Differences in cause-specific infant mortality among Chinese, Japanese, and white Americans

Advancing Health Disparities Research: The Need to Include Asian American Subgroup Populations

BACKGROUND

Despite recognition that the health outcomes of Asian American subgroups are heterogeneous, research has mainly focused on the six largest subgroups. There is limited knowledge of smaller subgroups and their health outcomes. This scoping review identifies trends in the health outcomes, reveals those which are under-researched, and provide recommendations on data collection with 24 Asian American subgroups.

METHODS

Our literature search of peer-reviewed English language primary source articles published between 1991 and 2018 was conducted across six databases (Embase, PubMed, Web of Sciences, CINAHL, PsychINFO, Academic Search Complete) and Google Scholar, yielding 3844 articles. After duplicate removal, we independently screened 3413 studies to determine whether they met inclusion criteria. Seventy-six studies were identified for inclusion in this review. Data were extracted on study characteristics, content, and findings.

FINDINGS

Seventy-six studies met the inclusion criteria. The most represented subgroups were Chinese (n = 74), Japanese (n = 60), and Filipino (n = 60), while Indonesian (n = 1), Malaysian (n = 1), and Burmese (n = 1) were included in only one or two studies. Several Asian American subgroups listed in the 2010 U.S. Census were not represented in any of the studies. Overall, the most studied health conditions were cancer (n = 29), diabetes (n = 13), maternal and infant health (n = 10), and cardiovascular disease (n = 9). Studies showed that health outcomes varied greatly across subgroups.

CONCLUSIONS

More research is required to focus on smaller-sized subgroup populations to obtain accurate results and address health disparities for all groups.

Association of Low Birthweight and Indoor Air Pollution: Biomass Fuel Use in Bangladesh

BACKGROUND

More than 90% of all low birthweight (LBW) babies are born in developing countries, and half of the population in developing nations uses solid fuels as their primary source of energy for cooking. An association between household use of solid biomass fuels and reduced newborn weight has been found in a number of countries. Bangladesh has a high prevalence of LBW babies (22%), and 88% of the population use solid fuels for cooking.

OBJECTIVES

This study aims to explore whether indoor air pollution is associated with LBW in Bangladesh, an important determinant of infant mortality and morbidity.

METHODS

The 2011 Bangladesh Demographic and Health Survey (BDHS) was used for the present analysis. The total number of births reported in the previous five years by respondents in the survey sample was 8,753. Mothers' recall of their baby's weight was the dependent dichotomous variable. A mixed effects logistic regression model was fitted using region as a random effect and several independent fixed effects.

RESULTS

High pollutant cooking fuels, such as coal and wood, resulted in higher odds of having a LBW child compared to use of electricity/gas (odds ratio (OR): 2.6, confidence interval (CI): 1.1-6.2 and OR: 1.1, CI: 1.0-1.2). Factors which lowered the odds include mothers with a bachelor's degree or higher education (OR: 0.6, CI: 0.4-0.9), third order children (OR: 0.8, CI: 0.6-0.9), fourth or higher order children (OR: 0.8, CI: 0.6-1.0), having a male child (OR: 0.7, CI: 0.7-0.8), and receiving sufficient antenatal care (OR: 0.8, CI: 0.6-0.9). Factors which increase the odds of having a LBW infant include mothers who are underweight compared to normal weight mothers (OR: 1.1, CI: 1.1-1.2), mistimed pregnancies (OR: 1.2, CI: 1.0-1.4), or unplanned pregnancies (OR: 1.3, CI: 1.0-1.7), compared to planned pregnancies.

CONCLUSIONS

This is the first paper to show an association between use of highly pollutant biomass fuel and prevalence of LBW babies in Bangladesh, suggesting that besides polluting the air and causing respiratory illnesses, biomass fuel combustion may also affect the health of fetuses in utero. Further longitudinal studies are required to establish this finding among mothers in developing countries.

The differential association between education and infant mortality by nativity status of Chinese American mothers: a life-course perspective

OBJECTIVES

Integrating evidence from demography and epidemiology, we investigated whether the association between maternal achieved status (education) and infant mortality differed by maternal place of origin (nativity) over the life course of Chinese Americans.

METHODS

We conducted a population-based cohort study of singleton live births to US-resident Chinese American mothers using National Center for Health Statistics 1995 to 2000 linked live birth and infant death cohort files. We categorized mothers by nativity (US born [n = 15 040] or foreign born [n = 150 620]) and education (≥ 16 years, 13-15 years, or ≤ 12 years), forming 6 life-course trajectories. We performed Cox proportional hazards regressions of infant mortality.

RESULTS

We found significant nativity-by-education interaction via stratified analyses and testing interaction terms (P < .03) and substantial differentials in infant mortality across divergent maternal life-course trajectories. Low education was more detrimental for the US born, with the highest risk among US-born mothers with 12 years or less of education (adjusted hazard ratio = 2.39; 95% confidence interval = 1.33, 4.27).

