The contribution of maternal working conditions to socio-economic inequalities in birth outcome

The aims of this study were to examine the association between maternal working conditions and birth outcomes, and to determine the extent to which these contributed to class inequalities in six birth outcomes. We used an existing job exposure matrix developed from survey data collected in 1977 and 1979 to apply occupational-level information on working conditions to the national Swedish Registry, including approximately 280,000 mothers and 360,000 births during the period 1980--1985. Data were analysed using multivariate logistic regressions. Low levels of job control, high levels of physical demands and job hazards were more common in manual compared to non-manual classes. The self-employed had intermediate levels of such exposures. Job exposures, particularly low levels of job control, were generally and significantly associated with higher risks for low birthweight, very low birthweight, small for gestational age, all preterm, very preterm and extremely preterm births, but not with mortality. Compared to middle non-manuals (the reference group), lower non-manual and manual classes had higher risks for all birth outcomes, and these risks were nearly all significant. The highest odds ratios were found for skilled and unskilled manual workers in the manufacturing sector, with ratios between 1.35 and 2.66 (all significant). Job control explained a considerable proportion of inequalities in all birth outcomes. Job hazards contributed particularly to very low birthweight and extremely preterm birth, and physical demands to low birthweight and all preterm births. In conclusion, class differences in maternal working conditions clearly contributed to class differences in low birthweight (explained fraction 14-38%), all preterm births (20-46%), very (14-46%) and extremely (12-100%) preterm births. For very low birthweight and small for gestational age, there was a similar contribution in the manufacturing sector only. For all birth outcomes, class differences could still be detected after working conditions were taken into consideration.     

Cumulative social class and mortality from various causes of adult men

STUDY OBJECTIVE: It is possible that circumstances over the lifecourse contribute to social inequalities in mortality in adulthood. The aim of this study is to assess the cumulative effect of social class at childhood and adulthood on mortality from various causes of death in young adult men. DESIGN: The data consist of census records for all Finnish men born in 1956-60 (112,735 persons and 895,001 person years), and death records (1834 deaths) by cause of death for 1991-98. MAIN RESULTS: Mortality from each cause of death increased from the stable non-manual group to mobile groups, and further to the stable manual group. However, mortality in the downwardly mobile group was 150% higher than in the upwardly mobile group. Furthermore, analyses show that mortality was mainly related to current adult social class, though, within each adult social class men with a manual parental background showed slightly increased mortality from cardiovascular disease and from alcohol related causes. CONCLUSIONS: In these data the effects of adult social class were stronger than childhood class for all causes of death. It is more useful to differentiate between childhood and adulthood effects than to use a combined measure of social class to assess the contribution of social class at different stages of life on mortality.     

Does intergenerational social mobility among men affect cardiovascular mortality? A population-based register study from Sweden

BACKGROUND: Socioeconomic inequalities in cardiovascular mortality are well documented. The aim here is to examine the relation between childhood and adulthood class as well as the role of unique intergenerational social mobility trajectories in such mortality. METHODS: Data were obtained from Swedish registries. Childhood and adulthood information were from the 1960 and 1990 censuses. Men born 1945-59 (809,199) were followed-up for four cardiovascular mortality outcomes 1990- 2002 (5533 deaths) by means of Cox regressions. Three different approaches were applied to study mobility between four main classes. RESULTS: In mutually adjusted models, the effect of a manual adulthood class (compared with non-manuals) was clearly larger (hazard ratios (HR) were 1.56 for MI, 1.70 for stroke, 1.64 for other cardiovascular disease (CVD), 1.62 for all CVD) as for a manual childhood class (1.38, 1.17, 1.24 and 1.28, respectively). This also applied to unclassifiable, while there were few systematic findings for self-employed. When adjusting for education level, childhood class was still significant for MI, other and all CVD, but adulthood class was significant for all outcomes. Trajectory-specific analyses revealed that mobile men from non-manual to manual had significantly higher mortality than mobile from manual to non-manual and stable non-manuals, but not significantly lower than stable manuals. CONCLUSIONS: Cardiovascular mortality was clearly structured by adulthood class, but not as consistently structured by childhood class. The mediating role of education suggests that a major part of life-course disadvantages or advantages in relation to CVD was due to achieved education.     

