Lifetime socioeconomic position and twins' health: an analysis of 308 pairs of United States women twins

The Dynamic Nature of the Socioeconomic Determinants of Cardiovascular Health: A Narrative Review

Despite decades of social epidemiologic research, health inequities remain pervasive and ubiquitous in Canada and elsewhere. One reason may be our use of socioeconomic measurement, which has often relied on single point-in-time exposures. To explore the extent to which researchers have incorporated dynamic socioeconomic measurement into cardiovascular health outcome evaluations, we performed a narrative review. We estimated the prevalence of socioeconomic longitudinal cardiovascular research studies that identified socioeconomic exposures at 2 or more points in time between the years of 2019 and 2023. We defined cardiovascular outcome studies as those that examined coronary artery disease, myocardial infarction, acute coronary syndrome, stroke, heart failure, cardiac arrhythmias, cardiac death, cardiometabolic factors, transient ischemic attacks, peripheral artery disease, or hypertension. Socioeconomic exposures included individual income, neighbourhood income, intergenerational social mobility, education, occupation, insurance status, and economic security. Seven percent of socioeconomic cardiovascular outcome studies have measured socioeconomic status at 2 or more points in time throughout the follow-up period, hypothesized mechanisms by which dynamic socioeconomic measures affected outcome focused on social mobility, accumulation, and critical period theories. Insights, implications, and future directions are discussed, in which we highlight ways in which postal code data can be better used methodologically as a dynamic socioeconomic measure. Future research must incorporate dynamic socioeconomic measurement to better inform root causes, interventions, and health-system designs if health equity is to be improved.

A Review of the Relationship between Socioeconomic Status Change and Health

OBJECTIVES

This review aimed to identify and synthesize the existing literature on the effects of socioeconomic status (SES) changes on health.

METHODS

A review was conducted using Medline, Cochrane library, and CINAHL (Cumulative Index to Nursing and Allied Health Literature). All longitudinal or cross-sectional studies that examined links between changes to SES across different time periods and measured health outcomes were included. Screening was conducted using select inclusion and exclusion criteria in order of title, abstract, and full text. Two independent reviewers assessed the quality of the full text articles using the Downs and Black checklist.

RESULTS

Our literature search led to 2719 peer reviewed articles, 2639 of which were title screened after duplicates were removed. A total of 117 abstracts and 12 full text articles were screened. Overall, findings from 11 articles form the basis of this review. Eight different types of measures of changes to SES were identified. These include education, occupation, economic security, income sufficiency, home ownership, car ownership, health insurance, and marital status. Assessed outcomes included measures related to physical health, cardiovascular disease, mental health, and oral health. A large proportion of studies found that an SES change impacts health. Evidence suggests that those with consistently high SES have the best health outcomes, followed by those who report their SES change from low to high (upward social mobility). Evidence on the relative health effects for those who report their SES change from high to low (downward social mobility) compared to those who report consistently low SES is inconsistent.

CONCLUSION

Current evidence suggests that an SES change has an impact on an individual's health. More research on the effects of SES changes on health outcomes in adulthood is needed and can inform various areas of health research including health resiliency and development. Future studies should focus on individual SES indicators and their effects on health outcomes at multiple points throughout life.

Heritability of Coronary Artery Disease: Insights From a Classical Twin Study

BACKGROUND

Genetics have a strong influence on calcified atherosclerotic plaques; however, data regarding the heritability of noncalcified plaque volume are scarce. We aimed to evaluate genetic versus environmental influences on calcium (coronary artery calcification) score, noncalcified and calcified plaque volumes by coronary computed tomography angiography in adult twin pairs without known coronary artery disease.

METHODS

In the prospective BUDAPEST-GLOBAL (Burden of Atherosclerotic Plaques Study in Twins-Genetic Loci and the Burden of Atherosclerotic Lesions) classical twin study, we analyzed twin pairs without known coronary artery disease. All twins underwent coronary computed tomography angiography to assess coronary atherosclerotic plaque volumes. Structural equation models were used to quantify the contribution of additive genetic, common environmental, and unique environmental components to plaque volumes adjusted for age, gender, or atherosclerotic cardiovascular disease risk estimate and statin use.

RESULTS

We included 196 twins (mean age±SD, 56±9 years, 63.3% females), 120 monozygotic and 76 same-gender dizygotic pairs. Using structural equation models, noncalcified plaque volume was predominantly determined by environmental factors (common environment, 63% [95% CI, 56%-67%], unique environment, 37% [95% CI, 33%-44%]), while coronary artery calcification score and calcified plaque volumes had a relatively strong genetic heritability (additive genetic, 58% [95% CI, 50%-66%]; unique environmental, 42% [95% CI, 34%-50%] and additive genetic, 78% [95% CI, 73%-80%]; unique environmental, 22% [95% CI, 20%-27%]), respectively.

CONCLUSIONS

Noncalcified plaque volume is mainly influenced by shared environmental factors, whereas coronary artery calcification score and calcified plaque volume are more determined by genetics. These findings emphasize the importance of early lifestyle interventions in preventing coronary plaque formation.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01738828.

