TABLE 2

SIDS Risk Factors by Time Perioda

Pre-BTS 1991–1993Transition Period 1994–1995BTS Era 1996–2008P value Pre Versus Postb
No. of SIDS cases16992307
Age, dc100.2 ± 55.3, (91), 10–322100.0 ± 56.6, (87.5), 20–276101.3 ± 63.5, (86), 2–326.85
Aged.11
 <2 mo38 (22.5%)22 (23.9%)80 (26.1%)
 2–4 mo111 (65.7%)57 (62.0%)173 (56.4%)
 ≥5 mo20 (11.8%)13 (14.1%)54 (17.6%)
Gender.58
 Male98 (58.0%)61 (66.3%)186 (60.6%)
 Female71 (42.0%)31 (33.7%)121 (39.4%)
Race.14
 White83 (49.1%)42 (45.7%)135 (44.1%)
 African American28 (16.6%)16 (17.4%)39 (12.8%)
 Hispanic50 (29.6%)28 (30.4%)103 (33.7%)
 Other8 (4.7%)6 (6.5%)29 (9.5%)
Death in winter69 (40.8%)34 (37.0%)138 (45.0%).39
Prematuritye28 (20.0%)30 (36.6%)78 (29.0%).05
Twin or tripletf9 (5.7%)9 (10.2%)16 (5.4%).90
Ever breastfed52 (80.0%)28 (84.9%)155 (78.7%).82
Breastfed at time of death26 (16.7%)16 (18.4%)73 (25.2%).04
Maternal smoking37 (42.1%)27 (37.0%)78 (38.6%).58
Maternal alcohol use during pregnancy7 (7.7%)5 (6.8%)8 (6.7%).77
Maternal drug use during pregnancy18 (18.4%)11 (14.5%)15 (11.9%).18
Symptoms of URTI75 (46.6%)38 (44.2%)72 (24.8%)<.001
Sleep siteg<.001
 Crib, bassinet, toddler bed, stroller lying flat100 (59.9%)41 (46.6%)112 (36.6%)
 Adult bed39 (23.4%)37 (42.1%)139 (45.4%)
 Couch, recliner, other soft chairh12 (7.2%)4 (4.6%)18 (5.9%)
 Waterbed or inflatable bed3 (1.8%)1 (1.1%)0 (0.0%)
 Car seat, car bed, bouncy chair3 (1.8%)0 (0.0%)14 (4.6%)
 Floor, possibly on pillow or blanket4 (2.4%)2 (2.3%)11 (3.6%)
 Playpen3 (1.8%)2 (2.3%)10 (3.3%)
 Being held, breastfeeding, in a sling3 (1.8%)1 (1.1%)1 (0.3%)
 Other0 (0.0%)0 (0.0%)1 (0.3%)
 Unknowni241
Sleep position placedj<.001
 Prone88 (85.4%)32 (53.3%)80 (30.1%)
 Side10 (9.7%)15 (25.0%)60 (22.6%)
 Supine2 (1.9%)12 (20.0%)111 (41.7%)
 Car seat/bouncy seat2 (1.9%)0 (0.0%)14 (5.3%)
 Being held1 (1.9%)1 (1.7%)1 (0.4%)
 Unknowni663241
Sleep position foundj<.001
 Prone110 (84.0%)49 (57.7%)132 (48.5%)k
 Side9 (6.9%)18 (21.2%)47 (17.3%)
 Supine9 (6.9%)18 (21.2%)79 (29.0%)
 Car seat/bouncy seat2 (1.5%)0 (0.0%)14 (5.2%)
 Being held1 (0.8%)0 (0.0%)0 (0.0%)
 Unknowni38735
Face position.001
 Down47 (45.2%)24 (34.3%)78 (33.8%)
 Side50 (48.1%)32 (45.7%)102 (44.2%)
 Up7 (6.7%)14 (20.0%)51 (22.1%)
 Unknowni652276
Face obstructed12 (7.6%)4 (4.6%)16 (5.7%).44
Bed-sharing32 (19.2%)21 (25.0%)114 (37.9%)l<.001
Bed-sharing with other children3 (1.8%)2 (2.4%)10 (3.4%).34
No. of known intrinsic risk factorsm1.3 ± 1.0, (1) 0–51.7 ± 1.2, (1) 0–51.4 ± 1.0, (1) 0–4.70
 ≥1 intrinsic risk factor134 (79.3%)81 (88.0%)260 (84.7%).14
 ≥2 intrinsic risk factors66 (39.1%)45 (48.9%)110 (35.8%).49
No. of known extrinsic risk factors2.1 ± 1.3, (2) 0–62.3 ± 1.2, (2) 0–52.1 ± 1.2, (2) 0–6.78
 ≥1 extrinsic risk factor155 (91.7%)85 (92.4%)274 (89.3%).39
 ≥2 extrinsic risk factors109 (64.5%)69 (75.0%)211 (68.7%).35
  • a Continuous variables are summarized as mean ± SD, (median), range; categorical variables are presented as n (%). Some risk factors contain considerable missing data (eg, maternal smoking, alcohol, and drug use).

  • b Only the comparison between pre-BTS and the BTS era was tested, because 1994–1995 was considered a time of continual change in population practice. t test was used for continuous variables; χ2 tests were used for categorical variables. The category “unknown” was always excluded from analysis.

  • c The interquartile range is 62–121 pre-BTS, 63.5–129.5 transition period, and 59–125 BTS era.

  • d Younger than 1 mo changed from 3.6% pre-BTS to 8.1% in the BTS era; 1 mo changed from 18.9% to 17.9%; 5 mo changed from 3.6% to 6.8%; 6+ months changed from 8.3% to 10.8%.

  • e Defined as <37 wk gestation.

  • f Thirty-three twins; 1 triplet post-BTS.

  • g Because of the inadequate sample size of most categories, the P value reflects a test of crib/bassinet/toddler bed/stroller lying flat versus adult bed. A toddler bed uses a crib mattress.

  • h Of these, almost all were sleeping on a couch: 8 pre-BTS, 4 transition period, and 17 BTS era. 47% of infants sleeping on a couch, recliner, or other soft chair were bed-sharing, remaining steady from 50% (n = 6) pre-BTS to 47% (n = 8) in the BTS era.

  • i The category “unknown” was excluded from statistical comparisons. It is presented only for completeness of data.

  • j Because of the inadequate sample size of some categories, the P value reflects a test of prone versus side versus supine.

  • k Fifty-nine percent prone from 1996 to 1999, 44% from 2000 to 2003, 30% from 2004 to 2008.

  • l Twenty-eight percent bed-sharing from 1996 to 1999, 44% from 2000 to 2003, 41% from 2004 to 2008.

  • m If male gender is excluded, female SIDS infants had an average of 0.75 to 1.07 other intrinsic risks across study periods.