Risk factors for infant mortality from diseases in Japan 1995-98

OBJECTIVE: Since 1995, additional information (i.e. birth weight, singleton/multiple births, gestational weeks, maternal age, maternal parity and stillbirth experience) has been required for certificates of infant (less than 1 year of age) death from diseases in Japan. The present study examined the effects of biological, demographic and social variables, as reported on birth and death certificates, on infant, neonatal and postneonatal mortality in Japan. METHODS: Using data from vital statistics between 1995 and 1998, more than 4,787,000 livebirths and 16,000 infant deaths from diseases were analyzed. Univariate and multivariate analyses with the Poisson regression model were employed to assess the effects of variables on infant, neonatal and postneonatal mortality by singleton and multiple livebirths separately. RESULTS: The infant mortality rates from diseases were 3.2/1000 for singleton livebirths and 17.7/1000 for multiple livebirths. In singleton livebirths, low birth weight, infant born in earlier years, being a male infant, employment status as "unemployed or unknown", short gestational weeks, late birth in multiparity and maternal stillbirth experience were all significantly related to increased risk of neonatal and postneonatal deaths. Teenage mother were also at high risk of postneonatal deaths. Regional differences were observed. Compared with singleton livebirths, birthweight-specific mortality rates in multiple livebirths were relatively low among infants weighing under 2500 g. In multiple livebirths, elevated risk of death was associated with low birth weight, infant born in earlier years, employment status as "unemployed or unknown" and short gestational weeks. However, late birth in multiparity was related to a reduced risk of death, and maternal stillbirth experience was not a significant variable. CONCLUSION: This study provided the first quantitative estimate of risk of infant mortality from diseases in Japan. Since a more detailed elucidation of actual conditions and risk factors of infant deaths by vital statistics has become possible, efficient measures for improvement of infant mortality are to be expected.     

The postponement of neonatal deaths into the postneonatal period: evidence from Massachusetts

Part of the slow decline in the postneonatal mortality rate and the rapid decline in the neonatal mortality rate during the 1970s may have been due to a postponement of some neonatal deaths into the postneonatal period. The authors hypothesized that any such postponement should be accompanied by a lack of decline, or even an increase, in late neonatal and postneonatal mortality rates among low birth weight babies and babies dying of conditions originating in the perinatal period. To examine this theory, the authors used vital records data to compare infant mortality rates in Massachusetts during 1970-1972 with rates during 1978-1980. Log-linear hazard models were used to calculate death rates, while controlling for changes in maternal age, race, education, and prior reproductive history. The authors found that babies of birth weight under 1,500 g had no decline in late neonatal mortality rates and babies of birth weight under 2,500 g had no decline in postneonatal mortality rates. Babies of birth weight 500-999 g had an increased postneonatal mortality rate (rate ratio = 2.4; 95% confidence limits = 1.0-5.4). These unimproved or increased death rates were due in part to conditions originating in the perinatal period. The authors conclude that, although infant mortality rates have declined, this postponement was real, and that efforts to monitor infant mortality will benefit from its routine quantification.     

Social inequalities in low birth weight in England and Wales: trends and implications for future population health