Lower Socioeconomic Position Is Associated with Greater Activity in and Integration within an Allostatic-Interoceptive Brain Network in Response to Affective Stimuli

Socioeconomic inequities shape physical health and emotional well-being. As such, recent work has examined the neural mechanisms through which socioeconomic position (SEP) may influence health. However, there remain critical gaps in knowledge regarding the relationships between SEP and brain function. These gaps include a lack of research on: (1) the association between SEP and brain functioning in later life, (2) relationships between SEP and functioning of the whole brain beyond specific regions of interest, and (3) how neural responses to positive affective stimuli differ by SEP. The current study addressed these gaps by examining the association between SEP (i.e., education, income) and neural responses to affective stimuli among 122 mid- to late-life adults. During MRI scanning, participants viewed 30 positive, 30 negative, and 30 neutral images; activation and network connectivity analyses explored associations between SEP and neural responses to these affective stimuli. Analyses revealed that those with lower SEP showed greater neural activity to both positive and negative images in regions within the allostatic-interoceptive network, a system of regions implicated in representing and regulating physiological states of the body and the external environment. There were no positive associations between SEP and neural responses to negative or positive images. In addition, graph-theory network analyses showed that individuals with lower SEP demonstrated greater global efficiency within the allostatic-interoceptive network and executive control network, across all task conditions. The findings suggest that lower SEP is associated with enhanced neural sensitivity to affective cues that may be metabolically costly to maintain over time and suggest a mechanism by which SEP might get "under the skull" to influence mental and physical well-being.

Psychopathologies and socioeconomic status as risk indicators for periodontitis: a survey-based investigation in German dental practices

OBJECTIVES

Periodontitis is a highly prevalent multifactorial disease associated with various mental disorders. However, study results about this association are still contradictory. One methodological reason could be the neglect of potential confounders, such as socioeconomic factors or mental comorbidity. Our study examined a wide range of potential psychosocial risk indicators to identify those with relevant associations to periodontitis.

MATERIALS AND METHODS

In a cross-sectional study, 111 patients with periodontitis (PERIO) (> 30% teeth with approximal attachment loss ≥ 5 mm) and 110 patients without periodontitis (NON-PERIO) were recruited in four dental practices in Germany. Clinical attachment loss, pocket depth, plaque, bleeding on probing, and DMFT were measured. Psychopathologic symptoms and socioeconomic status were recorded using self-report questionnaires (DAS, PHQ-8, GAD-7, CTS, SCOFF, AUDIT, FTND, SSS-8, SES).

RESULTS

The PERIO group reported significantly lower socioeconomic status (Cohen's d = 0.49) and higher psychopathological symptom burden than the NON-PERIO regarding dental anxiety (d = 0.86) and avoidance behavior, nicotine dependency (d = 0.84), depressiveness (d = 0.46), general anxiety (d = 0.45), somatic symptoms (d = 0.42), and childhood traumatization (d = 0.34). No significant group differences existed for alcohol abuse and eating disorders. Dental anxiety was the strongest predictor of periodontitis and showed significant correlations with other psychopathologies and social status.

CONCLUSIONS

Out of all psychosocial factors, socioeconomic status and dental anxiety showed the greatest association with periodontitis.

CLINICAL RELEVANCE

Dentists should encourage socially disadvantaged and dentally anxious patients in the utilization of prevention and dental care. Furthermore, physicians and psychotherapists can contribute to the early detection of dental anxiety, oral diseases, and avoidance behavior.

Can I Buy My Health? A Genetically Informed Study of Socioeconomic Status and Health

BACKGROUND

A large literature demonstrates associations between socioeconomic status (SES) and health, including physiological health and well-being. Moreover, gender differences are often observed among measures of both SES and health. However, relationships between SES and health are sometimes questioned given the lack of true experiments, and the potential biological and SES mechanisms explaining gender differences in health are rarely examined simultaneously.

PURPOSE

To use a national sample of twins to investigate lifetime socioeconomic adversity and a measure of physiological dysregulation separately by sex.

METHODS

Using the twin sample in the second wave of the Midlife in the United States survey (MIDUS II), biometric regression analysis was conducted to determine whether the established SES-physiological health association is observed among twins both before and after adjusting for potential familial-level confounds (additive genetic and shared environmental influences that may underly the SES-health link), and whether this association differs among men and women.

RESULTS

Although individuals with less socioeconomic adversity over the lifespan exhibited less physiological dysregulation among this sample of twins, this association only persisted among male twins after adjusting for familial influences.

CONCLUSIONS

Findings from the present study suggest that, particularly for men, links between socioeconomic adversity and health are not spurious or better explained by additive genetic or early shared environmental influences. Furthermore, gender-specific role demands may create differential associations between SES and health.

Explaining socioeconomic disparities in health behaviours: A review of biopsychological pathways involving stress and inflammation

The purpose of this article was to explore how individuals' position in a socioeconomic hierarchy is related to health behaviours that are related to socioeconomic disparities in health. We identified research which shows that: (a) low socioeconomic status (SES) is associated with living in harsh environments, (b) harsh environments are related to increased levels of stress and inflammation, (c) stress and inflammation impact neural systems involved in self-control by sensitising the impulsive system and desensitising the reflective system, (d) the effects are inflated valuations of small immediate rewards and deflated valuations of larger delayed rewards, (e) these effects are observed as increased delay discounting, and (f) delay discounting is positively associated with practicing more unhealthy behaviours. The results are discussed within an adaptive evolutionary framework which lays out how the stress response system, and its interaction with the immune system and brain systems for decision-making and behaviours, provides the biopsychological mechanisms and regulatory shifts that make widespread conditional adaptability possible. Consequences for policy work, interventions, and future research are discussed.

