Postneonatal Mortality Among Alaska Native Infants — Alaska, 1989–2009

Alaska's postneonatal mortality rate of 3.4 deaths per 1,000 live births during 2006–2008 was 48% higher than the 2007 U.S. rate of 2.3 per 1,000 (1,2). Among American Indian/Alaska Native (AI/AN) infants, the Alaska rate of 8.0 per 1,000 was 70% higher than the U.S. rate of 4.7. The Alaska Division of Public Health analyzed a linked birth-infant death file for 1989–2009 to examine temporal trends in postneonatal mortality in Alaska, specifically in the Alaska Native (AN) population. Overall and non-Alaska Native (non-AN) rates declined during the entire period, but no significant trends in AN-specific mortality were apparent. Infant mortality review committee findings indicated a decline during 1992–2007 among all postneonatal deaths attributed to sudden infant death syndrome (SIDS) or sudden unexplained infant death (SUID), but not for other causes. Lack of progress in reducing postneonatal mortality, particularly among AN infants, indicates a need for renewed emphasis within the Alaska health-care community. Current initiatives to reduce preventable causes of postneonatal mortality should be evaluated and successful models more widely implemented.

The Alaska Bureau of Vital Statistics provided an electronic file with linked records for the 222,317 recorded live births and 821 postneonatal deaths among infants aged 28–364 days born to Alaska residents during 1989–2009. Potential risk factors for infant mortality that might be determined from information included on birth certificates were identified through prior research and literature review. Those risk factors included infant birth weight and gestational age; maternal race, years of education, age, and prenatal cigarette, smokeless tobacco, and alcohol use; and a composite variable reflecting maternal marital status and presence of a father's name on the birth certificate (1,3). Race was categorized as AN, which included all indigenous groups, or non-AN, based on mother's race.

For the analysis, logistic regression modeling was conducted, as was joinpoint testing for significance of trends and to detect significant points of change in the slope of linear trends. In joinpoint, the permutation test was used, and log-linear models created to calculate annual percent change (APC) in the linear trend of mortality rates. Average annual percentage change (AAPC) was calculated to summarize and compare trends in the prevalences of risk factors among births during 2000–2009 (4). Cause of death was obtained from the Alaska Maternal Infant Mortality Review (MIMR), a committee coordinated by the Alaska Division of Public Health and consisting of private physicians, nurses, and other child health experts. At the time of this report, the MIMR committee had reviewed medical records, autopsy reports, police reports, and other records for >99% of Alaskan postneonatal deaths that occurred during 1992–2007 and issued findings regarding causes and contributing factors to the deaths and preventability recommendations.

Overall postneonatal mortality declined from 4.9 deaths per 1,000 births in 1989 to 3.9 in 2009 (APC = -2.2; 95% confidence interval [CI] = -3.3 to -1.0). The non-AN rate also declined during the study period (APC = -2.8; CI = -4.5 to -1.1), although annual rates fluctuated (Figure). Among non-AN, 1989 and 2009 rates were identical (3.0 per 1,000 births), yet joinpoint analysis selected a single declining slope as the best fit linear trend for the entire study period. No significant trends in AN mortality rates were apparent (APC = -1.5; CI = -3.6 to 0.6), and no significant changes in slope were identified. The AN rate was higher than the non-AN rate during the first half and the second half of the study period (1989–1999 rate ratio [RR] = 2.4; CI = 2.0 – 2.9; 2000–2009 RR = 3.1; CI = 2.5 – 3.9).

Among AN infants, significant bivariate risk factors for postneonatal mortality during 2000–2009 included preterm birth (RR for birth at <34 weeks = 4.6; RR for birth at 34–36 weeks = 1.9) and low birth weight (RR = 3.8), unmarried mother with no father indicated (RR = 3.5), maternal prenatal alcohol and cigarette use (RR = 2.2 and 1.9, respectively), and maternal education <12 years (RR = 1.6) (Table 1). In a multivariate logistic regression model containing education, cigarette use, alcohol use, and partner status, education was no longer significant and therefore was dropped from the final model. The prevalence of AN births to unmarried mothers with no father indicated on the birth certificate increased during 2000–2009 (AAPC = 7.3; CI = 4.1 to 10.6).

Cause-specific mortality rates, allowing for multiple causes of death, were calculated for 4-year intervals because of the small numbers of events (Table 2). The overall postneonatal mortality rate for SIDS or SUID declined from 2.2 per 1,000 births during 1992–1995 to 1.4 per 1,000 during 2004–2007 (APC = -13.3; CI = -24.3 to -0.7), but no trends were observed for other causes. Less than five postneonatal deaths during 1992–1995 were attributed to preterm birth or perinatal events, compared with 11 or more deaths related to preterm birth during other 4-year periods and 10 perinatal event-related deaths during 2004–2007. Among AN infants only, no cause-specific trends were significant.

Reported by

Margaret B. Young, MPH, Bradford D. Gessner, MD, Alaska Division of Public Health. Corresponding contributor: Margaret B. Young, margaret.young@alaska.gov, 907-269-5657.

Editorial Note

Postneonatal mortality often is related to exposure to environmental risks and family socioeconomic characteristics, and thus, in theory, should be preventable (3). Although mortality rates declined among the non-AN population, AN postneonatal mortality rates did not show a significant trend. Postneonatal mortality for the United States declined from 3.2 deaths per 1,000 live births in 1990 to 2.3 in 2000; however, as in Alaska, no improvements have occurred since, either overall or specifically for AI/AN children (1,5).