STUDY OBJECTIVE: To examine social inequalities and trends in low birth weight in England and Wales. DESIGN: Analysis of routine birth data, comparing (a) couple and sole registered births, and (b) manual and non-manual occupational groups. SETTING: England and Wales, 1993-2000. MAIN RESULTS: Social inequalities in low birth weight were evident throughout 1993-2000: relative to the non-manual group, there is an increased risk for the manual group (range in RR 1.22-1.35) and sole registrations (RR 1.51-1.67). An estimated 6.5% (2979 births) of low birth weight in 2000 could have been avoided if risks associated with the manual group were absent, and 2.8% (1290 births) avoided if risks associated with sole registration were absent. Between 1993 and 2000, the low birthweight rate increased significantly with an estimated overall increase of 11%. Increases were evident in all social groups (15% in manual, 11% in sole registrations and 9% in non-manual); however relative to non-manual the increase in RRs were not statistically significant for manual or sole registrations. When multiple births are excluded, the rate of low birth weight is reduced but there is still a significant increase over time and social differentials are undiminished. CONCLUSIONS: There are social inequalities in low birth weight in England and Wales that have not narrowed over an eight year period, 1993-2000. These inequalities are likely to affect childhood and adult health inequalities in the future, hence strategies will need to address differences in low birth weight and further monitoring of trends is therefore desirable.     

Intergenerational class mobility and cardiovascular mortality among Swedish women: A population-based register study

Class inequalities in cardiovascular disease (CVD) mortality are well documented, but the impact of intergenerational class mobility on CVD mortality among women has not been studied thoroughly. We examined whether women's mobility trajectories might contribute to CVD mortality beyond what could be expected from their childhood and adult social class position. The Swedish Work and Mortality Data Base provided childhood (1960) and adulthood (1990) social indicators. Women born 1945–59 (N = 791?846) were followed up for CVD mortality 1990–2002 (2019 deaths) by means of logistic regression analysis. CVD mortality risks were estimated for 16 mobility trajectories. Gross and net impact of four childhood and four adult classes, based on occupation, were analysed for mortality in ischemic heart disease (IHD), stroke, other CVD, – and all CVD. Differences between the two most extreme trajectories were 10-fold, but the common trajectory of moving from manual to non-manual position was linked to only a slight excess mortality (OR = 1.26) compared to the equally common trajectory of maintaining a stable non-manual position (reference category). Moving into adult manual class resulted in an elevated CVD mortality whatever the childhood position (ORs varied between 1.42 and 2.24). After adjustment for adult class, childhood class had some effect, in particular there was a low risk of coming from a self-employed childhood class on all outcomes (all ORs around = 0.80). A woman's own education had a stronger influence on the mortality estimates than did household income. Social mobility trajectories among Swedish women are linked to their CVD mortality risk. Educational achievement seems to be a key factor for intergenerational continuity and discontinuity in class-related risk of CVD mortality among Swedish women. However, on mutual adjustment, adult class was much more closely related to CVD mortality than was class in childhood.     

Familial risk of premature cardiovascular mortality and the impact of intergenerational occupational class mobility

The negative impact of low social class on cardiovascular disease (CVD) and mortality has been consistently documented. However, less scientific consistency exists in terms of whether a unique health effect of social mobility from childhood to adulthood prevails. This study explored how childhood and adult social class and the transition between them (social mobility), are related to premature CVD mortality when familial aggregation of CVD among siblings is also considered. The study includes nearly 1.9 million Swedish residents born 1939-1959 distributed over 1,044,725 families, of whom 14,667 died prematurely from CVD in 1990-2003. Information on parental class (1960) and own mid-life occupational class (1990) was retrieved from the respective censuses. Odds ratios for premature CVD mortality according to trajectory-specific social mobility, along with pairwise mean odds ratios for sibling resemblance of premature CVD mortality, were calculated by means of alternating logistic regression. This model calculates the remaining dependency of CVD mortality within sibships after accounting for available risk factors (like parental and adult social class) in the population mean model. Results showed that premature CVD mortality was associated with both parental and own adult social class. A clear tendency for the downwardly mobile to have increased, and for the upwardly mobile to experience a decreased risk of premature CVD mortality was found, as well as a corresponding unique effect of social mobility per se among the manual and non-manual classes. This effect was verified for men, but not for women, when they were analysed separately. The pairwise mean odds ratios for premature CVD mortality among full siblings were 1.78 (95% CI: 1.52-2.08), and were independent of parental CVD mortality and parental or adult occupational class.     