Association of Adult Socioeconomic Status with Body Mass Index: A Within- and Between-Twin Study

Adult socioeconomic status (SES) has been consistently associated with body mass index (BMI), but it is unclear whether it is linked to BMI independently of childhood SES or other potentially confounding factors. Twin studies can address this issue by implicitly controlling for childhood SES and unmeasured confounders. This co-twin control study used cross-sectional data from Twins Research Australia's Health and Lifestyle Questionnaire (N = 1918 twin pairs). We investigated whether adult SES, as measured by both the Index of Relative Socioeconomic Disadvantage (IRSD) and the Australian Socioeconomic Index 2006 (AUSEI06), was associated with BMI after controlling for factors shared by twins within a pair. The primary analysis was a linear mixed-effects model that estimated effects both within and between pairs. Between pairs, a 10-unit increase in AUSEI06 was associated with a 0.29 kg/m2 decrease in BMI (95% CI [-.42, -.17], p < .001), and a 1-decile increase in IRSD was associated with a 0.26 kg/m2 decrease in BMI (95% CI [-.35, -.17], p < .001). No association was observed within pairs. In conclusion, higher adult SES was associated with lower BMI between pairs, but no association was observed within pairs. Thus, the link between adult SES and BMI may be due to confounding factors common to twins within a pair.

Socioeconomic status, well-being and mortality: a comprehensive life course analysis of panel data, Germany, 1984-2016

BACKGROUND

This study seeks to explore potential causal mechanisms involved in the observed associations between several socioeconomic status (SES) indicators, well-being and mortality, by taking a life course perspective focusing on (i) the trajectory of income and domain-specific well-being indicators, (ii) the influence of different SES indicators on well-being and mortality, (iii) the interactions between those trajectories, and (iv) the associations of the income and domain-specific well-being trajectories with all-cause mortality.

METHODS

Socioeconomic status is operationalised by net household income, education, employment and marital status. Well-being is measured with two indicators: life satisfaction and satisfaction with health. Data from the German Socio-Economic Panel, collected between 1984 and 2016 and comprising more than 55,000 individuals, are analysed by means of longitudinal k-means cluster analysis, simultaneous equation systems and parametric time-to-death regressions.

RESULTS

The analyses indicate the presence of large reciprocal effects of the trajectories of income and well-being on each other. However, the results suggest that well-being has a larger influence on income than the opposite, namely, income on well-being. The mortality analysis, on the other hand, revealed that the history of satisfaction with health is a much stronger predictor of longevity than the individual's income history. Mortality risk was found lower among married individuals and those with tertiary education. In contrast, unemployment was associated with lower income and well-being levels. The findings provide support to the notion that education is a superior SES indicator than income in the investigation of the social determinants of well-being and mortality.

CONCLUSION

The present study provides evidence of large reciprocal effects of income and well-being and emphasises the importance of taking a life course approach in the investigation of the social determinants of health. Several SES indicators and both well-being indicators were found to be highly predictive of all-cause mortality and indicate the presence of cumulative effects related to one's income and well-being trajectories.

Association of Parental Socioeconomic Status and Newborn Telomere Length

IMPORTANCE

Low socioeconomic status is associated with higher all-cause mortality and risks for aging-related diseases. Biological aging is a potential process underlying health conditions related to social disadvantages, which may be present from birth onward.

OBJECTIVE

To evaluate the association of parental socioeconomic status with telomere length (TL) at birth, a marker of biological aging.

DESIGN, SETTING, AND PARTICIPANTS

This prospective birth cohort study was conducted among 1504 mother-newborn pairs in Belgium recruited between February 1, 2010, and July 1, 2017.

EXPOSURES

Parental socioeconomic measures, including maternal educational level, occupation, paternal educational level, and neighborhood income based on median annual household income.

MAIN OUTCOMES AND MEASURES

Mean relative TL was measured in cord blood and placental tissue. By constructing a principal component, an integrative socioeconomic measure was derived that integrates parental socioeconomic status and neighborhood income. Multivariable adjusted regression analyses were performed to associate the integrative socioeconomic measure and TL at birth.

RESULTS

In 1026 newborns (517 boys; mean [SD] gestational age, 39.2 [1.4] weeks), a higher socioeconomic status was associated with longer cord blood TL and placental TL. Each unit increment in the integrative socioeconomic status measure was associated with 2.1% (95% CI, 0.9%-3.4%; P < .001) longer cord blood TL in boys, while no association was observed for girls (0.5% longer cord blood TL; 95% CI, -0.9% to 1.8%; P = .50). The sex-specific socioeconomic status interaction revealed a stronger association in boys compared with newborn girls (1.6%; 95% CI, 0.02%-3.3%; P = .047 for interaction). In placental tissue, higher socioeconomic status was associated with 1.8% (95% CI, 0.3%-3.3%; P = .02) longer TL in newborn boys but not in girls (0.4% longer TL; 95% CI, -1.2% to 2.0%; P = .63). For placental tissue, no sex and socioeconomic status interaction on TL was observed (1.4%; 95% CI, -0.5% to 3.4%; P = .16 for interaction).

CONCLUSIONS AND RELEVANCE

This study suggests that parental socioeconomic status is associated with newborn TL, especially in boys. The results indicate that familial social economic factors are associated with the potential cellular longevity of the next generation, with a potential higher transgenerational vulnerability for newborn boys.

The influence of lifecourse financial strains on the later-life health of the Japanese as assessed by four models based on different health indicators

In this study, four models used for assessing the influence of lifecourse financial strains on later-life health (the latent period effects, pathway, social mobility and accumulative effects models) were tested in the context of Japan by using different types of health indicators: comorbidity, disabled activities of daily living, disabled cognitive function, self-rated health and depressive symptoms. We hypothesised that suitable models for describing the influence of financial strain would differ according to the type of health indicator used. Participants aged 60–92 years (N = 2,500) were obtained in 2012 by using a two-stage stratified random sampling method. The final number of participants in the sample was 1,324. The results indicate that three models – pathway, accumulative effects and social mobility – describe the influence of a person's lifecourse financial strain on comorbidity, cognitive function, self-rated health and depressive symptoms. In turn, the latent period effects model explains the influence of lifecourse financial strain on comorbidity. However, only the pathway model described the influence of lifecourse financial strain on activities of daily living. These results suggest that disadvantages in lifecourse socio-economic status influence the decline of health in elderly Japanese people, similar to people in Western countries. However, the finding that suitable models for describing the influence of socio-economic status on health will differ according to the type of health indicator is an original contribution of this study.

