Predictors of physical health: toward an integrated model of genetic and environmental antecedents

Spatial and temporal expression patterns of genes around nine neuroticism-associated loci

Neuroticism is a high-order personality trait. Individuals with higher neuroticism have increased risks of various psychiatric disorders and physical health outcomes. Neuroticism is related to physiological differences in the brain. A recent genome-wide association study identified nine distinct genomic loci that contribute to neuroticism. Brain development and function depend on the precise regulation of gene expression, which is differentially regulated across brain regions and developmental stages. Using multiple publicly available human post-mortem databases, we investigated, in brain and non-brain tissues and across several developmental life stages, the spatial and temporal expression patterns of genes arising from nine neuroticism-associated loci. Functional gene-network analysis for neuroticism-associated genes was performed. The spatial expression analysis revealed that the nearest genes (GRIK3, SRP9, KLHL2, PTPRD, ELAVL2, CRHR1 and CELF4) from index single-nucleotide polymorphisms (SNPs) at the nine loci were intensively enriched in the brain compared with their representation in non-brain tissues (p<1.56×10^-3). The nearest genes associated with the glutamate receptor activity network consisted mainly of GRIK3 (FDR q=4.25×10^-2). The temporal expression analysis revealed that the neuroticism-associated genes were divided into three expression patterns: KLHL2, CELF4 and CRHR1 were preferentially expressed during postnatal stages; PTPRD, ELAVL2 and MFHAS1 were expressed during prenatal stages; and the other three genes were not expressed during specific life stages. These findings suggest that the glutamate network might be a target for investigating the neurobiological mechanisms underlying susceptibilities to higher neuroticism and several psychiatric disorders and that neuroticism is mediated by genes specifically expressed in the brain during several developmental stages.

Nonspousal Family Loss among Community-Dwelling Older Adults

We examined the prevalence and correlates of recent nonspousal family loss among older adults using data from the University of Alabama at Birmingham Study of Aging, a stratified random sample of community-dwelling older adults living in central Alabama. Twenty-three percent of participants reported a recent nonspousal family loss. African American ethnicity, education <12th grade, functional difficulty, restricted life-space mobility, depressive symptomology, pain and other somatic symptoms were associated with recent nonspousal family loss. Compared to non-widowed participants, widows with family loss reported a higher proportion of mental health and activity-limiting physical problems as well as restricted life-space. Programs to improve physical function and enhance health and wellbeing in older bereaved spouses should be expanded to include older adults with nonspousal family loss, particularly targeting the mental health needs of previously widowed persons who lose another family member.

Genetic and Environmental Overlap Between Childhood Maltreatment and Adult Physical Health

Past research demonstrates a phenotypic relationship between childhood maltreatment and adult health problems. Explanations of this association usually point to either: (a) a direct causal link, whereby exposure to early stress disrupts biological functioning during sensitive periods of development; or (b) an indirect effect operating through socioeconomic attainment, poor health behaviors, or some other pathway leading from childhood to adulthood. The current study examined whether the association between childhood maltreatment and adult health reflects genetic or environmental mediation. Using a large sample of adult American twins, we separately estimated univariate biometric models of child maltreatment and adult physical health, followed by a bivariate biometric model to estimate genetic and environmental correlations between the two variables. We found that a summary count of chronic health conditions shared non-trivial genetic overlap with childhood maltreatment. Our results have implications for understanding the relationship between maltreatment and health as one of active interplay rather than a simple cause and effect model that views maltreatment as an exogenous shock.

Socio-Genomics and Structural Competency

Adverse developmental exposures and pathologies of the social environment make vastly greater contributions to the leading health burdens in society than currently known genotypic information. Yet, while patients now commonly bring information on single alleles to the attention of their healthcare team, the former conditions are only rarely considered with respect to future health outcomes. This manuscript aims to integrate social environmental influences in genetic predictive models of disease risk. Healthcare providers must be educated to better understand genetic risks for complex diseases and the specific health consequences of societal adversities, to facilitate patient education, disease prevention, and the optimal care in order to achieve positive health outcomes for those with early trauma or other social disadvantage.

Genetic strategies for probing conscientiousness and its relationship to aging

Conscientiousness is an important trait for understanding healthy aging. The present article addresses how behavioral and molecular genetics methodologies can aid in furthering explicating the link between conscientiousness and aspects of health and well-being in later life. We review the etiology of conscientiousness documented by both quantitative and molecular genetics methods. We also discuss the ways behavior genetics can be used to continue to help refine the concept of conscientiousness and to help identify points of etiological overlap between conscientiousness and healthy aging outcomes. Phenotypic research has established nontrivial associations between conscientiousness and important outcomes, but behavior genetic methods can determine what the causal (genetic and environmental) mechanisms are behind these relationships. An empirical example of one of these techniques is provided using twin data from the Midlife in the United States (MIDUS) study. We demonstrate that conscientiousness moderates genetic and environmental influences on problem alcohol use, such that greater levels of conscientiousness buffer against the random effects of the environment. Finally, suggestions for future work in this area are discussed.

A behavioral genetic investigation of weekend drinking among an adult sample

This study examined common and unique genetic and environmental influences on weekend drinking and weekday drinking reported by US male and female adult participants (mean age = 43.9). Data from 96 monozygotic and 82 dizygotic twin pairs were used to estimate bivariate biometric models of daily levels of weekend and weekday drinking volume. Weekend and weekday drinking volume scores were calculated from end-of-day reports of drinking across eight days. As expected, more drinking occurred during weekends. Biometric models provided evidence of significant additive genetic and nonshared environmental influences on both weekend and weekday drinking. Shared environmental influences were nonsignificant. Genetic influences accounted for a greater proportion of drinking variance during weekdays than weekends (0.36 compared to 0.17). However, these apparent differences in heritability-proportion of total variance accounted for by genetic variance-were due to increased nonshared environmental influences on weekend days, rather than greater genetic influences. The study's limitations are noted. Funded by National Institutes of Health/National Institute of Aging and John D. and Catherine T. MacArthur Foundation.