Postneonatal mortality in Alabama: why no progress in the 90s?

PURPOSE: To examine the factors associated with postneonatal mortality. METHODS: Logistic regression was used to examine the effects of various variables on postneonatal mortality in Alabama. RESULTS: The most important predictor of postneonatal mortality was birth weight. Social and economic variables were also important in explaining postneonatal mortality. CONCLUSIONS: Reductions in postneonatal mortality may require closer case management of low birth weight neonatal survivors. Survival of these infants creates a cohort at risk of postneonatal mortality. Many of these low birth weight infants are born into an environment where their mothers' parenting potential is compromised by youth and poverty. This may be responsible for the failure to reduce postneonatal mortality and explain its increasing proportion of infant deaths; deaths may be being postponed from the neonatal to the postneonatal period.     

Social mobility, marital status, and mortality risk in an adult life course perspective: the Malmö Preventive Project

AIMS: Adverse social factors predict increased mortality. This study aimed to assess the influence of social class and marital status on mortality, adding an adult life course perspective. METHODS: In total, 32,907 males and 20,204 females were evaluated based on census data in Malm?, Sweden. Of these subjects, 22,444 males and 10,902 females also took part in health screening. The main outcomes were all-cause and cause-specific mortality rates in subgroups based on social class and marital status, either measured once or repeatedly in adult life. Results were based on a total of 522,807 years of follow-up in men (5,761 deaths) and 239,815 in women (1,354 deaths). RESULTS: Total and cardiovascular mortality were significantly higher in manual male employees with age-adjusted risk ratios (RR) of 1.7 (95% CI 1.5-1.9) and 1.6 (1.3-2.0) in skilled manual workers, and 2.0 (1.7-2.2) and 1.9 (1.6-2.3) in unskilled manual workers, compared with high-level non-manual employees. The differences remained after adjustment for baseline risk factors and prevalent cardiovascular disease, and were similar for women. Increased mortality risk was also documented for subjects who were divorced or unmarried (adjusted for social class), as well as being downward socially mobile or in a permanent low social class (manual) position. CONCLUSIONS: Social class based on occupation, either measured once or repeatedly in adult life, is associated with marked differences in mortality risk in middle-aged subjects. People who remain married/cohabiting or remarry are at lower risk of early death than people who remain unmarried or divorced.     

Accuracy of adults' recall of childhood social class: findings from the Aberdeen children of the 1950s study

BACKGROUND: Although adult reported childhood socioeconomic position has been related to health outcomes in many studies, little is known about the validity of such distantly recalled information. This study evaluated the validity of adults' reports of childhood paternal social class. METHODS: Data are drawn from the Aberdeen children of the 1950s study, a cohort of 12 150 people born in Aberdeen (Scotland) who took part in a school based survey in 1962. In this survey, two indices of early life socioeconomic position were collected: occupational social class at birth (abstracted from maternity records) and occupational social class in childhood (reported during the 1962 survey by the study participants). Between 2000 and 2003, a questionnaire was mailed to traced middle aged cohort members in which inquiries were made about their fathers' occupation when they were aged 12 years. The level of agreement between these reports and prospectively collected data on occupational social class was assessed. RESULTS: In total, 7183 (63.7%) persons responded to the mid-life questionnaire. Agreement was moderate between social class of father recalled in adulthood and that measured in early life (kappa statistics were 0.47 for social class measured at birth, and 0.56 for social class reported by the child). The relation of occupational social class to birth weight and childhood intelligence was in the expected directions, although weaker for adults' reports in comparison with prospectively gathered data. CONCLUSIONS: In studies of adult disease aetiology, associations between childhood social class based on adult recall of parental occupation and health outcomes are likely to underestimate real effects.     