Family of origin and educational inequalities in mortality: Results from 1.7 million Swedish siblings

Circumstances in the family of origin have short- and long-term consequences for people's health. Family background also influences educational achievements - achievements that are clearly linked to various health outcomes. Utilizing population register data, we compared Swedish siblings with different levels of education (1,732,119 individuals within 662,095 sibships) born between 1934 and 1959 and followed their death records until the end of 2012 (167,932 deaths). The educational gradient in all-cause mortality was lower within sibships than in the population as a whole, an attenuation that was strongest at younger ages (< 50 years of age) and for those with a working class or farmer background. There was substantial variation across different causes of death with clear reductions in educational inequalities in, e.g., lung cancer and diabetes, when introducing shared family factors, which may indicate that part of the association can be ascribed to circumstances that siblings have in common. In contrast, educational inequalities in suicide and, for women, other mental disorders increased when adjusting for factors shared by siblings. The vast variation in the role of childhood conditions for the education-mortality association may help us to further understand the interplay between family background, education, and mortality. The increase in the education gradient in suicide when siblings are compared may point towards individually oriented explanations ('non-shared environment'), perhaps particularly in mental disorders, while shared family factors primarily seem to play a more important role in diseases in which health behaviors are most significant.

Support Buffers Financial Strain's Effect on Health-related Quality of Life

OBJECTIVES

Financial strain represents a perceived inability to meet financial needs and obligations and is associated with poorer health outcomes. Distinct facets of perceived social support may mitigate the deleterious effects of financial strain on health. In the present study, we examined the extent to which appraisal, belonging, and tangible social support ameliorate the effects of financial strain on health-related quality of life (HRQoL).

METHODS

A community sample (N = 238; 67.2% female; MAge = 43.4 years, SD = 13.1) completed inperson surveys as part of a larger study of health behaviors.

RESULTS

Greater financial strain and less social support were associated with poorer HRQoL. Additionally, both appraisal and belonging support moderated the effects of financial strain on some HRQoL components, such that higher appraisal and belonging support were associated with diminished effects of financial strain on HRQoL.

CONCLUSIONS

These findings suggest nuanced associations between financial strain and HRQoL. We discuss the implications for prevention and intervention programs.

Intergenerational social mobility and leisure-time physical activity in adulthood: a systematic review

Aim

To systematically review the association between intergenerational social mobility and leisure-time physical activity (LTPA) in adulthood, in order to assess all published evidence relating to the hypothesis that adults socially mobile between childhood and adulthood will have different levels of LTPA than those in the same socioeconomic group across life.

Methods

A systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were identified by searching databases (MEDLINE, Embase, PsycINFO) and reference lists. Eligible studies examined associations between any indicator of social mobility, based on at least one measure of parental socioeconomic position (SEP) and one measure of own adult SEP, and LTPA in adulthood.

Results

13 studies comprising a total of 44 000 participants from the UK, Finland, Sweden, Australia, USA and Brazil were included. Participants were aged 16–70 years and were from population-based surveys, occupational cohorts and primary care registries. Most studies (n=9) used occupational class measures to identify social mobility; education (n=4) and income (n=1) were also used. There was consistent evidence in nine of the 13 studies that stable high socioeconomic groups tended to report the highest levels of participation in LTPA and stable low socioeconomic groups the lowest. Upward and downwardly mobile groups participated in LTPA at levels between these stable groups.

Conclusions

Cumulative exposure to higher SEP in childhood and adulthood was associated with higher LTPA in adulthood. Thus, a potential outcome of policies and interventions which aim to minimise exposure to socioeconomic adversity may be increased LTPA among adults.

Trial registration number

CRD42016036538.

Association between education and future leisure-time physical inactivity: a study of Finnish twins over a 35-year follow-up

Background

Education is associated with health related lifestyle choices including leisure-time physical inactivity. However, the longitudinal associations between education and inactivity merit further studies. We investigated the association between education and leisure-time physical inactivity over a 35-year follow-up with four time points controlling for multiple covariates including familial confounding.

Methods

This study of the population-based Finnish Twin Cohort consisted of 5254 twin individuals born in 1945–1957 (59 % women), of which 1604 were complete same-sexed twin pairs. Data on leisure-time physical activity and multiple covariates was available from four surveys conducted in 1975, 1981, 1990 and 2011 (response rates 72 to 89 %). The association between years of education and leisure-time physical inactivity (<1.5 metabolic equivalent hours/day) was first analysed for each survey. Then, the role of education was investigated for 15-year and 35-year inactivity periods in the longitudinal analyses. The co-twin control design was used to analyse the potential familial confounding of the effects. All analyses were conducted with and without multiple covariates. Odds Ratios (OR) with 95 % Confidence Intervals (CI) were calculated using logistic and conditional (fixed-effects) regression models.