CONCLUSIONS

Maternal nativity and education synergistically affect infant mortality among Chinese Americans, suggesting the importance of searching for potential mechanisms over the maternal life course and targeting identified high-risk groups and potential downward mobility.

Differences in neonatal mortality among whites and Asian American subgroups: evidence from California

OBJECTIVE

To obtain information about health outcomes in neonates in 9 subgroups of the Asian population in the United States.

DESIGN

Cross-sectional comparison of outcomes for births to mothers of Cambodian, Chinese, Filipino, Indian, Japanese, Korean, Laotian, Thai, and Vietnamese origin and for births to non-Hispanic white mothers. Regression models were used to compare neonatal mortality across groups before and after controlling for various risk factors.

SETTING

All California births between January 1,1991, and December 31, 2001.

PARTICIPANTS

More than 2.3 million newborn infants.

MAIN EXPOSURE

Racial and ethnic groups.

MAIN OUTCOME MEASURE

Neonatal mortality (death within 28 days of birth).

RESULTS

The unadjusted mortality rate for births to non-Hispanic white mothers was 2.0 per 1000. The unadjusted mortality rate for births to Chinese and Japanese mothers was significantly lower (Chinese: 1.2 per 1000, P<.001; Japanese: 1.2 per 1000, P=.004), and for births to Korean mothers the rate was significantly higher (2.7 per 1000, P=.003). For infants of Chinese mothers, observed risk factors explain the differences observed in unadjusted data. For infants of Cambodian, Japanese, Korean, and Thai mothers, differences persist or widen after risk factors are considered. After risk adjustment, infants of Cambodian, Japanese, and Korean mothers have significantly lower neonatal mortality rates compared with infants born to non-Hispanic white mothers (adjusted odds ratios, 0.58 for infants of Cambodian mothers, 0.67 for infants of Japanese mothers, and 0.69 for infants of Korean mothers; all P<.05); infants of Thai mothers have higher neonatal mortality rates (adjusted odds ratio, 1.89; P<.05).

CONCLUSIONS

There are significant variations in neonatal mortality between subgroups of the Asian American population that are not entirely explained by differences in observable risk factors. Efforts to improve clinical care that treat Asian Americans as a homogeneous group may miss important opportunities for improving infant health in specific subgroups.

Increased Risks of Term Low-Birth-Weight Infants in a Petrochemical Industrial City with High Air Pollution Levels

This study investigated the influence of petrochemical air pollution on birth weight. Birth data on 92,288 singleton infants with gestational periods of 37-44 wk born in a petrochemical industrial city (Kaohsiung, n = 31,530) with severe pollution or a nonpetrochemical industrial city (Taipei, n = 60,758) in Taiwan between 1995 and 1997 were included in this analysis. Air pollutant concentration derived from routinely monitored data showed significantly higher concentrations of SO2, O3, and PM10 in Kaohsiung. Infants with low birth weight (LBW) were significantly more prevalent in Kaohsiung (2.4%) than in Taipei (2.1%). Multivariable logistic regression analysis with adjustment for gestation age, gender, birth order, season of birth, maternal age, and maternal education further suggested that LBW risk in Kaohsiung was 13% higher than that in Taipei (odds ratio [OR] = 1.13, 95%, confidence interval [CI] = 1.03-1.24).

Determinants of intrapartum fetal death in a remote and indigent population in China

OBJECTIVE

To explore the reasons for the high rate of intrapartum fetal death observed in a remote and indigent population in China.

STUDY DESIGN

We conducted an epidemiologic analysis of determinants of intrapartum fetal death in a sample of 20,891 births in 18 hospitals participating in the Qingyuan Perinatal Surveillance System from January 1, 1997 to June 30, 1998. The main determinant examined was cesarean delivery; other determinants included mother's insurance status, residence, maternal age, infant's gender, parity, gestational age, birth weight, and obstetric complications. Rates of intrapartum fetal death within categories of various maternal and infant factors were first calculated and compared; adjusted odds ratios for intrapartum fetal death were then estimated by multiple logistic regression analysis.

RESULTS

The intrapartum fetal death rate in this population was 5 per 1000 total births, which accounted for about one-third of all fetal deaths. Compared with vaginal delivery, elective cesarean delivery was associated with a 100% (i.e., no intrapartum fetal death among 1572 elective cesarean deliveries) and emergency cesarean delivery with a 88% reduction, in intrapartum fetal death. Other significant determinants were related to access to obstetric care (i.e., insurance status and residence).

CONCLUSION

Lack of access to quality obstetric care is the major determinant of intrapartum fetal death in this population.

A comparison of perinatal mortality between ethnic Chinese and ethnic whites: why the Chinese rate was lower

OBJECTIVES

To confirm the observation that has been occasionally reported in the literature that perinatal mortality rate is lower in ethnic Chinese than in ethnic whites, and to assess the reasons for this lower perinatal mortality rate.

METHODS

Secondary-analysis based on published data.

RESULTS

This exercise demonstrates that the perinatal mortality rate was lower in ethnic Chinese than in ethnic whites. The birth weight distribution in ethnic Chinese was more favourable with reduced births at two extremes of the distribution, and the exposure to risk factors for perinatal death by their mothers was also lower.