The Effect of an Increased Minimum Wage on Infant Mortality and Birth Weight

Objectives. To investigate the effects of state minimum wage laws on low birth weight and infant mortality in the United States.Methods. We estimated the effects of state-level minimum wage laws using a difference-in-differences approach on rates of low birth weight (< 2500 g) and postneonatal mortality (28–364 days) by state and month from 1980 through 2011. All models included state and year fixed effects as well as state-specific covariates.Results. Across all models, a dollar increase in the minimum wage above the federal level was associated with a 1% to 2% decrease in low birth weight births and a 4% decrease in postneonatal mortality.Conclusions. If all states in 2014 had increased their minimum wages by 1 dollar, there would likely have been 2790 fewer low birth weight births and 518 fewer postneonatal deaths for the year.Previous research has consistently linked low income with increased risk of premature mortality throughout the life span.1,2 As a stark example, the US excess infant mortality rate (defined in comparison with 4 peer countries) during the postneonatal period (28–364 days) is driven almost entirely by excess infant deaths among mothers of lower socioeconomic status.3 Low birth weight is also a sensitive consequence of low income, has been established as one of the most important predictors of infant mortality, and increases the risk of deleterious health and economic effects into adulthood.4 Alarmingly, more than 1 in 4 women giving birth in the United States are below poverty level.5Minimum wage standards are an important potential contributor to family economic security and, therefore, may influence maternal and infant health outcomes. Women, those with low educational attainment, young workers, and those in the service industry are more likely to be paid the federal minimum wage or less.6 At present, minimum wage laws are prominent on the public agenda, being debated at city, state, and federal levels as a strategy to reduce growing income inequality and poverty. Economists have described the minimum wage as one of the most studied topics and have long examined potential deleterious market effects related to legislated increases in minimum wage. A recent review found no significant employment loss from modest increases in minimum wage,7 although scientific debate continues. It is important to note that the current federal minimum wage ($15 080 annual income) is not sufficient to lift a full-time worker with 1 or 2 children above the poverty threshold ($15 930 and $20 090, respectively).Despite the established link between low income and ill health, few studies have examined how minimum wage policies affect health outcomes.8,9 We have taken advantage of natural experiments in minimum wage laws across states and time over the past 30 or more years to empirically evaluate the hypothesis that increases in state-level minimum wages are associated with reduced rates of low birth weight infants and infant mortality.10     

Variation in state-specific infant mortality risks

Data from the National Infant Mortality Surveillance project were used to examine the State-specific variations in infant, neonatal, and postneonatal mortality and to examine some of the factors affecting the risks of death. The infant mortality risk, defined as the risk of death before 1 year of age to an infant born in the 1980 birth cohort, in the highest risk State was nearly three times that in the lowest risk State. Mortality risk ratios of two or greater were found when comparing high and low States for overall black infant mortality risks, overall neonatal mortality, neonatal mortality risks for black and white infants examined separately, neonatal mortality risks for low birth weight infants regardless of race, and overall postneonatal mortality and postneonatal mortality for white infants. The lowest State-specific black mortality risks were higher than the highest white risks for overall infant mortality and neonatal mortality. The differences between State extremes in mortality risks are greater than the differences between the United States and the Scandinavian countries with the lowest infant mortality.     

Degree of rural isolation and birth outcomes

Little is known about how birth outcomes vary in rural areas by degree of rural isolation. We conducted a retrospective cohort study of all births in Quebec, 1991-2000 to assess birth outcomes by the degree of rural isolation according to metropolitan influence as measured by work force commuting flows between rural and urban areas. Compared with urban areas, crude risks of preterm birth, small-for-gestational age birth, stillbirth, neonatal death and postneonatal death were similar in rural areas with strong metropolitan influence, but were significantly higher for preterm birth, stillbirth and postneonatal death in rural areas with weak or no metropolitan influence, and for neonatal death in rural areas with no metropolitan influence. Adjustment for maternal characteristics (age, mother tongue, education, marital status, parity, plurality and infant sex) attenuated the associations. The adjusted odds ratios [95% confidence intervals] were 1.36 [1.12, 1.64] for stillbirth in rural areas with weak metropolitan influence, 1.63 [1.14, 2.32] for neonatal death in rural areas with no metropolitan influence, 1.78 [1.21, 2.63] and 1.37 [1.07, 1.75] for postneonatal death in rural areas with weak and no metropolitan influence, respectively. Much higher neonatal death rates were observed for preterm or low-birthweight babies in rural areas with no metropolitan influence, suggesting inadequate access to optimal neonatal care. We conclude that birth outcomes in rural areas differ according to the degree of rural isolation. Fetuses and infants of mothers from rural areas with weak or no metropolitan influence are particularly vulnerable to the risks of death during the perinatal and postnatal periods.     

