Table 2. Distribution (frequencies) and association of potential risk factors with infant mortality in the 1992–3 and 2002–3 birth cohorts (univariate and multivariate analyses).
| Risk factor | 1992–3 cohort | 2002–3 cohort | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| N | % | Mortality Rate pr. 1000 PYRSa | Hazard ratio (95%CI)* | Adjusted Hazard ratio (95%CI)* | N | % | Mortality Rate pr. 1000 PYRSa | Hazard ratio (95%CI)* | Adjusted Hazard ratio (95%CI)* | Interaction with cohort (p-value) Univariate/ Multivariate |
|
| Sex of childb | [p = 0.11] | [p = 0.44] | [p<0.01] | [p<0.01] | 0.11 / 0.08 | ||||||
| Boy | 1899 | 51% | 157 (139–177) | 1.00 (ref) | 1.00 (ref) | 2304 | 51% | 147 (130–165) | 1.00 (ref) | 1.00 (ref) | |
| Girl | 1803 | 49% | 136 (119–156) | 0.86 (0.72–1.04) | 0.92 (0.75–1.13) | 2221 | 49% | 101 (88–116) | 0.69 (0.58–0.83) | 0.72 (0.59–0.87) | |
| Region of birth | [p = 0.08] | [p = 0.73] | [p = 0.58] | [p = 0.73] | 0.46 / 0.67 | ||||||
| Oio | 802 | 22% | 167 (139–201) | 1.00 (ref) | 1.00 (ref) | 945 | 21% | 115 (93–141) | 1.00 (ref) | 1.00 (ref) | |
| Biombo | 929 | 25% | 157 (132–187) | 0.94 (0.73–1.22) | 0.83 (0.59–1.17) | 1055 | 23% | 133 (111–159) | 1.19 (0.91–1.57) | 1.07 (0.79–1.47) | |
| Gabu | 761 | 21% | 134 (109–165) | 0.81 (0.61–1.06) | 0.87 (0.60–1.27) | 934 | 21% | 114 (93–139) | 0.98 (0.74–1.31) | 1.00 (0.73–1.36) | |
| Cacheu | 534 | 14% | 132 (113–174) | 0.81 (0.59–1.11) | 0.80 (0.56–1.14) | 799 | 18% | 125 (100–156) | 1.12 (0.83–1.52) | 1.04 (0.75–1.45) | |
| Bafata | 680 | 18% | 140 (113–174) | 0.83 (0.63–1.11) | 0.80 (0.56–1.14) | 793 | 18% | 137 (111–168) | 1.19 (0.89–1.59) | 1.22 (0.89–1.67) | |
| Season of birth | [p = 0.42] | [p = 0.21] | [p = 0.72] | [p = 0.60] | 0.41/ 0.22 | ||||||
| Rainy season | 1665 | 45% | 153 (134–175) | 1.00 (ref) | 1.00 (ref) | 1965 | 43% | 123 (107–142) | 1.00 (ref) | 1.00 (ref) | |
| Dry season | 2041 | 55% | 144 (127–162) | 0.93 (0.78–1.11) | 0.90 (0.75–1.07) | 2561 | 57% | 125 (111–141) | 1.03 (0.86–1.24) | 1.05 (0.87–1.28) | |
| Maternal age at child birth | [p = 0.24] | [p = 0.81] | 0.26/ NA | ||||||||
| <20 years | 805 | 22% | 185 (155–221) | 1.00 (ref) | 988 | 22% | 150 (125–181) | 1.00 (ref) | |||
| 20–24 years | 942 | 25% | 120 (99–146) | 0.65 (0.50–0.85) | 1347 | 30% | 108 (91–129) | 0.71 (0.55–0.91) | |||
| 25–29 years | 933 | 25% | 153 (128–182) | 0.83 (0.64–1.06) | 1021 | 23% | 101 (82–125) | 0.65 (0.49–0.86) | |||
| 30–34 years | 614 | 17% | 139 (111–174) | 0.76 (0.57–1.01) | 662 | 15% | 146 (118–182) | 0.93 (0.70–1.23) | |||
| 35+ years | 412 | 11% | 143 (109–189) | 0.78 (0.56–1.09) | 508 | 11% | 138 (107–177) | 0.88 (0.65–1.20) | |||
