ORIGINAL CONTRIBUTION
Risk Factors for Sudden Infant Death
Syndrome Among Northern Plains Indians
Solomon Iyasu, MBBS, MPH
Leslie L. Randall, RN, MPH
Thomas K. Welty, MD
Jason Hsia, PhD
Hannah C. Kinney, MD
Frederick Mandell, MD
Mary McClain, RN, MS
Brad Randall, MD
Don Habbe, MD
Harry Wilson, MD
Marian Willinger, PhD
T
HE INFANT MORTALITY RATE
among American Indians is consistently above the national average, primarily due to a higher
death rate during the postneonatal period (28-364 days). Sudden infant death
syndrome (SIDS) is the leading cause of
postneonatal mortality, and until 1997,
was also the leading cause of infant mortality among American Indians.1-3 SIDS
is defined as the sudden death of an infant younger than 1 year that remains unexplained after a thorough case investigation, including the performance of a
complete autopsy, an examination of the
death scene, and a review of the infant’s
clinical history.4 In 1999, the SIDS rate
was 1.5 per 1000 live births for American Indian infants and 0.7 per 1000 live
births for all races combined.5
The Aberdeen Area Indian Health Service (AAIHS), which serves Indian communities in North Dakota, South Dakota, Nebraska, and Iowa, has the highest
rate of infant mortality among the Indian Health Service (IHS) areas.6,7 SIDS
is the leading cause of infant deaths in
See also Patient Page.
Context Sudden infant death syndrome (SIDS) is a leading cause of postneonatal
mortality among American Indians, a group whose infant death rate is consistently
above the US national average.
Objective To determine prenatal and postnatal risk factors for SIDS among American Indians.
Design, Setting, and Participants Population-based case-control study of 33 SIDS
infants and 66 matched living controls among American Indians in South Dakota, North
Dakota, Nebraska, and Iowa enrolled from December 1992 to November 1996 and
investigated using standardized parental interview, medical record abstraction, autopsy protocol, and infant death review.
Main Outcome Measures Association of SIDS with maternal socioeconomic and
behavioral factors, health care utilization, and infant care practices.
Results The proportions of case and control infants who were usually placed prone
to sleep (15.2% and 13.6%, respectively), who shared a bed with parents (59.4%
and 55.4%), or whose mothers smoked during pregnancy (69.7% and 54.6%) were
similar. However, mothers of 72.7% of case infants and 45.5% of control infants engaged in binge drinking during pregnancy. Conditional logistic regression revealed significant associations between SIDS and 2 or more layers of clothing on the infant (adjusted odds ratio [aOR], 6.2; 95% confidence interval [CI], 1.4-26.5), any visits by a
public health nurse (aOR, 0.2; 95% CI, 0.1-0.8), periconceptional maternal alcohol
use (aOR, 6.2; 95% CI, 1.6-23.3), and maternal first-trimester binge drinking (aOR,
8.2; 95% CI, 1.9-35.3).
Conclusions Public health nurse visits, maternal alcohol use during the periconceptional period and first trimester, and layers of clothing are important risk factors for
SIDS among Northern Plains Indians. Strengthening public health nurse visiting programs and programs to reduce alcohol consumption among women of childbearing
age could potentially reduce the high rate of SIDS.
www.jama.com
JAMA. 2002;288:2717-2723
the Aberdeen Area, accounting for more
than one fourth of the infant deaths and
more than half of the postneonatal
deaths. Although there was a 42% decline in the SIDS rates for all IHS regions, from 2.77 per 1000 live births in
1992-19946 to 1.61 per 1000 in 19961998,7 the rate in the Aberdeen Area has
remained relatively constant: 3.66, 3.55,
and 3.46 per 1000 live births for 19921994, 1994-1996, and 1996-1998, respectively.6-8
Author Affiliations: Division of Reproductive Health,
National Center for Chronic Disease Prevention and
Health Promotion, Centers for Disease Control and Prevention, Atlanta, Ga (Drs Iyasu and Hsia and Ms Randall); Aberdeen Area Indian Health Service, Rapid City,
SD (Dr Welty); Children’s Hospital Boston, Harvard
Medical School, Boston, Mass (Dr Kinney); Harvard
Medical School, Boston, Mass (Dr Mandell); Massachusetts SIDS Center, Boston Medical Center, Boston (Ms McClain); LCM Pathologists, PC, Sioux Falls,
SD (Dr Randall); Clinical Laboratory of the Black Hills,
Rapid City, SD (Dr Habbe); Department of Pathology, Providence Memorial Hospital, El Paso, Tex
(Dr Wilson); and National Institute of Child Health and
Human Development, National Institutes of Health,
Bethesda, Md (Dr Willinger). Dr Iyasu is now with the
Division of Pediatrics, Office of Counter Terrorism and
Pediatric Drug Development, Center for Drug Evaluation and Research, Food and Drug Administration,
Rockville, Md.