Association of childhood socioeconomic position with cause-specific mortality in a prospective record linkage study of 1,839,384 individuals

Previous studies have lacked sufficient power to assess associations between early-life socioeconomic position and adult cause-specific mortality. The authors examined associations of parental social class at age 0-16 years with mortality among 1,824,064 Swedes born in 1944-1960. Females and males from manual compared with nonmanual childhood social classes were more likely to die from smoking-related cancers, stomach cancer, respiratory disease, cardiovascular disease, and diabetes. Males from manual compared with nonmanual social classes were more likely to die from unintentional injury, homicide, and alcoholic cirrhosis. The association with stomach cancer was little affected by adjustment for parental later-life and own adult social class or education. For other outcomes, educational attainment resulted in greater attenuation of associations than did adjustment for adult social class. Early-life social class was not related to suicide or to melanoma, colon, breast, brain, or lymphatic cancers or to leukemia. With the exception of stomach cancer, caused by Helicobacter pylori infection acquired in childhood, poorer social class in early life was associated with diseases largely caused by behavioral risk factors such as smoking, physical inactivity, and an unhealthy diet. Educational attainment may be important in reducing the health inequalities associated with early-life disadvantage.     

Maternal Early Life Risk Factors for Offspring Birth Weight: Findings from the Add Health Study

The aim of this study was to examine the pathways that link mothers’ early life socio economic status (SES) and mothers’ experience of childhood maltreatment with birth weight among their later born offspring. Data were drawn from a nationally representative longitudinal survey of school-aged respondents, initially enrolled during adolescence in Wave I (1994–1995) and Wave II (1996) of the National Longitudinal Study of Adolescent Health and followed-up in adulthood in Wave III (2001–2002). Data on offspring birth weight were obtained from nulliparous females (N = 1,897) who had given birth between Waves II and III. Analyses used structural equation modeling to examine the extent to which early life maternal risk predicted offspring birth weight, and demonstrated that maternal childhood SES and maternal childhood maltreatment predicted offspring birth weight through several mediated pathways. First, maternal adolescent substance use and prenatal cigarette use partially mediated the association between maternal childhood SES and offspring birth weight. Second, maternal adolescent depressive symptoms and adult SES partially mediated the association between maternal childhood SES and offspring birth weight. Third, adult SES partially mediated the association between maternal childhood SES and offspring birth weight. Fourth, maternal adolescent substance use and prenatal cigarette use partially mediated the association between maternal childhood maltreatment and offspring birth weight. Finally, maternal adolescent depressive symptoms and adult SES partially mediated the association between maternal childhood maltreatment and offspring birth weight. To our knowledge, this is the first study to identify maternal childhood maltreatment as an early life risk factor for offspring birth weight among a nationally representative sample of young women, and to demonstrate the mechanisms that link childhood SES and maltreatment to offspring birth weight. These findings suggest the importance of designing and implementing prevention and intervention strategies to address early life maternal social conditions in an effort to improve inter generational child health at birth.     