CONCLUSION

Perinatal mortality rate is lower in ethnic Chinese than in ethnic whites, and the lower perinatal mortality rate in ethnic Chinese is probably caused by their favourable birth weight distribution and lower exposure to risk factors of perinatal death by their mothers.

The influence of fetal and maternal factors on the distribution of birthweight

This review of common risk factors for low birthweight emphasizes the usefulness of examining the entire distribution of birthweight. Of the factors we examined, only short gestational age seemed to affect the low end of the birthweight distribution in the form of skewness. Most factors, such as maternal race, infant sex, plurality, altitude, education, and smoking seem to affect the entire birthweight distribution, indicating a generalized effect. With the exceptions of race, infant sex, parity, and altitude, these factors seemed to have similar associations with both low birthweight and infant mortality. However, only the effects of race and sex on mortality have been repeatedly studied in detail for different combinations of gestational age and birthweight. A few of the factors examined, notably infant sex and parity, have opposite associations with birthweight and infant mortality. Female infants and firstborn infants have lower birthweights than their counterparts, but are more likely to survive. For factors that significantly affect the birthweight distribution, but do not affect mortality equally across the birthweight distribution, the development and use of population-based standards may result in less misclassification of IUGR. Separate standards by infant sex, altitude, and perhaps race may lead to more accurate classification of intrauterine growth. Last, the majority of risk factors have differential effects on birthweight depending on the level of the associated factors. For example, low maternal age and low prepregnancy BMI are associated with both increased risk of low birthweight and poor infant survival. Older maternal age and high prepregnancy BMI are associated with reduced risk of low birthweight, but with increased risk of infant mortality. One possible explanation is that young maternal age and low prepregnancy BMI are associated with adverse behavioral risk factors such as cigarette smoking, whereas increased age and high prepregnancy BMI are associated with gestational diabetes, multiparity, and genetic defects. It is possible that the greater variation in birthweight at the high end of the scale is indicative of increased risk of mortality. Thus, higher birthweight does not always equal better birth outcomes.

Birthweight differentials among Asian Americans

OBJECTIVES

This study examines differentials in mean birthweight and the risk for low birthweight among various Asian-American groups in New York State (n = 499,377).

METHODS

Using resident singleton live-birth records from New York State for 1985 and 1986, Asian-American births were compared with Black, American Indian, and White births. Multivariate ordinary least squares and logistic regression models were used to analyze ethnic differences.

RESULTS

Compared with White births, the expected mean difference in birthweight was -115 g for Chinese, -235 g for Japanese, -164 g for Filipinos, -120 g for Blacks, and 74 g for American Indians. The risk for low birthweight was 45% higher for Filipinos and 49% higher for Blacks as compared with Whites.

CONCLUSIONS

Results of this study suggest substantial heterogeneity in mean birthweight and risk for low birthweight among ethnic groups in general and the major Asian-American groups in particular. Interestingly, after controlling for ethnic differences in sociodemographic risk factors, Filipinos appear to resemble Blacks much more closely than they do their Japanese and Chinese counterparts with respect to risk for low birthweight.

Association of rotating shiftwork with preterm births and low birth weight among never smoking women textile workers in China

1035 married women workers in three modern textile mills in Anhui, China were surveyed to investigate the association of rotating shiftwork with low birth weight and preterm birth in 1992. Information on reproductive health, occupational exposure history, and other covariates including age at pregnancy, time and duration of leave from job since pregnancy, and mill location was obtained by trained nurses with a standardised questionnaire. This analysis was limited to 845 women (887 live births), who were middle or high school graduates, never smokers, and non-alcohol drinkers. About 72% of the women worked an eight day cycle with shift changes every two days throughout pregnancy. Mean gestational age was 38.8 and 39.0 weeks for shift and regular schedule workers, respectively. Multiple linear regression was used to adjust for confounding factors including maternal age at pregnancy, order of live birth, mill location, job title, occupational exposure to dust/gases/fumes, stress, carrying and lifting of heavy loads, working in a squat position, time and duration of leave from the job since pregnancy, and indoor coal combustion for heating. The adjusted difference in gestational age associated with rotating shifts was statistically significant (beta = -0.44 (SE 0.20) weeks.) Mean birth weights were 3248 g and 3338 g for rotating shift workers and regular schedule workers respectively. The estimated effect of rotating shiftwork on birth weight was -79 (SE 42) g. When the analysis was restricted to first order live births or to production workers, the estimated effects of rotating shiftwork on both gestational age and birth weight were significant. The proportions of preterm birth (<37 weeks) and low birth weight (<2500 g), respectively, were 20% and 9% for shift workers and 15% and 6% for regular schedule workers. The adjusted odds ratio of shiftwork was 2.0 (95% CI) 1.1-3.4) for preterm birth and 2.1 (95% CI 1.1-4.1) for low birth weight. This association remained significant when the analysis was restricted to production workers or first order live births.