Corresponding Author and Reprints: Solomon Iyasu,
MBBS, MPH, Division of Pediatrics, Office of Counter
Terrorism and Pediatric Drug Development, Center for
Drug Evaluation and Research, Food and Drug Administration, 5A-33, HFD-960, 5600 Fishers Ln, Rockville, MD 20857 (e-mail: [email protected]).
©2002 American Medical Association. All rights reserved.
(Reprinted) JAMA, December 4, 2002—Vol 288, No. 21
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2717
SIDS AMONG NORTHERN PLAINS INDIANS
One of the objectives of the Aberdeen Area Infant Mortality Study
(AAIMS), which was conducted in collaboration with the Aberdeen Area Tribal
Chairman’s Health Board, was to determine prenatal and postnatal risk and
protective factors for SIDS among Northern Plains American Indian infants.
METHODS
From December 1, 1992, through November 30, 1996, a case-control study
was conducted in the AAIHS. Nine tribes
and 1 urban American Indian community, constituting two thirds of the service area population, participated. The
methodology has been previously described9 and is summarized below.
Tribal resolutions of support for the
study were obtained. After investigators obtained input from tribal spiritual leaders, the AAIHS and the National IHS institutional review boards
approved the study protocol. Informed consent was obtained from a
parent or legal guardian to conduct the
parental interviews and review the
medical records.
Cases
Eligible cases were American Indian infants residing on or near reservations
or participating communities who died
before 1 year of age, excluding infants
who died during their delivery hospitalization. Case infants were classified
as American Indian if either of their parents was an enrolled tribal member or
if they were eligible for care at an IHS
facility. Reports from public health
nurses (PHNs), medical record department staff, emergency staff, members
of the Perinatal Infant Mortality Review (PIMR) Committee, death certificates on American Indian infants, and
obituaries in local newspapers were reviewed to identify cases.9
Two living control infants were
matched to each case infant by postnatal age and community or reservation of
residence. For age matching, AAIMS investigators used a list of eligible American Indian live-born infants by birth date
and selected those born just before and
just after each case. There were 3 refus-
als among the controls, and they were replaced with the next eligible infant with
the closest birth date to the case.
Data Collection
All data were collected retrospectively. Two American Indian nurse interviewers conducted parental interviews using an eighth-grade level,
culturally competent questionnaire that
solicited information about demographic and socioeconomic factors; maternal medical and obstetric history;
neonatal history; and a wide range of
potential risk factors including fetal and
infant exposures.
Mothers were asked about use of cigarettes, alcohol, and illicit drugs during
the 3 months prior to pregnancy, during each trimester, and during the postpartum period. Similarly, mothers were
asked about binge drinking (ⱖ5 drinks
in 1 sitting). The alcohol use questions had been used in the clinical setting prior to the study and were subsequently formally validated in this
population.10
Standardized autopsy protocols were
used. The majority of autopsies were performed by 3 pathologists whose jurisdiction included the study area and who
participated in the study as members of
the steering committee and the PIMR.
Standard death scene investigation protocols were developed and tribal and
county coroners were trained to use
them. Medical records for cases and controls were abstracted and reviewed.
Determination of Cause of Death
The PIMR committee determined the
cause of death for all infants after reviewing all available information. The
committee confirmed a diagnosis of
SIDS only if an autopsy was performed and sufficient information from
the autopsy and scene supported the diagnosis. In the absence of an autopsy,
or if the cause of death was uncertain,
the committee assigned a diagnosis of
“undetermined.”
Statistical Analysis
To assess risk factors for SIDS, we examined characteristics of case and con-
2718 JAMA, December 4, 2002—Vol 288, No. 21 (Reprinted)
trol infants using the ␹2 test for categorical variables and the 2-tailed t tests
for continuous variables and performed a matched conditional logistic
regression using the proportional hazards regression procedure in the Statistical Analysis System. 11 We performed multivariate analyses using
likelihood methods to build models that
included significant factors obtained
from univariate analyses, while taking
into account biological plausibility. We
therefore modeled starting with the 4
most significant independent variables and removing or adding the other
variables to a current model based on
−2 log likelihood. We modeled maternal drinking (any drinking during the
3 months before pregnancy or first trimester in model 1) and binge drinking (first trimester binge drinking in
model 2) separately. We included maternal smoking in the final models given
its significance in other studies. Potential confounders such as maternal age,
education, marital status, and birth
weight were assessed. Interactions between bed sharing or sleep position and
prenatal maternal smoking or alcohol
use, postnatal alcohol use or smoking,
and layers of clothing were examined
and considered significant at P = .10.