| Ethnicity of motherd | [p = 0.20] | [p = 0.08] | 0.07/ NA | ||||||||
| Fula | 975 | 26% | 150 (126–179) | 1.00 (ref) | 849 | 19% | 111 (92–133) | 1.00 (ref) | |||
| Balanta | 681 | 18% | 183 (151–221) | 1.21 (0.93–1.57) | 1181 | 26% | 107 (85–134) | 0.99 (0.74–1.32) | |||
| Mandinga | 744 | 20% | 125 (100–155) | 0.83 (0.63–1.10) | 974 | 22% | 151 (127–180) | 1.38 (1.07–1.78) | |||
| Manjaco | 236 | 6% | 106 (70–161) | 0.72 (0.46–1.14) | 350 | 8% | 99 (68–143) | 0.94 (0.62–1.42) | |||
| Pepel | 789 | 21% | 153 (126–185) | 1.02 (0.79–1.32) | 871 | 19% | 142 (117–172) | 1.33 (1.02–1.74) | |||
| Other | 281 | 8% | 141 (100–198) | 0.95 (0.65–1.39) | 292 | 6% | 118 (81–171) | 1.09 (0.72–1.64) | |||
| Maternal schoolinge | [p = 0.74] | [p = 0.84] | [p = 0.79] | [p = 0.85] | 0.70/0.97 | ||||||
| Never went to school | 3198 | 87% | 148 (135–164) | 1.00 (ref) | 1.00 (ref) | 3793 | 85% | 126 (114–139) | 1.00 (ref) | 1.00 (ref) | |
| Went to school | 466 | 13% | 141 (109–183) | 0.95 (0.72–1.26) | 1.04 (0.73–1.47) | 691 | 15% | 118 (93–151) | 0.96 (0.74–1.25) | 0.97 (0.74–1.28) | |
| Health facility within the village? | [p = 0.01] | [p = 0.04] | [p = 0.51] | [p = 0.98] | 0.16/0.22 | ||||||
| Yes | 1893 | 51% | 130 (113–148) | 1.00 (ref) | 1.00 (ref) | 2251 | 50% | 121 (106–137) | 1.00 (ref) | 1.00 (ref) | |
| No | 1813 | 49% | 167 (148–189) | 1.28 (1.07–1.53) | 1.29 (1.01–1.66) | 2275 | 50% | 128 (113–145) | 1.06 (0.89–1.27) | 1.00 (0.81–1.23) | |
| Distance to nearest health facility (any kind) | [p = 0.04] | [p = 0.88] | 0.51/NA | ||||||||
| <1 km | 1893 | 51% | 130 (113–148) | 1.00 (ref) | 2275 | 50% | 121 (106–137) | 1.00 (ref) | |||
| 1–4 km | 835 | 23% | 176 (147–210) | 1.35 (1.08–1.68) | 979 | 22% | 135 (112–163) | 1.13 (0.90–1.41) | |||
| 5–9 km | 662 | 18% | 152 (124–188) | 1.17 (0.91–1.50) | 827 | 18% | 123 (100–152) | 1.03 (0.80–1.31) | |||
| 10+ km | 316 | 9% | 175 (131–233) | 1.33 (0.97–1.83) | 445 | 10% | 121 (90–162) | 1.00 (0.72–1.37) | |||
| Distance to nearest hospital | [p = 0.23] | [p = 0.50] | [p = 0.01] | [p = 0.03] | 0.64/0.55 | ||||||
| <10 km | 614 | 17% | 141 (112–177) | 1.00 (ref) | 1.00 (ref) | 686 | 15% | 96 (74–126) | 1.00 (ref) | 1.00 (ref) | |
| 10–20 km | 666 | 18% | 142 (114–176) | 1.01 (0.74–1.38) | 0.96 (0.69–1.32) | 967 | 21% | 120 (98–146) | 1.23 (0.89–1.71) | 1.36 (0.96–1.92) | |
| 21–29 km | 685 | 18% | 129 (104–162) | 0.92 (0.67–1.26) | 0.85 (0.59–1.23) | 813 | 18% | 108 (86–136) | 1.11 (0.78–1.57) | 1.15 (0.79–1.68) | |
| 30+ km | 1741 | 47% | 160 (141–182) | 1.14 (0.88–1.48) | 1.13 (0.87–1.46) | 2060 | 46% | 142 (126–162) | 1.48 (1.11–1.98) | 1.54 (1.13–2.11) | |
