Factors that showed no interaction with the time periods studied
| Factor | SIDS n = 174 No (%) | Control n = 375 No (%) | Univariate OR (95% CI) | Multivariate OR (95% CI) | p value for interaction with period | ||
|---|---|---|---|---|---|---|---|
| Pregnancy2-150 | Complication | 75 (44) | 124 (33) | 1.52 (1.04 to 2.23) | 1.27 (0.78 to 2.07) | 0.35 | |
| Disease | 37 (22) | 36 (10) | 2.90 (1.71 to 4.91) | 2.85 (1.53 to 5.33) | 0.50 | ||
| Father smoking | 76 (46) | 150 (40) | 1.25 (0.85 to 1.82) | 1.00 (0.60 to 1.66) | 0.21 | ||
| Birth2-150 | Birth weight | ||||||
| <2.5 kg | 10 (6) | 17 (5) | 1.62 (0.67 to 3.92) | 1.81 (0.87 to 3.76) | 0.83 | ||
| 2.5–3.0 kg | 30 (18) | 18 (12) | 1.81 (0.98 to 3.36) | 1.24 (0.71 to 2.20) | |||
| 3.1–3.5 kg | 31 (31) | 132 (37) | 1.0 (ref) | 1.0 (ref) | |||
| 3.6–4.0 kg | 32 (32) | 106 (29) | 1.27 (0.79 to 2.06) | 1.01 (0.50 to 2.03) | |||
| >4.0 kg | 22 (13) | 61 (17) | 1.02 (0.56 to 1.86) | 0.65 (0.30 to 1.43) | |||
| Gestational age | |||||||
| <33 weeks | 8 (5) | 2 (1) | 9.70 (2.02 to 46.52) | 13.56 (1.25 to 147.4) | 0.83 | ||
| 33–34 weeks | 9 (1) | 3 (2) | 0.57 (0.11 to 2.83) | 1.10 (0.13 to 9.18) | |||
| 35–36 weeks | 10 (3) | 10 (3) | 1.54 (0.55 to 3.33) | 0.59 (0.16 to 2.12) | |||
| 37–38 weeks | 11 (11) | 45 (11) | 1.03 (0.57 to 1.85) | 0.65 (0.30 to 1.43) | |||
| 39–40 weeks | 139 (80) | 311 (83) | 1.0 (ref) | 1.0 (ref) | |||
| Birth order | |||||||
| Firstborn | 47 (27) | 147 (42) | 1.0 (ref) | 1.0 (ref) | 0.49 | ||
| No. 2 | 48 (38) | 137 (39) | 1.66 (1.04 to 2.65) | 2.42 (1.37 to 4.26) | |||
| No. 3 | 49 (22) | 52 (15) | 2.22 (1.28 to 3.84) | 3.56 (1.71 to 7.42) | |||
| No. 4 or later | 23 (13) | 15 (4) | 4.32 (2.09 to 8.92) | 8.30 (3.16 to 21.84) | |||
| Usual mode of sleep and feeding habit2-151 | Sleeping position | ||||||
| Prone | 109 (64) | 147 (39) | 2.71 (1.21 to 6.07) | 1.39 (0.61 to 3.20) | 0.66 | ||
| Side | 24 (14) | 123 (33) | 0.40 (0.19 to 0.86) | 0.30 (0.12 to 0.77) | |||
| Side/back | 17 (10) | 65 (17) | 0.53 (0.24 to 1.19) | 0.38 (0.14 to 1.12) | |||
| Back | 21 (12) | 38 (10) | 1.0 (ref) | 1.0 (ref) | |||
| Waking at night2-152 | |||||||
| Always | 5 (3) | 36 (10) | 1.0 (ref) | 1.0 (ref) | 0.10 | ||
| Often | 6 (4) | 37(21) | 0.48 (0.13 to 1.79) | 0.35 (0.08 to 1.45) | |||
| Sometimes | 7 (12) | 104 (29) | 1.36 (0.46 to 4.04) | 1.03 (0.31 to 3.46) | |||
| Seldom | 8 (49) | 105 (29) | 6.68 (2.05 to 15.67) | 5.27 (1.71 to 16.27) | |||
| Never | 53 (32) | 40 (11) | 9.80 (3.33 to 28.90) | 9.29 (2.79 to 30.85) | |||
| Co-sleeping | 15 (9) | 24 (6) | 1.37 (0.68 to 2.77) | 1.66 (0.57 to 4.85) | 0.60 | ||
| Breast feeding > 3 months2-152 | 124 (71) | 275 (75) | 0.81 (0.54 to 1.21) | 1.69 (0.90 to 3.19) | 0.56 | ||
| Dummy use2-151 | 0–4 months daytime | ||||||
| Ever | 73 (55) | 218 (68) | 0.56 (0.37 to 0.85) | 0.51 (0.27 to 0.96) | 0.68 | ||
| Never | 61 (45) | 102 (32) | 1.0 (ref) | 1.0 (ref) | |||
| 0–4 months night-time | |||||||
| Ever | 59 (47) | 203 (63) | 0.51 (0.33 to 0.77) | 0.36 (0.18 to 0.69) | 0.83 | ||
| Never | 67 (53) | 117 (37) | 1.0 (ref) | 1.0 (ref) | |||
| Sosioeconomic factors2-151 | Social class mother2-153 | ||||||
| I | 23 (13) | 32 (9) | 1.0 (ref) | 1.0 (ref) | 0.76 | ||
| II | 17 (10) | 56 (15) | 0.42 (0.19 to 0.90) | 0.61 (0.22 to 1.71) | |||
| III | 95 (55) | 208 (56) | 0.63 (0.35 to 1.14) | 0.57 (0.25 to 1.30) | |||
| IV | 4 (2) | 7 (2) | 0.79 (0.20 to 3.04) | 0.25 (0.04 to 1.53) | |||
| V | 34 (20) | 68 (18) | 0.69 (0.35 to 1.37) | 1.29 (0.51 to 3.27) | |||
| Social class father2-153 | |||||||
| I | 31 (19) | 42 (12) | 1.0 (ref) | 1.0 (ref) | 0.19 | ||
| II | 30 (18) | 79 (22) | 0.51 (0.27 to 0.96) | 0.52 (0.22 to 1.23) | |||
| III | 52 (31) | 132 (36) | 0.53 (0.30 to 0.93) | 0.78 (0.35 to 1.74) | |||
| IV | 36 (22) | 67 (18) | 0.72 (0.39 to 1.34) | 1.27 (0.51 to 3.21) | |||
| V | 17 (10) | 44 (10) | 0.52 (0.25 to 1.08) | 0.58 (0.20 to 1.72) | |||
↵2-150 The multivariate model controls for the following variables: disease and complications in pregnancy, birth weight, gestational age, birth order, mother's age at time of pregnancy, mother's and father's smoking habits during pregnancy, and social class/occupational status at the time of pregnancy.
↵2-151 The multivariate model controls for the following variables: birth weight, gestational age, birth order, breast feeding over three months, waking at night, co-sleeping, sleeping position, dummy use, mother's and father's smoking habit during pregnancy, and social class/occupational status at the time of pregnancy.
↵2-152 For SIDS cases breast feeding until time of death or over 3 months.
↵2-153 Based on occupation at time of pregnancy studied according to the British registrar general's classification (I = professional, II = executive, III = skilled, IV = semi-skilled, V = unskilled). Housewives and students are classified under III.