Odds ratios (ORs) were considered significant if their 95% confidence intervals (CIs) excluded 1.0 or if the P values were ⬍.05.
RESULTS
Seventy-two deceased American Indian infants younger than 1 year were
enrolled. Autopsy reports were obtained in 56 cases (5 infants whose
deaths were classified as “unexplained” were not autopsied and were
assigned a diagnosis of undetermined;
9 infants whose deaths were “explained” did not have autopsies ordered; and 2 infants whose deaths were
classifed as “infectious” had autopsies
but reports could not be located).
Thirty-seven cases were SIDS, 27 cases
had explained causes (infections, injuries, congenital anomalies), and 8 cases
were undetermined. Among the 37
SIDS cases, 1 parent refused to be in-
©2002 American Medical Association. All rights reserved.
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SIDS AMONG NORTHERN PLAINS INDIANS
terviewed and 3 parents had moved and
could not be located. For the 33 cases
with parental interviews, the death
scene protocol was completed by the
coroner or from police reports in 24
cases, and in 9 cases, summaries of
scene investigations were reviewed by
the PIMR and determined to be compatible with a diagnosis of SIDS.
Data for 66 control infants matched
to the 33 case infants were analyzed.
Five cases and their matching controls were from an urban Indian community and the rest were from rural Indian reservations. The median age
difference between case and control infants was 2 days (range, 0-30 days). The
median interval from the date of death
of the index case to the parental interview was 30 days (range, 8-250 days)
for case infants and 33 days (range,
2-330 days) for control infants.
Characteristics of SIDS Cases
The mean age at death of the SIDS infants was 109 days, 51.5% were male,
and 64.7% died during the autumn and
winter months. We found no significant differences between case and
control infants in the mean values of selected maternal and infant sociodemographic and health care utilization factors, except in mean monthly household
income (TABLE 1).
Univariate Analysis
Sociodemographic and HealthRelated Factors. Parents of SIDS infants were significantly more likely than
control parents to have 12 years of education or less and less likely to have a telephone in the home (TABLE 2). Infants
born to mothers who reported fewer than
7 prenatal visits were at a significantly
increased risk for SIDS as were those
whose mothers reported that inadequate transportation was a barrier. Infants whose mothers reported being visited by a PHN either before or after birth
had a significantly lower risk for SIDS.
Adverse Maternal Behaviors. A
higher percentage of case mothers reported smoking cigarettes during the
3 months prior to pregnancy and during the 3 trimesters than control moth-
Table 1. Mean Values for Selected Sociodemographic and Health-Related Factors
Controls
Cases
Age of mother, y
No.
31
Mean (SD)
24.4 (6.2)
No.
66
Mean (SD)
24.7 (6.0)
P
Value
.86
Age of father, y
Education of mother, y
Education of father, y
29
31
31
26.5 (6.0)
10.9 (1.6)
11.7 (4.3)
60
66
60
28.8 (8.0)
11.2 (2.2)
13.2 (10.5)
.19
.47
.35
Gravidity
Infant birth weight, g
32
32
3.7 (2.0)
3367.2 (503.9)
66
59
2.8 (1.9)
3463.3 (431.1)
.09
.34
Infant gestational age at birth, wk
No. of well-baby visits
No. of prenatal care visits
29
33
32
38.9 (1.9)
2.8 (2.3)
8.9 (5.5)
53
63
64
39.3 (1.3)
3.3 (2.3)
11.1 (5.6)
.07
.27
.07
Monthly household income, $
Crowding index, %*
29
33
723.4 (520.8)
140.7 (151.1)
65
66
986.9 (756.9)
95.9 (56.1)
.05
.11
Variables
*Total number of persons living in the household divided by the total number of rooms in the household times 100.
ers, but these differences were not statistically significant (Table 2). Smoking
rates were high among both cases and
controls with the highest rates during
the 3 months preceding pregnancy, decreasing during each of the subsequent trimesters, and increasing after
delivery to almost prepregnancy levels. Among those who reported smoking during pregnancy, the average number of cigarettes smoked per day did not
vary significantly by case or control status (5.8 vs 6.2 cigarettes per day).
