



* Departments of Pediatrics and Epidemiology and Biostatistics, Boston University Schools of Medicine and Public Health, Boston, Massachusetts
Slone Epidemiology Unit, School of Public Health, Boston University School of Medicine, Boston, Massachusetts
Department of Pediatrics, Medical College of Ohio, Toledo, Ohio
|| Massachusetts Center for Sudden Infant Death Syndrome, Boston, Massachusetts
| ABSTRACT |
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Methods. A prospective cohort study was conducted in eastern Massachusetts and northwest Ohio of 12 029 mothers of infants who weighed
2500 g at birth. Descriptive statistics and multivariate odds ratios were used to relate maternal and infant characteristics to prone and supine sleeping.
Results. A total of 14 206 mothers (25% of those eligible) were enrolled. A total of 12 029 mothers (85% of enrolled) responded to the 1-month and 11 552 mothers (81% of enrolled) responded to the 3-month follow-up questionnaire. A decline in use of the prone sleep position and increase in use of the supine position was observed during the 4 years of the study. Factors associated with prone and supine sleep position were similar in 19951996 and 19971998. In 19971998, use of prone sleeping at 1 month of age reached the goal of
10% only among infants of white and Asian women, married women, women who were older than 25 years, women who were college graduates, and women with incomes >$55 000 per year. At 3 months of age, however, prone sleeping increased to 12% to 17% in these groups. These same groups were most likely to use the supine position; 38% to 45% were supine at 1 month, increasing to 56% to 64% by 3 months of age. However, as of the end of 1998, approximately 27% of infants of non-college-educated black and Hispanic mothers were placed to sleep in the prone position and only 20% to 30% were being placed to sleep in the supine position at 3 months of age.
Conclusions. Recommendations to avoid prone sleep position and especially the recommendation that supine sleep position is preferred have not been effectively delivered to black and Hispanic families and to families of low-income and less than a college education.
Key Words: infant sleep position sudden infant death syndrome Back to Sleep racial disparities
Abbreviations: SIDS, sudden infant death syndrome
| INTRODUCTION |
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In April 1992, the American Academy of Pediatrics recommended that healthy newborns be placed on their side or back to sleep, and in 1994, the Back to Sleep campaign was initiated in the United States by a joint statement of the American Academy of Pediatrics, several government agencies, and SIDS organizations. In 1996, the recommendations were amended to emphasize supine sleep position as the preferred position. The goal of the Back to Sleep effort is to reduce the prevalence of prone sleeping among infants to 10% or less.14 Annual telephone surveys of households with infants younger than 8 months indicate that the average prevalence of prone sleeping in this age group decreased from 70% in 1992 to 17% in 1998 and that the prevalence of prone sleeping was higher among blacks and older infants.15 We have previously reported that in 1995 and 1996 nearly 30% of US infants slept prone at 3 months of age and that a substantial proportion of infants slept nonprone early but changed to prone by 3 months.16 These reports and others have identified a number of characteristics associated with increased risk of prone sleep position, including maternal race and education. What is not clear from these reports, however, is whether characteristics associated with choice of sleep position have changed over time and how these factors are related to secular changes in infant sleep position. The purpose of the current report is to compare factors associated with sleep position in 19951996 and 19971998 and to assess secular trends in the use of prone infant sleep position from 1995 through 1998 among families according to race and education.
| METHODS |
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Statistical Methods
The
2 test was used to compare proportions across groups defined by time or demographic variables. The paired sample
2 test was used to compare changes in proportions within a group over time. Percentages in the prone sleep position were compared with the targeted 10% through the
2 goodness-of-fit test. Multiple logistic regression was used to evaluate potential risk factors (predictors) for sleep position while controlling for the potential confounding effects of other factors.17 Indicator terms were included in the logistic regression models for the following: race/ethnicity, maternal age, marital status, parity, education, smoking while pregnant, annual household income, infants gender and postnatal age, breastfeeding, and calendar time. Associations are described with adjusted odds ratios and their 95% confidence intervals. Plots were made to show secular trends in 1- and 3-month sleep position within the following 4 strata based on maternal race/ethnicity and education: 1) white, college graduate; 2) white, non-college graduate; 3) black/Hispanic, college graduate; and 4) black/Hispanic, non-college graduate. Black and Hispanic families were pooled in the stratified analysis because the trends were similar in these families and to ensure that each stratum was large enough to assess secular trends. There were not a sufficient number of Asian families to include in this stratified analysis. Smoothing was performed using a 9-month moving average centered on each calendar quarter. A Mantel-Haenszel
2 test for trend was used to assess changes in sleep position over calendar time.18 Assessment of factors associated with sleep position was limited to the 1- and 3-month data, because 6 months of age is beyond the period of highest risk for SIDS.
| RESULTS |
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2). At 1 month of age, the proportion of infants who slept prone declined from 18% in 19951996 to 12% in 19971998 (P < .001), with supine sleep position increasing from 18% to 36% (P < .001). Side sleep position was most common at 1 month of age, used by 49% of infants in 19971998. In 19971998, 52% of 3-month-old infants were placed to sleep in the supine position; however, 20% were still being placed in the prone position.
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At 1 month of age, the use of prone sleeping failed to reach the goal of
10% among infants in any groups in 19951996, but by 19971998, the goal was reached among infants of white and Asian women, women who were older than 25 years, married women, women who were college graduates, and women with household incomes >$55 000 per year. At 3 months of age, however, prone sleeping rose to 12% to 17% in these groups (P < .05 for each by paired sample
2 test). Similarly, in 19971998, women with these characteristics were more likely to place their infants to sleep in the supine position; 39% to 45% supine at 1 month, rising to 58% to 64% supine at 3 months of age (P < .001 for all groups).