Overview of the National Infant Mortality Surveillance (NIMS) project--design, methods, results

The recent slowdown in the decline of infant mortality in the United States and the continued high risk of death among black infants (twice that of white infants) prompted a consortium of Public Health Service agencies to collaborate with all States in the development of a national data base from linked birth and infant death certificates. This National Infant Mortality Surveillance (NIMS) project for the 1980 U.S. birth cohort provides neonatal, postneonatal, and infant mortality risks for blacks, whites, and all races in 12 categories of birth weights. (Note: Neonatal mortality risk = number of deaths to infants less than 28 days of life per 1,000 live births; postneonatal mortality risk = number of deaths to infants 28 days to less than 1 year of life per 1,000 neonatal survivors; and infant mortality risk = number of deaths to infants less than 1 year of life per 1,000 live births.) Separate tabulations were requested for infants born in single and multiple deliveries. For single-delivery births, tabulations included birth weight, age at death, race of infant, and each of these characteristics: infant's live-birth order, sex, gestation, type of delivery, and cause of death; and mother's age, education, prenatal care history, and number of prior fetal losses at 20 weeks' or more gestation. An estimated 95 percent of eligible deaths were included in the NIMS tabulations. The analyses focus on three components of infant mortality: birth weight distribution of live births, neonatal mortality, and postneonatal mortality. The most important predictor for infant survival was birth weight, with an exponential improvement in survival by increasing birth weight to its optimum level. The nearly twofold higher risk of infant mortality among blacks was related to a higher prevalence of low birth weights and to higher mortality risks in the neonatal period for infants weighing 3,000 grams or more, and in the postneonatal period for all infants, regardless of birth weight. Regardless of other infant or maternal risk factors, the black-white gap persisted for infants weighing 2,500 grams or more.     

Early environment and child-to-adult growth trajectories in the 1958 British birth cohort

BACKGROUND: Genetics and environmental conditions early in life are known to influence height. However, evidence is restricted to studies conducted at a specific age, and thus the effect on the entire growth trajectory has been neglected. OBJECTIVE: The objective was to determine when parental height and factors early in offspring life start to affect offspring height, when these variables have the strongest effect, and whether these variables persist to adulthood. DESIGN: Longitudinal data from the 1958 British birth cohort (all of whom were born during 1 wk in March 1958), including height measurements at 7, 11, 16, and 33 y of age, were analyzed by using multivariate multilevel response models. RESULTS: Parental height, birth weight, maternal smoking during pregnancy, breastfeeding, parental divorce, and socioeconomic factors were all significantly associated with childhood height, but their effects differed thereafter. Parental height and birth weight were most strongly associated with offspring height, and their effects persisted (adjusted increase in adult height: 2 cm for 1 SD of maternal or paternal height, or 1 kg of birth weight). Socioeconomic disadvantage (manual social class, large family size, and overcrowded households) was associated with substantial deficits of 2-3 cm (adjusted estimates) in height at 7 y. Catch-up growth was apparent but was insufficient to overcome the initial insult on growth; the adjusted deficit was as high as 1 cm in adulthood. CONCLUSIONS: Children from disadvantaged backgrounds have a delayed pattern of growth before the pubertal spurt, which is followed by catch-up growth. The health consequences of this pattern of growth need to be examined in future studies.     

Birth order and mortality: a life-long follow-up of 14,200 boys and girls born in early 20th century Sweden

The present study examines the sex-specific patterns of mortality by birth order in four stages of the life-course, using Poisson and logistic regression analysis. The main question posed is whether there is any continuing social effect of birth order when (a) biological factors at birth, (b) other social factors at birth and (c) socio-economic circumstances in adulthood are adjusted for. The analyses are based on the Uppsala Birth Cohort Study consisting of all 14,192 boys and girls who were born alive at the Uppsala Academic Hospital in Sweden during the period 1915-9. The results showed that all-cause mortality differed according to birth order in all of the four studied age intervals when birth year, mother's age, birth weight, gestational age, diseases of mother, diseases of the infant, social class and mother's marital status at the time of childbirth were adjusted for. The general tendency was for laterborn siblings, particularly girls women, to demonstrate a higher mortality risk than firstborn children. However, in the oldest age group (55-80 years) the previously significant association between birth order and male mortality became insignificant when adult socio-economic circumstances were controlled for. This indicates that the long-term influence of childhood birth order position on mortality is partly mediated by adult social class, education and income. The concluding section of the paper notes that laterborn children, and especially girls, were a disadvantaged group in early 20th century Sweden. Thus, for the subjects in the present study, the childhood social conditions linked to birth order position seem to have had consequences for these individuals' health and survival that extend over the whole life-course.     