A higher percentage of case mothers reported using alcohol during the
3 months prior to pregnancy and during each trimester than controls (Table
2). The difference in the percentage using alcohol was statistically significant during the first trimester only. Alcohol use for both groups was highest
3 months prior to pregnancy and lowest during the second and third trimester and increased after delivery.
Binge drinking was more common
among case than control mothers, but
the difference was significant only for the
first trimester (Table 2). First trimester
binge drinking was associated with a
6-fold increased risk for SIDS. Rates of
binge drinking decreased during pregnancy, but remained higher among case
mothers than control mothers.
Among drinkers, case mothers consumed an average of 4.5 drinks per day
vs 4.1 for control mothers on the days
that they drank (P⬍.08); case mothers had an average of 1.9 drinking days
©2002 American Medical Association. All rights reserved.
per month vs 1.1 for control mothers
(P⬍.03); and case mothers had an average of 4.8 binge drinking days per trimester vs 2.6 for control mothers
(P⬍.08).
To explore whether the association
between SIDS and maternal binge
drinking reflects differences in maternal nutritional status, we examined maternal pregravid body mass index and
trimester-specific hematocrit and hemoglobin levels. Maternal pregravid
body mass index of less than 25 (69%
of case and 55% of control mothers) was
associated with a small nonsignificant
increased risk for SIDS (OR, 1.8; 95%
CI, 0.6-4.7). Using standard trimesterspecific cut-offs, we compared low vs
high levels of hematocrit (⬍33%,
⬍32%, and ⬍33% for trimesters 1, 2,
and 3, respectively) and hemoglobin
(⬍11.0 g/dL, 10.5 g/dL, and 11.0 g/dL
for trimesters 1, 2, and 3, respectively).
The OR for the association between low
hematocrit values and SIDS progressively decreased from the first through
the third trimester but none were statistically significant (OR, 4.45 [95% CI,
0.24-81.7]; OR, 1.41 [95% CI, 0.267.6]; OR, 0.85 [95% CI, 0.18-4.0]). We
found similar associations between low
hemoglobin levels and SIDS.
About 10% of mothers reported using illicit drugs during pregnancy, but
differences between case and control
mothers were not statistically significant. Marijuana was the most frequently used drug.
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2719
SIDS AMONG NORTHERN PLAINS INDIANS
Table 2. Prevalence of Selected Maternal Sociodemographic, Prenatal, Behavioral, and Newborn Characteristics With Unadjusted Odds Ratios
(ORs) for Sudden Infant Death Syndrome and 95% Confidence Intervals (CIs)
Cases, No. (%)
(n = 33)
Controls, No. (%)
(n = 66)
Unadjusted OR
(95% CI)
4 (12.1)*
6 (18.2)
28 (90.3)*
21 (65.6)*
26 (81.3)*
11 (34.4)*
15 (45.5)
11 (33.3)
22 (68.8)*
6 (9.1)
23 (34.9)
47 (71.2)
31 (47.0)
52 (82.5)†
9 (14.6)†
7 (14.60)
39 (59.1)
34 (55.4)†
1.7 (0.4-7.1)
0.4 (0.2-1.2)
4.2 (1.1-15.5)
2.1 (0.8-5.4)
0.8 (0.3-2.5)
3.3 (1.1-9.8)
11.8 (2.7-52.7)
0.3 (0.1-0.7)
1.8 (0.6-4.7)
17 (51.5)
5 (15.8)*
4 (12.1)
37 (56.1)
8 (13.6)†
5 (7.6)†
0.8 (0.3-1.7)
1.1 (0.3-3.9)
2.1 (0.4-13.1)
29 (93.4)*
11 (33.3)
25 (86.2)*
43 (71.7)†
41 (62.1)
47 (72.3)†
8.8 (1.1-70.8)
0.3 (0.1-0.8)
2.6 (0.8-8.8)
25 (75.8)
22 (66.7)
14 (42.4)
13 (39.4)
23 (69.7)
22 (66.7)
42 (63.6)
34 (51.5)
27 (40.9)
25 (37.9)
36 (54.6)
41 (62.1)
1.9 (0.7-5.0)
2.0 (0.8-4.9)
1.1 (0.4-2.6)
1.1 (0.5-2.4)
2.2 (0.8-5.8)
1.2 (0.5-2.4)
24 (75.0)*
21 (65.6)*
6 (18.8)*
6 (18.8)*
26 (78.8)
37 (59.7)†
17 (27.4)†
6 (9.8)†
4 (6.6)†
38 (57.6)
2.1 (0.7-6.3)
6.7 (2.2-20.1)
2.5 (0.6-10.6)
3.1 (0.7-12.6)
3.4 (1.1-10.7)
19 (59.4)*