The decrease in mortality caused by SIDS and SUID is encouraging because both account for a large proportion of postneonatal deaths among the overall population (1). Some of this decrease might be attributable to the Back to Sleep* public education campaign, which was initiated in Alaska in 1996. However, this result might have resulted, in part, from a diagnostic shift whereby deaths during later years were assigned to different causes (6). The greater number of deaths attributed to preterm birth and perinatal events during the later years might have resulted from a greater likelihood of survival outside the neonatal period, combined with a small increase in the prevalence of preterm births at <37 weeks among non-AN (mostly for births at 34–36 weeks). A lack of decline in the overall U.S. infant mortality rate during 2000–2005 has been attributed to increases in preterm births and preterm-related mortality (7).

Prior research identified three independent factors that are associated with increased postneonatal mortality among AN compared with non-AN infants in Alaska: low maternal education, any prenatal substance use, and unmarried marital status combined with the lack of a father's name on the birth certificate (3). The prevalence of the latter among AN births increased during 2000–2009, and these infants were three times more likely to die in the postneonatal period than infants with a father listed or a married mother. Maternal substance use, particularly tobacco and alcohol, has been associated with SIDS and SUID, and the high prevalence of these factors combined with the lack of decline among AN births might be one factor in the lack of decline of SIDS and SUID mortality among AN infants. AN infants also might have additional risk factors that were not measured. For example, preliminary evidence suggests that carnitine palmitoyltransferase type 1A deficiency, a fatty acid disorder highly prevalent in AN and other indigenous circumpolar populations, might contribute to infant mortality (8).

The findings in this report are subject to at least three limitations. First, the small annual number of postneonatal deaths in Alaska complicates interpretation and identification of factors influencing yearly changes in rates. Annual rates are presented here to increase the information available for examining trends; however, rates based on fewer than 20 occurrences are statistically unreliable and should be used with caution. Second, information on risk factors and cause of death might be biased and incomplete. Birth certificates might provide unreliable data on prenatal substance use (9). Prenatal care was not included as a risk factor because of suspected misclassification and reporting issues, particularly for rural Alaska. The significance of marital status and presence of a father's name on the birth certificate has limitations related to interpretability and misclassification, and the meaning might vary by cultural group (3). Finally, MIMR data are subject to potential bias resulting from changes in committee membership and the knowledge and expertise of individual members. However, the information available from MIMR on each case was comprehensive and might more accurately indicate cause of death than death certificate data (6,10).

To address Alaska's high overall postneonatal mortality and infant deaths related to SIDS and SUID or unintentional suffocation, the Alaska Division of Public Health launched an Infant Safe Sleep Initiative in 2009, and research is ongoing to support an associated statewide social marketing campaign to begin in 2012. This initiative builds on SIDS and SUID prevention work already begun by the national Healthy Native Babies Project,† and ongoing work by tribal health organizations and others in Alaska. The Division also is awarding contracts for the Healthy Start and Maternal, Infant, and Early Childhood Home Visiting programs to Alaskan agencies that will start activities in early 2012 to address infant health outcomes, including mortality and safe sleep. Healthy Start also targets factors that contribute to preterm birth, such as tobacco use. Studies are underway to explore the effect on mortality of modifiable conditions, such as carnitine palmitoyltransferase type 1A deficiency, which might assist in targeting interventions. Future evaluations of these projects, especially in AN communities, could provide further evidence to understand the underlying causes of the persistent disparity between AN and non-AN in postneonatal mortality rates, and reasons for the lack of progress in reducing AN mortality.

References

1. Mathews TJ, MacDorman MF. Infant mortality statistics from the 2007 period linked birth/infant death data set. Natl Vital Stat Rep 2011;59(6).
2. Alaska Bureau of Vital Statistics. 2008 annual report. Juneau, AK: Alaska Department of Health and Social Services, Division of Public Health, Bureau of Vital Statistics; 2009. Available at http://www.hss.state.ak.us/dph/bvs/data/2008ar.htm. Accessed January 5, 2012.
3. Blabey MH, Gessner BD. Three maternal risk factors associated with elevated risk of postneonatal mortality among Alaska Native population. Matern Child Health J 2009;13:222–30.
4. Clegg LX, Hankey BF, Tiwari R, Feuer EJ, Edwards BK. Estimating average annual per cent change in trend analysis. Stat Med 2009;28:3670–82.
5. National Center for Health Statistics. Health, United States, 2010: with special feature on death and dying. Hyattsville, MD: US Department of Health and Human Services, CDC, National Center for Health Statistics; 2011. Available at http://www.cdc.gov/nchs/hus.htm. Accessed January 6, 2012.
6. Shapiro-Mendoza CK, Tomashek KM, Anderson RN, Wingo J. Recent national trends in sudden, unexpected infant deaths: more evidence supporting a change in classification or reporting. Am J Epidemiol 2006;163:762–9.
7. MacDorman MF, Mathews TJ. Recent trends in infant mortality in the United States. NCHS Data Brief No 9. Hyattsville, MD: US Department of Health and Human Services, CDC, National Center for Health Statistics; 2008. Available at http://www.cdc.gov/nchs/data/databriefs/db09.htm. Accessed January 6, 2012.
8. Gessner BD, Gillingham MB, Birch S, Wood T, Koeller DM. Evidence for an association between infant mortality and a carnitine palmitoyltransferase 1A genetic variant. Pediatrics 2010;126:945–51.
9. Northam S, Knapp TR. The reliability and validity of birth certificates. J Obstet Gynecol Neonatal Nurs 2006;35:3–12.
10. CDC. Misclassification of infant deaths—Alaska, 1990–1991. MMWR 1992;41:584–5,591.