Results

Each additional year of education was associated with less inactivity (OR 0.94 to 0.95, 95 % CI 0.92, 0.99) in the cross-sectional age- and sex-adjusted analyses. The associations of education with inactivity in the 15- and 35-year follow-ups showed a similar trend: OR 0.97 (95 % CI 0.93, 1.00) and OR 0.94 (95 % CI 0.91, 0.98), respectively. In all co-twin control analyses, each year of higher education was associated with a reduced likelihood of inactivity suggesting direct effect (i.e. independent from familial confounding) of education on inactivity. However, the point estimates were lower than in the individual-level analyses. Adjustment for multiple covariates did not change these associations.

Conclusions

Higher education is associated with lower odds of leisure-time physical inactivity during the three-decade follow-up. The association was found after adjusting for several confounders, including familial factors. Hence, the results point to the conclusion that education has an independent role in the development of long-term physical inactivity and tailored efforts to promote physical activity among lower educated people would be needed throughout adulthood.

Alcohol-related morbidity and mortality within siblings

AIMS

To estimate the association between educational status and alcohol-related somatic and non-somatic morbidity and mortality among full siblings in comparison with non-related individuals.

DESIGN

Cohort study.

SETTING

Denmark.

PARTICIPANTS

Approximately 1.4 million full siblings born in Denmark between 1950 and 1979 were followed from age 28-58 years or censoring due to alcohol-related hospitalization and mortality.

MEASUREMENTS

Cox regression analyses were used to estimate associations of educational status with alcohol-related outcomes. Results from cohort analyses based on non-related individuals and inter-sibling analyses were compared.

FINDINGS

A lower educational status was associated with a higher rate of alcohol-related outcomes, especially among the youngest (aged 28-37 years) and individuals born 1970-79. Compared with the cohort analyses, the associations attenuated slightly in the inter-sibling analysis. For example, in the cohort analysis, females with a basic school education born 1970-79 had an increased rate of alcohol-related non-somatic morbidity and mortality [hazard rate ratio (HR) = 4.05, 95% confidence interval (CI) = 3.27-5.02] compared to those with a vocational education. In the inter-sibling analysis, the HR attenuated (HR = 2.66, 95% CI = 1.95-3.63). For alcohol-related somatic outcomes the corresponding figures were HR = 3.47 (95% CI = 2.63-4.58) and HR = 3.36 (95% CI = 2.10-5.38), respectively. In general, the associations were stronger among females than males (aged 28-37) in the analyses of alcohol-related non-somatic outcomes. Health conditions earlier in life explained only a minor part of the associations.

CONCLUSIONS

The association between educational status and alcohol-related somatic and non-somatic morbidity and mortality is only driven by familial factors to a small degree.

Difference in health inequity between two population groups due to a social determinant of health

The World Health Organization defines social determinants of health as "complex, integrated, and overlapping social structures and economic systems" that are responsible for most health inequities. Similar to the individual-level risk factors such as behavioral and biological risk factors that influence disease, we consider social determinants of health such as the distribution of income, wealth, influence and power as risk factors for risk of disease. We operationally define health inequity in a disease within a population due to a risk factor that is unfair and avoidable as the difference between the disease outcome with and without the risk factor in the population. We derive expressions for difference in health inequity between two populations due to a risk factor that is unfair and avoidable for a given disease. The difference in heath inequity between two population groups due to a risk factor increases with increasing difference in relative risks and the difference in prevalence of the risk factor in the two populations. The difference in health inequity could be larger than the difference in health outcomes between the two populations in some situations. Compared to health disparities which are typically measured and monitored using absolute or relative disparities of health outcomes, the methods presented in this manuscript provide a different, yet complementary, picture because they parse out the contributions of unfair and avoidable risk factors.

Financial strain and self-rated health among Black adults

OBJECTIVES

To explore associations between financial strain and self-rated health among 1341 black adults.

METHODS

Associations were investigated using a covariate-adjusted linear regression model. Mediation (via stress and/or depressive symptoms) was explored in additional models using a nonparametric bootstrapping procedure.

RESULTS

Higher financial strain was associated with poorer self-rated health (p < .001). Stress and depressive symptoms were each significant mediators of this relation in both single and multiple mediator models (p values < .05).

CONCLUSIONS

Financial strain may contribute to poorer health among black adults, partially via greater stress and depressive symptoms. Potential theoretical, intervention, and policy implications are discussed. Future studies with longitudinal designs are needed to confirm these results.

Are the educational differences in incidence of cardiovascular disease explained by underlying familial factors? A twin study

To isolate the effect of education from the influence of potential underlying factors, we investigated the association of education with the risk of cardiovascular disease (CVD) and ischemic heart disease (IHD) using twin data to adjust for familial factors shared within twins, including genetic make-up and childhood environment. The study was based on data from the Danish Twin Registry linked to administrative and heath registers in Statistics Denmark. A total of 11,968 monozygotic and 20,464 dizygotic same sexed twins were followed from 1980 to 2009, including more than 8000 events of CVD. Unpaired and intra-pair analyses were compared. In the unpaired analyses, an inverse educational gradient in CVD- and IHD risk was observed. This association was not replicated in the intra-pair analyses that control for shared familial factors exploiting that twins share their intrauterine- and childhood environment and are matched partly or fully on genetic setup. The attenuation of association of education with CVD and IHD in the intra-pair analyses suggests that shared familial factors account for a substantial part of the observed association of education with CVD and IHD in Denmark.

Are familial factors underlying the association between socioeconomic position and prescription medicine? A register-based study on Danish twins

OBJECTIVES

Although well established, the association between socioeconomic position and health and health behaviour is not clearly understood, and it has been speculated that familial factors, for example, dispositional factors or exposures in the rearing environment, may be underlying the association. The objective was to compare prescription fillings within twin pairs who are partly or fully genetically identical and share childhood exposures.