15 (46.7)*
5 (15.6)*
6 (18.8)*
24 (72.7)
28 (45.9)†
12 (19.4)†
5 (8.5)†
3 (4.9)†
30 (45.5)
1.9 (0.7-5.0)
6.3 (1.8-22.8)
2.3 (0.5-10.0)
4.5 (0.9-22.9)
3.9 (1.4-10.9)
21 (65.6)*
17 (54.8)*
29 (90.6)*
19 (59.4)*
33 (50.8)†
20 (31.8)†
65 (98.5)
36 (55.4)†
1.9 (0.7-4.9)
13.8 (1.7-109.9)
0.2 (0.0-1.6)
1.1 (0.5-2.6)
5 (15.2)
9 (13.6)
1.3 (0.5-3.3)
Relative to
nonprone
Lateral
Supine
Usually found during the night
Prone
11 (33.3)
17 (51.5)
27 (40.9)
29 (43.9)
7 (21.2)
13 (19.7)
Lateral
Supine
Layers of clothing ⱖ2
Layers of covers ⱖ2
Total clothing + covers ⬎5
8 (24.2)
17 (51.5)
25 (75.8)
23 (69.7)
7 (21.2)
12 (18.2)
38 (57.6)
32 (48.5)
34 (51.5)
6 (9.1)
Variables
Maternal characteristics
Age ⬍18 y
Unmarried
Education ⱕ12 y
Gravida ⬎2
Early prenatal care (trimester 1)
Prenatal care visits ⬍7
Transport problem for prenatal care
Home visit by public health nurse
Maternal prepregnancy body mass index ⬍25
Newborn characteristics
Male sex
Birth weight ⬍3000 g‡
Gestation ⬍37 wk
Other sociodemographic characteristics
Paternal education ⱕ12 y
Telephone in the home
Household income ⬍$15 000 per year
Maternal smoking
3 months before pregnancy
Trimester 1
Trimester 2
Trimester 3
Any smoking during pregnancy
Postnatal
Maternal drinking
3 months before pregnancy
Trimester 1
Trimester 2
Trimester 3
Any drinking during pregnancy
Maternal binge drinking
3 months before pregnancy
Trimester 1
Trimester 2
Trimester 3
Any binge drinking during pregnancy
Infant care
Ever breastfed
Well-baby visits ⬍3
Room sharing with parent
Bed sharing with parent
Usually placed
Prone
1.4 (0.5-3.8)
Relative to
nonprone
3.9 (1.4-10.9)
2.3 (0.9-6.0)
3.6 (0.9-14.5)
*Denominators for some variables are less than 33 because interviews were done with nonbiological primary caretakers and the information was either not available or unreliable.
†Denominators for some variables, especially among controls, were fewer than 66 because mothers “did not know” or refused to answer some questions.
‡A cut-off of ⬍3000 g was used because there was only 1 case infant and no control infants with birth weight ⬍2500 g.
2720 JAMA, December 4, 2002—Vol 288, No. 21 (Reprinted)
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SIDS AMONG NORTHERN PLAINS INDIANS
Infant Sleep Care Factors. More than
half of the infants usually shared a bed
with their parent at night in the 2 weeks
preceding the case infant’s death (Table
2), with similar percentages for case and
control infants. No significant interactions (P=.10) were observed between
usual bed sharing and maternal cigarette smoking or alcohol consumption.
The percentage of infants usually put
to sleep on their stomachs in the 2 weeks
prior to death did not differ between case
and control infants (15.2% vs 13.6%).
The percentages on their sides and backs
were also similar as were the percentages usually found on their stomachs
during the night. No significant interactions (P=.10) were observed between
usual sleep position and cigarette smoking or alcohol consumption during pregnancy or the postpartum period.
Infants who had 2 or more layers of
clothing or covers were at an increased risk for SIDS, although the increase was only statistically significant for infants with 2 or more layers
of clothing (Table 2). No significant interactions (P=.10) were observed between layers of clothing or covers and
usual sleep position or bed sharing.
Those who had fewer than 3 wellbaby visits were at almost 14 times
greater risk for SIDS. Two thirds of case
mothers and half of control mothers reported that they ever breast-fed their infant, but the difference was not statistically significant.
