||||||
| Quartile 3 (396–465) | 13 | 39 | 0.33 (0.19–0.57) | |||||||
| Quartile 4 (567–835) | 11 | 38 | 0.29 (0.16–0.52) | |||||||
| Father smokes everyday | ||||||||||
| No | 12 | 94 | 0.13 (0.07–0.22) | 22 | 88 | 0.25 (0.17–0.38) | 34 | 182 | 0.19 (0.13–0.26) | |
| Yes | 20 | 99 | 0.20 (0.13–0.31) | 34 | 87 | 0.39 (0.28–0.55) | 54 | 186 | 0.29 (0.22–0.37) | |
| BCG vaccination | ||||||||||
| Yes | 31 | 184 | 0.17 (0.12–0.24) | 55 | 167 | 0.33 (0.25–0.43) | 86 | 351 | 0.25 (0.20–0.30) | |
| No | 1 | 10 | 0.10 (0.01–0.71) | 2 | 8 | 0.25 (0.06–1.00) | 3 | 18 | 0.17 (0.05–0.53) | |
| Cord blood vitamin D status | ||||||||||
| ≥ 50 nmol/L | 4 | 26 | 0.25 (0.09–0.66) | 5 | 14 | 0.36 (0.15–0.86) | 9 | 30 | 0.30 (0.16–0.57) | |
| < 50 nmol/L | 25 | 140 | 0.18 (0.12–0.26) | 42 | 126 | 0.33 (0.25–0.45) | 67 | 266 | 0.25 (0.20–0.32) | |
| Vitamin D status at 6 months | ||||||||||
| ≥ 50 nmol/L | NA | 32 | 91 | 0.35 (0.25–0.50) | NA | |||||
| < 50 nmol/L | 7 | 14 | 0.51 (0.24–1.07) | |||||||
Cases = number of infants had first episode of pneumonia.
CYO = child year of observation.
EBF = Exclusive breastfeeding.
Low birth weight (below 2500 grams) versus normal birth weight (2500–4000 grams).
Maternal sun exposure during pregnancy was defined as cumulative composite estimate UVR exposure during pregnancy which was product of time spent outdoors multiplied by the ambient ultraviolet B during the period of time (per 100 mW/m2/nm/hour).
Maternal cumulative composite weekday: quartile 1 (91–174 per 100 mW/m2/nm/hour); quartile 2 (183–342 per 100 mW/m2/nm/hour); quartile 3 (363–379 per 100 mW/m2/nm/hour); and quartile 4 (743–1134 per 100 mW/m2/nm/hour).
Maternal cumulative composite weekend: quartile 1 (91–174 per 100 mW/m2/nm/hour); quartile 2 (183–192 per 100 mW/m2/nm/hour); quartile 3 (356–378 per 100 mW/m2/nm/hour); and quartile 4 (726–1134 per 100 mW/m2/nm/hour).
Infant cumulative composite weekday: quartile 1 (196–256 per 100 mW/m2/nm/hour); quartile 2 (303–350 per 100 mW/m2/nm/hour); quartile 3 (394–459 per 100 mW/m2/nm/hour); and quartile 4 (559–806 per 100 mW/m2/nm/hour).
Infant cumulative composite weekend: quartile 1 (200–260 per 100 mW/m2/nm/hour); quartile 2 (303–351 per 100 mW/m2/nm/hour); quartile 3 (396–465 per 100 mW/m2/nm/hour); and quartile 4 (567–835 per 100 mW/m2/nm/hour).
NA = not applicable.
a The association between infant cumulative sun exposure and first episode of pneumonia was calculated on the basis of the temporal sequence of exposure before outcome which was not applicable to the association between infant cumulative sun exposure between 0–6 months of age and first episode of pneumonia between 0–6 months of age.