DESIGN

Twin cohort study.

SETTING

Denmark.

PARTICIPANTS

Data from the Danish Twin Registry were linked to registers in Statistics Denmark and the Danish Registry of Medicinal Product statistics. A total of 8582 monozygotic (MZ) and 15 788 dizygotic same sex (DZSS) twins were included.

OUTCOME MEASURES

Number of prescription fillings during follow-up (1995-2005) was analysed according to education and income. Results of unpaired and intrapair analyses were compared.

RESULTS

An inverse social gradient in filling of prescriptions for all-purpose and system-specific drugs was observed in the unpaired analyses. In the intrapair analyses, associations were attenuated some in DZSS and more in MZ twins. Filling of drugs targeting the nervous system was still strongly associated with income in the intrapair analyses.

CONCLUSIONS

Familial factors seem to account for part of the observed social inequality in filling of prescription medicine.

History, biology, and health inequities: emergent embodied phenotypes and the illustrative case of the breast cancer estrogen receptor

How we think about biology--in historical, ecological, and societal context--matters for framing causes of and solutions to health inequities. Drawing on new insights from ecological evolutionary developmental biology and ecosocial theory, I question dominant gene-centric and ultimately static approaches to conceptualizing biology, using the example of the breast cancer estrogen receptor (ER). Analyzed in terms of its 4 histories--societal, individual (life course), tumor (cellular pathology), and evolutionary--the ER is revealed as a flexible characteristic of cells, tumors, individuals, and populations, with magnitudes of health inequities tellingly changing over time. This example suggests our science will likely be better served by conceptualizing disease and its biomarkers, along with changing magnitudes of health inequities, as embodied history--that is, emergent embodied phenotype, not innate biology.

Does shared family background influence the impact of educational differences on early mortality?

The mechanisms behind social differences in mortality rates have been debated. The authors examined the extent to which shared family background and health in early life could explain the association between educational status and all-cause mortality rates using a sibling design. The study was register-based and included all individuals born in Denmark between 1950 and 1979 who had at least 1 full sibling born in the same time period (n = 1,381,436). All individuals were followed from 28 years of age until death, emigration, or December 2009. The authors used Cox regression analyses to estimate hazard ratios for mortality according to educational level. Conventional cohort and intersibling analyses were carried out and conducted separately for deaths occurring before and after the age of 45 years, respectively. The cohort analyses showed an inverse association between educational status and all-cause mortality that was strongest for males, increased with younger birth cohorts, and tended to be strongest in the analyses of death before 45 years of age. The associations were attenuated slightly in the intersibling analyses and after adjustment for serious health conditions in early life. Hence, health selection and confounding by factors shared by siblings explained only a minor part of the association between educational level and all-cause mortality.

Education and adult cause-specific mortality--examining the impact of family factors shared by 871 367 Norwegian siblings

OBJECTIVE

To estimate the impact family factors shared by siblings has on the association between length of education and cause-specific mortality in adulthood.

METHODS

The study population (n = 871 367) was all Norwegians born 1940-59 having one or more sibling within the cohort and alive in 1990. Length of education was obtained in 1990. Follow-up of deaths was from 1991 to 2008 when participants were aged 32-68 years.

RESULTS

Sixty-five per cent of participants had one or more siblings who had completed a different number of years of formal education. A one-category difference in education was associated with a 30% increase in the hazard rate of death by all causes among men in the cohort analysis and 23% in within siblings analysis, and in women, increases were 22% and 14%, respectively. For cardiovascular disease, increases were 36% and 25% in men and 51% and 36% in women. For lung cancer, they were 48% and 29% in men and 53% and 22% in women. External causes and alcohol-related causes in men were generally similar in both analyses.

CONCLUSIONS

This study suggests that at least some of the educational inequalities in all-cause, cardiovascular disease and lung cancer, external and alcohol-related mortality are explained by factors shared by siblings.

Socioeconomic inequality in birth weight and gestational age in Denmark 1996-2007: using a family-based approach to explore alternative explanations

A large body of literature has reported associations between socioeconomic position and adverse pregnancy outcomes even in affluent egalitarian welfare states. This study explored the nature of this relationship by examining women who changed socioeconomic position between pregnancies and women who were siblings but were different in terms of socioeconomic position. Data consisted of 471,215 live born singletons born in Denmark 1997-2007 with at least one sibling or one first cousin. We examined parental educational attainment and household income in relation to preterm birth and small for gestational age using Cox regression. Household income was only weakly related to these outcomes. Paternal education was strongly associated with the outcomes only in the cohort analyses. Maternal education was inversely associated with preterm birth only in the cohort analyses, where the least educated women had the highest risk. Maternal education was inversely associated with the risk of small for gestational age in cohort analyses, attenuated between mothers who were siblings, and not present between children who were siblings. For example, the hazard ratio of preterm birth of women with a college/university degree when compared to women with only mandatory education was 0.64 (95% confidence interval: 0.60-0.67) in the cohort analysis, 0.90 (0.78-1.04) between mothers who were siblings, and 1.01 (0.82-1.24) between children who were siblings. The corresponding hazard ratios of small for gestational age were 0.54 (0.52-0.56), 0.72 (0.63-0.83), and 1.02 (0.84-1.24). This suggests that the associations were partly explained by factors shared between mothers who are siblings. In conclusion, the early life circumstances of mothers appear to be important in understanding the association between education, preterm birth and small for gestational age.