Conditional Logistic Regression
We evaluated the following variables in
a conditional logistic regression model:
maternal education (ⱕ12 years vs ⬎12
years), paternal education (ⱕ12 years
vs ⬎12 years), telephone in the home
(present vs absent), number of prenatal visits (⬍7 vs ⱖ7), maternal smoking during pregnancy (mothers who reported smoking during pregnancy vs
those who did not), layers of clothing
(0-1 vs ⱖ2), periconceptional maternal alcohol use (mothers who reported using alcohol during the 3
months before or the first trimester of
pregnancy vs those that did not), binge
drinking (mothers who reported binge
Table 3. Unadjusted and Adjusted Odds Ratios (ORs) for Sudden Infant Death Syndrome
With 95% Confidence Intervals (CIs), Conditional Logistic Regression
Unadjusted OR
(95% CI)
Adjusted OR*
(95% CI)
3.9 (1.4-10.9)
5.9 (1.9-17.8)
2.2 (0.8-5.8)
6.2 (1.4-26.5)
6.2 (1.6-23.3)
1.3 (0.4-4.7)
0.3 (0.1-0.7)
0.2 (0.1-0.8)
No. of layers of clothing ⱖ2
Binge drinking during trimester 1
Any maternal smoking during pregnancy†
3.9 (1.4-10.9)
6.3 (1.8-22.8)
2.2 (0.8-5.8)
6.2 (1.5-26.1)
8.2 (1.9-35.3)
2.0 (0.6-7.6)
Public health nurse visits, any
0.3 (0.1-0.7)
0.2 (0.1-0.7)
Variable
Model 1
No. of layers of clothing ⱖ2
Periconceptional alcohol drinking
Any maternal smoking during pregnancy†
Public health nurse visits, any
Model 2
*All variables were adjusted for each other.
†Maternal drinking 3 months prior and/or in trimester 1.
drinking during the first trimester vs
those who did not), prenatal or postnatal PHN visit (any vs none) and wellbaby visits (⬍3 vs ⱖ3).
Periconceptional alcohol drinking
(model 1) was associated with an increased risk for SIDS (adjusted OR
[aOR], 6.2; 95% CI, 1.6-23.3) (TABLE 3)
as was first trimester drinking, but the
model fit was slightly better for periconceptional drinking. First trimester
maternal binge drinking (model 2) was
associated with SIDS (aOR, 8.2; 95% CI,
1.9-35.3). Neither binge drinking nor
use of alcohol during the second or
third trimester was associated.
Infants who usually had 2 or more layers of clothing had a greater risk of dying of SIDS than those who had fewer
layers (aOR, 6.2; 95% CI, 1.4-26.5).
When we excluded 4 of 33 matched triplets for which case mothers were interviewed in the winter and control mothers in the summer, the OR fell from 6.2
to 5.2 but remained significant. Infants
whose homes were visited by a PHN had
a significantly lower risk for SIDS than
those who were never visited (aOR, 0.2;
95% CI, 0.1-0.8). Maternal smoking was
associated with an increased risk for
SIDS, but the OR did not reach statistical significance. We found no significant interactions among the risk factors included in the final model.
COMMENT
This study of SIDS among American Indians identified 3 factors that are ame-
©2002 American Medical Association. All rights reserved.
nable to public health action and further research: (1) visits by PHNs, (2)
periconceptional maternal alcohol
drinking and first trimester binge drinking, and (3) infant layers of clothing.
Infants in homes that had any visit
by a PHN before or after birth were onefifth less likely to die of SIDS than those
in homes that were never visited. Public health nursing is an integral component of the IHS programs and is entirely community based. One possible
explanation for the absence of a visit is
inaccessibility. However, nurse visits
were not correlated with reports of
transport barriers to care, the number
of well-baby visits, or the number and
timing of prenatal visits (data not
shown). Further study is needed to confirm the protective effect of PHN visits
and to identify the effective components of outreach activities.
A recent evaluation of home visiting programs concluded that variability in results from one program to another indicates that the benefits of the
programs cannot be generalized.12 Two
randomized controlled trials of home
visitation during the mother’s pregnancy and her child’s first 2 years of life
showed that such visits were associated with positive pregnancy and childhood outcomes.13-15 In another study,
the implementation of a universal postpartum nurse-visiting program resulted in a significant reduction in acute
care visits during the infant’s first 2
weeks of life.16
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2721
SIDS AMONG NORTHERN PLAINS INDIANS
To our knowledge, this is the first
study to report an association between SIDS and periconceptional maternal alcohol consumption and binge
drinking during the first trimester. Few
published studies have reported a relationship between maternal alcohol use
and SIDS, and none of them found an
independent correlation between maternal prenatal alcohol use and the risk
of SIDS.17-19 However, one study did find
a significant association between postnatal maternal alcohol use and SIDS.