Early-life origins of adult disease: national longitudinal population-based study of the United States

Objectives. We examined the relation between low birth weight and childhood family and neighborhood socioeconomic disadvantage and disease onset in adulthood.Methods. Using US nationally representative longitudinal data, we estimated hazard models of the onset of asthma, hypertension, diabetes, and stroke, heart attack, or heart disease. The sample contained 4387 children who were members of the Panel Study of Income Dynamics in 1968; they were followed up to 2007, when they were aged 39 to 56 years. Our research design included sibling comparisons of disease onset among siblings with different birth weights.Results. The odds ratios of having asthma, hypertension, diabetes, and stroke, heart attack, or heart disease by age 50 years for low–birth weight babies vs others were 1.64 (P < .01), 1.51 (P < .01), 2.09 (P < .01), and 2.16 (P < .01), respectively. Adult disease prevalence differed substantially by childhood socioeconomic status (SES). After accounting for childhood socioeconomic factors, we found a substantial hazard ratio of disease onset associated with low birth weight, which persisted for sibling comparisons.Conclusions. Childhood SES is strongly associated with the onset of chronic disease in adulthood. Low birth weight plays an important role in disease onset; this relation persists after an array of childhood socioeconomic factors is accounted for.The fetal origins hypothesis, developed by David Barker,¹ proposes that when nutritional intake of a fetus is limited, the body''s physiology and metabolism are changed fundamentally, and some of the consequences of these changes become apparent much later in life. Health insults in utero may lead to greater physiological deterioration of metabolic and immune systems. Early-life health may influence a broad range of subsequent disease risks over the life cycle. Over the past 2 decades, a voluminous empirical literature has documented associations between early-life health outcomes—most often, but not exclusively, low birth weight—and adult mortality and disease onset.^1–5 The fetal origins hypothesis provides an explanation of why there may be important interactions between parental health status and parental economic status in their children''s subsequent risk of onset of disease in adulthood.At the same time, evidence from human and animal studies highlights the importance of other early-life factors that set in place the structures that shape future health outcomes.⁶ Specifically, limited parental resources and childhood poverty can reduce investments in children''s health and learning, shape the neurobiology of the developing child, and lead to worse health later in life.^7–10 Lack of health insurance for childhood can discourage the use of medical care, particularly in the early and more treatable stages of a health problem. High levels of neighborhood poverty and associated stressors can limit development and lead to poor health, and they can also compound and amplify the neurobiological disadvantages that many poor children already face.¹¹These various factors in early life—health status (e.g., low birth weight may serve as a marker for poor infant health), familial socioeconomic disadvantage, health insurance coverage, and neighborhood disadvantage—are highly correlated in most populations; children living in poor families disproportionately live in poor neighborhoods, lack high-quality health care, and have poor health. As a result, the typically estimated statistical association between birth weight and adult health status may be spurious and instead reflect the lasting influence of hereditary risk factors and childhood family and neighborhood socioeconomic disadvantage, which are correlated with both low birth weight and onset of chronic disease. The evidence to date remains inconclusive in distinguishing between these competing explanations, and there is ongoing debate regarding the source of reported associations between low birth weight and risks of chronic diseases later in life.^12–15 Assessing the relative importance of these competing explanations has implications for our understanding of the early-life origins of adult disease.We examined the long-term consequences of low birth weight and childhood socioeconomic disadvantage on the onset of fatal chronic conditions in adulthood in the United States. We used nationally representative longitudinal data from the United States spanning nearly 4 decades to estimate the onset of chronic health conditions that are among the leading causes of mortality and disability.