The secular trend in prone and supine sleep position at 1 and 3 months of age, stratified by race and education, is shown in Fig 2. During the 4 years from early 1995 to the end of 1998, prone sleeping at 1 month of age declined in all strata (P < .01 in all strata). However, black/Hispanic non-college graduates did not sustain this decline through 1998 (test for trend over 19971998 was not significant, P = .9) and was the only stratum that did not approach the target of <10% prone sleeping; during the last 6 months of 1998, prone sleeping was used by 21% of black/Hispanic non-college graduates, a figure that is significantly more than 10% (P < .001). During this same period, prone sleeping was used by 3% of white college graduates (a figure that is significantly less than 10%, P < .001), 11% of black/Hispanic college graduates, and 9% of white non-college graduates (figures that are not significantly different from 10%). Similarly, use of supine sleep position at 1 month of age increased in all strata (P < .001 for test of trend in all strata); however, at the end of 1998, black/Hispanic non-college graduates had the lowest level of supine sleep at 1 month of age (P < .001 for each pair-wise comparison). Prone sleeping at 3 months of age declined in all strata (P < .01 for test of trend in all strata), but only infants of college-educated white mothers came close to the goal of
10% (11% in the last 6 months of 1998, not significantly different from 10%), whereas in each of the other strata, even among infants enrolled at the end of 1998, 18% to 27% of 3-month-old infants were reported as sleeping prone (significantly >10%, P < .05 for all strata). Similarly, supine sleep position at 3 months of age increased in all strata (P < .001 for test of trend in all strata). However, during the last 6 months of 1998, supine sleeping was markedly less for black/Hispanic non-college graduates (34%) than for the other 3 strata (59%; P < .001 for each pair-wise comparison).
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| DISCUSSION |
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These data are consistent with the US national telephone survey that indicates the prevalence of prone sleeping has declined from 44% to 17% and supine sleeping increased from 17% to 51% between 1994 and 1998.15 These data are also consistent with reports indicating that black and low-income families are more likely to place their infants to sleep in the prone position.13,15,1921 However, the present study includes a larger sample of minority infants than earlier reports, resulting in more stable estimates and permitting the detection of significant associations between race/ethnicity and prone sleeping. Because the present study enrolled a representative sample of all women who delivered a child at a participating hospital, our data are also less subject to selection bias than telephone surveys, which by definition are limited to households with telephones. Furthermore, the unique longitudinal design of this study provides an opportunity to observe changes in sleep position as children grow and to identify those infants who change to the prone position between 1 and 3 months.
There are several limitations to these data. Sleep position was based on maternal description, not direct observation. Mothers were enrolled only in eastern Massachusetts and northwest Ohio and compared with the US population; a higher proportion of study mothers had some postsecondary education. As such, these women may not be representative of all US women who gave birth during this time. In particular, the Hispanic women in our study were predominantly of Puerto Rican origin and may not reflect attitudes and behaviors of other Hispanic groups (eg, Mexican Americans), and the total number of Asian women (predominantly of Southeast Asian origin) was small. In addition, it is possible that the rate of supine sleeping overall may be lower in other areas of the United States because the subjects of this report had an overrepresentation of college-educated women, a predictor for supine sleeping.
| CONCLUSION |
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10% of infants sleeping prone was achieved in 1998 only among infants of white, college-educated, and older mothers; however, the rate of prone sleeping remains >20% among infants of mothers who are black and Hispanic non-college graduates. In addition, the prevalence of prone sleeping at 3 months of age remains in the range of 18% to 27% for infants of black and Hispanic mothers and non-college-educated white mothers. In 19971998, side sleep position continued to be most common among infants at 1 month of age, many of these changing to either supine or prone sleeping by 3 months of age. In addition, the factors associated with increased risk of prone sleeping and decreased likelihood of supine position have not changed substantially between 1995 and 1998. Therefore, it seems reasonable that efforts intended to reduce further the prevalence of prone sleeping should be designed to target the population groups that are at particular risk for this practice. It also seems clear that increased emphasis on supine sleeping may be warranted, especially for the groups that have been least likely to use this position. In virtually all other countries where a public health intervention has been undertaken to change infants sleep position, the prevalence of prone sleeping has decreased substantially and is now generally below 10%.6,2227 The challenge that remains is to design or identify strategies that will have a comparable benefit among high-risk groups in the United States.
| ACKNOWLEDGMENTS |
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We thank Sandra Hatfield, Dottie Powers, and Debra Zagaeski for research assistance; Maria Francescon, Patricia Brousseau, Chris DeArmond, Cynthia Nagle, Heather Wightmann, and Grace Adeya for recruiting patients and conducting the interviews; Paul Paslaski and Leonard Gaetano for programming assistance; and Theodore Colton, ScD, for advice on study design and data analysis. We are indebted to the physicians and nurses at the following hospitals: Boston Medical Center and the Beth Israel Hospital (Boston, MA), Lowell General Hospital (Lowell, MA), Lawrence General Hospital (Lawrence, MA), and St Vincent Mercy Medical Center and Toledo Hospital (Toledo, OH).
| FOOTNOTES |
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Reprint requests to (M.J.C.) Department of Pediatrics, Boston Medical Center, One Boston Medical Center Pl, Boston, MA 02118. E-mail: mjcorwin{at}bu.edu
Dr Hunt is currently at the Center on Sleep Disorders Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, and mention of trade names, commercial products, or organizations does not imply endorsement by the US government.
| REFERENCES |
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