One study examined maternal binge
drinking during the month before the
infant’s death but did not find it to be
associated with SIDS.19
The proportion of pregnant control
mothers reporting alcohol use during
the third trimester in the AAIMS (6.6%)
is similar to the proportion of mothers
in the AAIHS (6.3%) who reported
drinking during pregnancy on birth certificates in 1994-1996.8 The proportion is 4.5% for all IHS areas and 1.5%
for all races in the United States.
In our study population, the pattern of drinking is predominantly binge
drinking, and the OR for maternal binge
drinking and SIDS was highest during
the first trimester. Craniofacial anomalies, low birth weight, decreased head
circumference, and congenital anomalies have been correlated with alcohol
exposure in the first trimester in other
studies.20-22 However, in this study, none
of the infants who died had microcephaly, craniofacial anomalies, or major brain malformations. We also found
no evidence to suggest that the association between alcohol and SIDS is mediated by poor prenatal maternal nutritional status.
In addition, by definition, assignment of the SIDS diagnosis meant that
there was no evidence of abuse or neglect associated with excessive postnatal alcohol consumption. More research is needed to confirm these
findings and elucidate the pathways
leading to increased risk.
Excess thermal insulation for a given
room temperature has been associated
with increased SIDS risk,23,24 and the risk
is further increased by viral illness25 and
prone sleep position.24 We found that
usually wearing 2 or more layers of
clothing at night, not including the diaper, increased an infant’s risk for SIDS
more than 6-fold. Neither the number
of covers nor the type (thin or thick blanket, sheet, quilt, or comforter) was significantly associated with SIDS risk.
Bed sharing in combination with maternal smoking during pregnancy has
been shown to be associated with an increased risk for SIDS.19,26-28 This increased risk is also associated with other
risk factors, ie, recent maternal alcohol
consumption, the infant being covered
by a duvet, and parental tiredness.28 Bed
sharing is routine among Northern Plains
Indians. While we did not observe significant interactions between bed sharing and cigarette smoking or alcohol consumption, this study may lack the power
to adequately assess the relationship of
bed sharing to other risk factors.
The primary limitation of the study
is the small sample size. The study had
a 40% power to detect a 2-fold difference in smoking between case and control mothers and a 42% power to detect a 2-fold difference in gestational age
between case and control infants. However, despite the small sample size, positive associations of potentially modifiable contributors to SIDS were found,
although CIs were wide.
Another limitation is that the standard death scene form was not completed on all unattended deaths in spite
of the availability of formal coroner
training programs. Tribal police investigated half of the deaths because there
was no enabling tribal legislation for
coroners. The PIMR reviewed coroner, police, and emergency medical
technician reports. When written reports of the scene investigation were not
provided, the personnel who investigated the deaths were interviewed for
information on possible homicide, overlying, or other diagnoses.
Recall bias regarding events during
pregnancy or around the time of infant death is another potential limitation. However, it is unlikely that differential maternal recall bias between
cases and controls occurred because of
2722 JAMA, December 4, 2002—Vol 288, No. 21 (Reprinted)
the high self-reported rates of smoking and alcohol use and the similar interval between death and interview of
the cases and controls. Other casecontrol SIDS studies that examined recall bias did not find an appreciable impact on the important associations.29-30
Our results provide new evidence
that factors in the periconceptional period contribute to SIDS risk in addition to those identified in the prenatal
and postnatal periods. They suggest that
public health outreach and programs
to reduce alcohol consumption among
women of childbearing age could have
an impact on SIDS rates in this population.
Author Contributions: Study concept and design:
Iyasu, L. Randall, Welty, Kinney, B. Randall, Wilson,
Willinger.
Acquisition of data: L. Randall, Welty, Kinney,
B. Randall, Wilson, Habbe.
Analysis and interpretation of data: Iyasu, Welty, Hsia,
Kinney, Mandell, McClain, Willinger.
Drafting of the manuscript: Iyasu, Welty, Wilson,
Willinger.
Critical revision of the manuscript for important intellectual content: Iyasu, L. Randall, Welty, Hsia,
Kinney, Mandell, McClain, B. Randall, Habbe, Willinger.
Statistical expertise: Iyasu, Hsia.
Obtained funding: Iyasu, Welty, Kinney, Willinger.
Administrative, technical, or material support: Iyasu,
L. Randall, Welty, Kinney, Habbe.
Study supervision: Iyasu, Welty, Willinger.
Funding/Support: This study was funded by the National Institute of Child Health and Human Development, the Centers for Disease Control and Prevention, and the Indian Health Service through interagency
agreements. The study would not have been possible without the collaboration and support provided
by the Aberdeen Area Tribal Chairmen’s Health Board
and the 10 participating tribal communities.