| Place of giving birthc,f | [p = 0.78] | [0.13] | 0.23/NA | ||||||||
| At hospital/health centre | 823 | 27% | 143 (120–171) | 1.00 (ref) | 800 | 26% | 149 (123–180) | 1.00 (ref) | |||
| At home | 2198 | 73% | 146 (131–162) | 0.97 (0.78–1.21) | 2308 | 74% | 125 (111–141) | 0.84 (0.67–1.05) | |||
| Born with skilled attendance?c,g | [p = 0.35] | [p = 0.10] | 0.08/NA | ||||||||
| Yes | 1085 | 37% | 136 (115–162) | 1.00 (ref) | 1152 | 38% | 145 (123–170) | 1.00 (ref) | |||
| No | 1814 | 63% | 151 (133–171) | 1.11 (0.90–1.36) | 1852 | 62% | 119 (104–137) | 0.83 (0.66–1.03) | |||
| Was the child a twin?h | [p<0.01] | [p<0.01] | [p<0.01] | [p<0.01] | 0.46/0.41 | ||||||
| No | 3602 | 97% | 143 (131–157) | 1.00 (ref) | 1.00 (ref) | 4367 | 96% | 118 (107–129) | 1.00 (ref) | 1.00 (ref) | |
| Yes | 102 | 3% | 333 (227–489) | 2.23 (1.50–3.30) | 2.51 (1.58–3.98) | 159 | 4% | 334 (244–457) | 2.70 (1.94–3.75) | 2.96 (2.09–4.21) | |
| Number of older siblings for the childi | [p = 0.01] | [p<0.01] | [p = 0.39] | [p<0.01] | 0.06/0.08 | ||||||
| 0 | 506 | 15% | 224 (182–274) | 1.00 (ref) | 1.00 (ref) | 671 | 17% | 159 (129–196) | 1.00 (ref) | 1.00 (ref) | |
| 1–2 | 1118 | 34% | 133 (112–158) | 0.60 (0.46–0.78) | 0.52 (0.39–0.71) | 1423 | 36% | 123 (104–145) | 0.81 (0.62–1.06) | 0.69 (0.52–0.91) | |
| 3–4 | 486 | 15% | 151 (118–193) | 0.67 (0.49–0.93) | 0.57 (0.39–0.82) | 590 | 15% | 91 (68–122) | 0.59 (0.41–0.84) | 0.47 (0.32–0.69) | |
| ≥5 | 1157 | 35% | 135 (114–160) | 0.61 (0.47–0.80) | 0.46 (0.31–0.68) | 1289 | 32% | 137 (117–160) | 0.87 (0.67–1.13) | 0.58 (0.42–0.80) | |
| Previously lost a child | [p = 0.52] | [p = 0.05] | [p<0.01] | [p<0.01] | 0.10/0.12 | ||||||
| No | 1754 | 47% | 142 (125–163) | 1.00 (ref) | 1.00 (ref) | 2550 | 56% | 108 (95–123) | 1.00 (ref) | 1.00 (ref) | |
| Yes | 1952 | 53% | 153 (135–172) | 1.06 (0.88–1.27) | 1.33 (1.01–1.77) | 1976 | 44% | 145 (128–164) | 1.31 (1.10–1.58) | 1.56 (1.23–2.00) | |
*Estimated in a Cox proportional hazards model with age as underlying timescale; 95%CI adjusted for cluster sampling using robust variance estimates
a: PYRS: Person-years
b: Sex missing for 4 children in 1992–3 and for 1 child in 2002–3
c: Only for children registered before birth
d: Ethnicity missing for 9 mothers in 2002–3
e: Education missing for 42 mothers in both 1992–3 and in 2002–3
f: Place of giving birth missing for 83 infants in 1992–3 and for 33 in 2002–3
g: Skilled attendance at birth missing for 205 infants in 1992–3 and for 137 in 2002–3
h: Twin status missing for 2 infants in 1992–3
i: Number of older siblings missing for 439 infants in 1992–3 and for 553 in 2002–3