Antagonistic pleiotropy at the human IL6 promoter confers genetic resilience to the pro-inflammatory effects of adverse social conditions in adolescence

The authors tested the evolutionary genetic hypothesis that the functional form of an asymmetrically risky Gene × Environment interaction will differ as a function of age-related antagonistic pleiotropy (i.e., show opposite effects in young vs. old individuals). Previous studies have identified a polymorphism in the human IL6 promoter (rs1800795; IL6-74 G/C) that interacts with adverse socioenvironmental conditions to promote chronic inflammation in older adults (elevated C-reactive protein). This study identifies a protective effect of the same polymorphism in 17- to 19-year-old adolescents confronting socioeconomic adversity. Over 60% of the environmental risk contribution to the IL6 × Socioeconomic Status interaction could be accounted for by interpersonal stress and adult role burden. Thus, the IL6-174G allele does not represent an undifferentiated risk factor but instead sensitizes inflammatory biology to socioenvironmental conditions, conferring either genetic vulnerability or resilience depending on the developmental "somatic environment" that interacts with social conditions to influence gene expression.

Register-based research on twins

INTRODUCTION

The Danish Twin Registry (DTR) has for more than 50 years been based on surveys and clinical investigations and over the two last decades also on register linkage. Currently these two approaches are merged within Statistics Denmark.

RESEARCH TOPICS

Here we report on three major groups of register-based research in the DTR that used the uniqueness of twinning. First, we focus on the ''long-term prognosis'' of being a twin compared with being a singleton and show that Danish twins have health trajectories in adulthood similar to singletons, which is a result of interest for twins and their families as well as a test of the fetal origins hypothesis that states that fetal growth restriction has long-term health consequences. Secondly, we summarise some of the most important register-based ''classical twin studies'', e.g. heritability studies on lifespan and exceptional longevity. Finally, we illustrate how the co-twin control method in a register setting can be used to control for the effect of rearing environment and genetic factors in studies of the association between exposures and health.

CONCLUSION

The spectrum of register-based twin studies is very wide and have changed in accordance with methodological and data resource developments.

The association between blood pressure and years of schooling versus educational credentials: test of the sheepskin effect

PURPOSE

Attaining a degree may offer greater opportunities for health than years of schooling alone. This study examines whether there is a degree, or "sheepskin," effect on the association between education and blood pressure.

METHODS

Multivariable-adjusted ordinal and linear regression models assessed associations of years of schooling and degree attainment with systolic and diastolic blood pressure in a sample of 552 adults ages 38 to 47 years.

RESULTS

Years of schooling was inversely associated with systolic blood pressure adjusting for age, gender and race (β = -0.4, 95% confidence limit: -0.7, -0.1 mmHg systolic blood pressure/year of schooling). Additional adjustment for mother's education, childhood verbal intelligence quotient, childhood health, and childhood socioeconomic status had minimal impact on effect size (β = -0.3, 95% confidence limit = -0.7, 0.0). However, years of schooling was no longer associated with blood pressure in the fully adjusted model which included additional adjustment for degree attained (β = 0.0, 95% confidence limit: -0.5, 0.4). In the fully adjusted model (including adjustment for years of schooling), individuals with a graduate degree still had significantly lower systolic blood pressure than HS degree-holders (e.g., β = -9.2, 95% confidence limit: -15.2, -3.2 for graduate vs high school degree). Findings were similar for diastolic blood pressure.

CONCLUSIONS

The association of years of schooling with blood pressure may be largely due to degree attainment rather than simply the knowledge and skills accumulated due to years of schooling alone.

Does educational status impact adult mortality in Denmark? A twin approach

To disentangle an independent effect of educational status on mortality risk from direct and indirect selection mechanisms, the authors used a discordant twin pair design, which allowed them to isolate the effect of education by means of adjustment for genetic and environmental confounding per design. The study is based on data from the Danish Twin Registry and Statistics Denmark. Using Cox regression, they estimated hazard ratios for mortality according to the highest attained education among 5,260 monozygotic and 11,088 dizygotic same-sex twin pairs born during 1921–1950 and followed during 1980–2008. Both standard cohort and intrapair analyses were conducted separately for zygosity, gender, and birth cohort. Educational differences in mortality were demonstrated in the standard cohort analyses but attenuated in the intrapair analyses in all subgroups but men born during 1921–1935, and no effect modification by zygosity was observed. Hence, the results are most compatible with an effect of early family environment in explaining the educational inequality in mortality. However, large educational differences were still reflected in mortality risk differences within twin pairs, thus supporting some degree of independent effect of education. In addition, the effect of education may be more pronounced in older cohorts of Danish men.

Life-course financial strain and health in African-Americans

Differential exposure to financial strain may explain some differences in population health. However, few studies have examined the cumulative health effect of financial strain across the life-course. Studies that have are limited to self-reported health measures. Our objective was to examine the associations between childhood, adulthood, and life-course, or cumulative, financial strain with disability, lung function, cognition, and depression. In a population-based cross-sectional cohort study of adult African-American twins enrolled in the US Carolina African American Twin Study of Aging (CAATSA), we found that participants who reported financial strain as children and as adults are more likely to be physically disabled, and report more depressive symptoms than their unstrained counterparts. Participants who reported childhood financial strain had lower cognitive functioning than those with no childhood financial strain. We were unable to detect a difference in lung function beyond the effect of actual income and education in those who reported financial strain compared to those who did not. Financial strain in adulthood was more consistently associated with poor health than was childhood financial strain, a finding that suggests targeting adult financial strain could help prevent disability and depression among African-American adults.