Acknowledgment: We would like to thank the Steering Committee for the study and the Perinatal Infant
Mortality Review Committee for their guidance and contributions to the study and the staff at the Centers for
Disease Control and Prevention and the office of Epidemiology, Aberdeen Area Indian Health Service, and
the many families who participated in the study.
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11. SAS Institute, Inc. SAS/STAT Software: Changes
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12. Gomby DS, Culross PL, Behrman RE. Home visiting: recent program evaluations—analysis and recommendations. Future Child. 1999;9:4-26.
13. Olds DL, Henderson CR, Tatelbaum R, Chamberlin R. Improving the delivery of prenatal care and
outcomes of pregnancy: a randomized trial of nurse
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14. Olds DL, Henderson CR, Chamberlin R, Tatelbaum R. Preventing child abuse and neglect: a randomized controlled trial of home visitation. Pediatrics. 1986;78:65-78.
15. Kitzman H, Olds DL, Henderson CR, et al. Effect
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16. Braveman P, Miller C, Egerter S, et al. Health service use among low-risk newborns after early discharge with and without nurse home visiting. J Am
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Wisdom is not acquired save as the result of investigation.
—Sankara Acharya (c 769-820)
©2002 American Medical Association. All rights reserved.
(Reprinted) JAMA, December 4, 2002—Vol 288, No. 21
Downloaded from www.jama.com at Medical Library of the PLA, on August 14, 2007
2723
LETTERS
obstructed sinuses bilaterally in all patients. Interestingly, one
of the patients had surgery during the course of this study, and
in this patient nasal nitric oxide levels increased during humming to almost normal levels 2 weeks after the operation (data
not shown).
It is possible that it is the actual production of nitric oxide
that is reduced in the patients with nasal polyposis. However,
this seems less likely since nasal nitric oxide levels during quiet
breathing were not significantly reduced in the patients in this
study. Also, in an earlier study, levels of nasal nitric oxide were
only somewhat lower in patients with nonallergic polyposis and
normal in those with allergic polyposis.6 Although the humming test presented here appears promising, it should not be
used in the clinical situation until further studies establish its
sensitivity and specificity.
Jon O. Lundberg, MD, PhD
Department of Physiology and Pharmacology
Mauro Maniscalo, MD
Department of Physiology and Pharmacology
Karolinska Institute
Stockholm, Sweden
Matteo Sofia, MD, PhD
Department of Respiratory Medicine
University Frederico II
Naples, Italy
Lars Lundblad, MD, PhD
Department of Surgical Science
Eddie Weitzberg, MD, PhD
Department of Otorhinolaryngology
Karolinska Hospital
Stockholm
Financial Disclosure: Drs Lundberg and Weitzberg own shares in Aerocrine AB,
which manufactures a system for measuring exhaled nitric oxide.
Funding/Support: This study was supported by grants from the Swedish HeartLung Foundation, the Vårdal Foundation, and the Swedish Research Council. The
foundations had no role in the study design or in its writing.
1. Hamilos D. Chronic sinusitis. J Allergy Clin Immunol. 2000;106:213-227.
2. Lundberg JO, Weitzberg E, Nordvall SL, Kuylenstierna R, Lundberg JM, Alving
K. Primarily nasal origin of exhaled nitric oxide and absence in Kartagener’s syndrome. Eur Respir J. 1994;7:1501-1504.
3. Lundberg JO, Farkas-Szallasi T, Weitzberg E, et al. High nitric oxide production in human paranasal sinuses. Nature Med. 1995;1:370-373.
4. Weitzberg E, Lundberg JO. Humming greatly increases nasal nitric oxide. Am
J Respir Crit Care Med. 2002;166:144-145.
5. American Thoracic Society. Recommendations for standardized procedures for
online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide in adults and children. Am J Respir Crit Care Med. 1999;160:21042117.
6. Arnal J, Flores P, Rami J, et al. Nasal nitric oxide concentrations in paranasal
sinus inflammatory diseases. Eur Respir J. 1999;13:307-312.
CORRECTION
Incorrect Wording: In the Original Contribution entitled “Risk Factors for Sudden Infant Death Syndrome Among Northern Plains Indians” published in the December 4, 2002, issue of THE JOURNAL, there was incorrect wording. In the “Comment” section on page 2721, the first sentence of the second paragraph should
have read as follows: Infants in homes that had any visit by a PHN before or after
birth were one-fifth as likely to die of SIDS as those in homes that were never
visited.
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