Education in time: cohort differences in educational attainment in African-American twins

OBJECTIVES

Educational opportunities for African-Americans expanded throughout the 20(th) century. Twin pairs are an informative population in which to examine changes in educational attainment because each twin has the same parents and childhood socioeconomic status. We hypothesized that correlation in educational attainment of older twin pairs would be higher compared to younger twin pairs reflecting changes in educational access over time and potentially reflecting a "ceiling effect" associated with Jim Crow laws and discrimination.

METHODOLOGY AND PRINCIPAL FINDINGS

We used data from 211 same-sex twin pairs (98 identical, 113 fraternal) in the Carolina African-American Twin Study of Aging who were identified through birth records. Participants completed an in-person interview. The twins were predominantly female (61%), with a mean age of 50 years (SD = 0.5). We found that older age groups had a stronger intra-twin correlation of attained educational level. Further analysis across strata revealed a trend across zygosity, with identical twins demonstrating more similar educational attainment levels than did their fraternal twin counterparts, suggesting a genetic influence.

DISCUSSION

These findings suggest that as educational opportunities broadened in the 20th century, African-Americans gained access to educational opportunities that better matched their individual abilities.

Socioeconomic position and twins' health: a life-course analysis of 1266 pairs of middle-aged Danish twins

BACKGROUND

The association between socioeconomic circumstances and health in adulthood could come about through processes that may be divided into factors experienced early in life and those experienced in later adulthood. In order to disentangle the influences on health of the early genetic, prenatal and rearing environmental factors from environmental factor later in life, we compared the health status among male and female twin pairs who lived together during childhood and were discordant or concordant on adult socioeconomic position.

METHODS

A cross-sectional survey among a random sample of middle-aged Danish twins was conducted in 1998-99. The study population included 1266 like-sex twin pairs [52.5% monozygotic (MZ) and 47.6% dizygotic (DZ)]. Data were obtained on childhood and adult social class and on height, BMI, grip strength, depression symptoms, self-rated health, cognitive function, physical activity, smoking, alcohol and food intake.

RESULTS

The expected associations between the individual twins' adult social class and health measures were observed. Among DZ male twins discordant on adult social class, the higher social class twin was on average significantly taller and had higher cognitive test scores. Among DZ female twins discordant on adult social class, the higher social class female twin was more physically active and had a higher cognitive test score. There were no significant health disparities or behavioural differences between the members of MZ twin pairs discordant on adult social class. For most health outcomes, the variability within twin pairs was related to zygosity (higher for DZ than for MZ) but not to social class.

CONCLUSION

This study suggests that the relationship between adult social class and health outcomes in Denmark is due mainly to selection effects rather than a causal effect of social class exposures on health and behaviour.

Henipaviruses: emerging paramyxoviruses associated with fruit bats

Two related, novel, zoonotic paramyxoviruses have been described recently. Hendra virus was first reported in horses and thence humans in Australia in 1994; Nipah virus was first reported in pigs and thence humans in Malaysia in 1998. Human cases of Nipah virus infection, apparently unassociated with infection in livestock, have been reported in Bangladesh since 2001. Species of fruit bats (genus Pteropus) have been identified as natural hosts of both agents. Anthropogenic changes (habitat loss, hunting) that have impacted the population dynamics of Pteropus species across much of their range are hypothesised to have facilitated emergence. Current strategies for the management of henipaviruses are directed at minimising contact with the natural hosts, monitoring identified intermediate hosts, improving biosecurity on farms, and better disease recognition and diagnosis. Investigation of the emergence and ecology of henipaviruses warrants a broad, cross-disciplinary ecosystem health approach that recognises the critical linkages between human activity, ecological change, and livestock and human health.

Human monoclonal antibody combination against SARS coronavirus: synergy and coverage of escape mutants

BACKGROUND

Experimental animal data show that protection against severe acute respiratory syndrome coronavirus (SARS-CoV) infection with human monoclonal antibodies (mAbs) is feasible. For an effective immune prophylaxis in humans, broad coverage of different strains of SARS-CoV and control of potential neutralization escape variants will be required. Combinations of virus-neutralizing, noncompeting mAbs may have these properties.

METHODS AND FINDINGS

Human mAb CR3014 has been shown to completely prevent lung pathology and abolish pharyngeal shedding of SARS-CoV in infected ferrets. We generated in vitro SARS-CoV variants escaping neutralization by CR3014, which all had a single P462L mutation in the glycoprotein spike (S) of the escape virus. In vitro experiments confirmed that binding of CR3014 to a recombinant S fragment (amino acid residues 318-510) harboring this mutation was abolished. We therefore screened an antibody-phage library derived from blood of a convalescent SARS patient for antibodies complementary to CR3014. A novel mAb, CR3022, was identified that neutralized CR3014 escape viruses, did not compete with CR3014 for binding to recombinant S1 fragments, and bound to S1 fragments derived from the civet cat SARS-CoV-like strain SZ3. No escape variants could be generated with CR3022. The mixture of both mAbs showed neutralization of SARS-CoV in a synergistic fashion by recognizing different epitopes on the receptor-binding domain. Dose reduction indices of 4.5 and 20.5 were observed for CR3014 and CR3022, respectively, at 100% neutralization. Because enhancement of SARS-CoV infection by subneutralizing antibody concentrations is of concern, we show here that anti-SARS-CoV antibodies do not convert the abortive infection of primary human macrophages by SARS-CoV into a productive one.

CONCLUSIONS

The combination of two noncompeting human mAbs CR3014 and CR3022 potentially controls immune escape and extends the breadth of protection. At the same time, synergy between CR3014 and CR3022 may allow for a lower total antibody dose to be administered for passive immune prophylaxis of SARS-CoV infection.