The association between parent's health and the educational attainment of their children

In this paper we compare the educational attainment of adults who had relatively unhealthy parents when they were adolescents to those whose parents were relatively healthy during this time of their lives. We use data from the National Longitudinal Study of Adolescent Health (n = 13,556) to show that U.S. adolescents whose parents described their health as "fair" or "poor" at Wave 1 of the study were more likely to drop out of high school compared to those whose parents reported better levels of health. We do not observe any association between parental health and the likelihood of attending college among those who graduated from high school, however we do show that completing college (among college attendees) is more likely among those whose parents reported better health when they were adolescents. This association persists despite a wide range of statistical controls including socioeconomic status of the household, the physical and mental health status of the respondent, the grade point average of the respondent, the health behaviors of parents, as well as parental time investment. These findings add an important intergenerational component to research on the relationship between socioeconomic status and health.

Pain and depression in late life: mastery as mediator and moderator

OBJECTIVES

This study examines how mastery mediates and moderates the relationship between pain and depression among older adults, as well as the extent to which these processes differ by the timing of pain in late life, while utilizing statistical methods that comprehensively control for time-stable confounds.

METHODS

Data are derived from multiple observations of adults aged 65 years and older in the Washington, DC, metropolitan area over a 4-year period. Fixed effects models are used to control for time-stable influences.

RESULTS

With all time-stable influences controlled, pain is positively related to symptoms of depression, although this relationship is substantially reduced in comparison with a model in which all time-stable confounds are not held constant. Mastery does not mediate this relationship because pain is not significantly related to mastery once time-stable factors are taken into account. Mastery buffers the relationship between pain and depression, but only for elders later in late life.

DISCUSSION

This study suggests that a synthesis of stress process and life course perspectives is critical for understanding how pain influences depression in late life. However, research that does not comprehensively control for time-stable factors may overestimate the consequences of pain for older adults.

Protective Factors in Midlife

The detection of psychological variables with a positive impact on health during middle age is of great interest. The data of 393 middle-aged participants (aged 35–45 at T1 and 45–55 at T2) of the National Survey of Midlife Development in the United States (MIDUS) were analyzed to investigate the associations between health, optimism, positive affect, social support, and a cumulative burden score. Results show a positive association of the protective factors and a predictive value of positive emotions on health over time. The burden score showed no unique association with health. Overall, the predictors explained 17% of the variance of physical health and 33% of the variance of mental health. These findings emphasize the importance of investigating protective pathways.

The establishment of the GENEQOL consortium to investigate the genetic disposition of patient-reported quality-of-life outcomes

To our knowledge, no comprehensive, interdisciplinary initiatives have been taken to examine the role of genetic variants on patient-reported quality-of-life outcomes. The overall objective of this paper is to describe the establishment of an international and interdisciplinary consortium, the GENEQOL Consortium, which intends to investigate the genetic disposition of patient-reported quality-of-life outcomes. We have identified five primary patient-reported quality-of-life outcomes as initial targets: negative psychological affect, positive psychological affect, self-rated physical health, pain, and fatigue. The first tangible objective of the GENEQOL Consortium is to develop a list of potential biological pathways, genes and genetic variants involved in these quality-of-life outcomes, by reviewing current genetic knowledge. The second objective is to design a research agenda to investigate and validate those genes and genetic variants of patient-reported quality-of-life outcomes, by creating large datasets. During its first meeting, the Consortium has discussed draft summary documents addressing these questions for each patient-reported quality-of-life outcome. A summary of the primary pathways and robust findings of the genetic variants involved is presented here. The research agenda outlines possible research objectives and approaches to examine these and new quality-of-life domains. Intriguing questions arising from this endeavor are discussed. Insight into the genetic versus environmental components of patient-reported quality-of-life outcomes will ultimately allow us to explore new pathways for improving patient care. If we can identify patients who are susceptible to poor quality of life, we will be able to better target specific clinical interventions to enhance their quality of life and treatment outcomes.

Public health significance of neuroticism

The personality trait of neuroticism refers to relatively stable tendencies to respond with negative emotions to threat, frustration, or loss. Individuals in the population vary markedly on this trait, ranging from frequent and intense emotional reactions to minor challenges to little emotional reaction even in the face of significant difficulties. Although not widely appreciated, there is growing evidence that neuroticism is a psychological trait of profound public health significance. Neuroticism is a robust correlate and predictor of many different mental and physical disorders, comorbidity among them, and the frequency of mental and general health service use. Indeed, neuroticism apparently is a predictor of the quality and longevity of our lives. Achieving a full understanding of the nature and origins of neuroticism, and the mechanisms through which neuroticism is linked to mental and physical disorders, should be a top priority for research. Knowing why neuroticism predicts such a wide variety of seemingly diverse outcomes should lead to improved understanding of commonalities among those outcomes and improved strategies for preventing them.

Specification, testing, and interpretation of gene-by-measured-environment interaction models in the presence of gene-environment correlation

Purcell (Twin Res 5:554-571, 2002) proposed a bivariate biometric model for testing and quantifying the interaction between latent genetic influences and measured environments in the presence of gene-environment correlation. Purcell's model extends the Cholesky model to include gene-environment interaction. We examine a number of closely related alternative models that do not involve gene-environment interaction but which may fit the data as well as Purcell's model. Because failure to consider these alternatives could lead to spurious detection of gene-environment interaction, we propose alternative models for testing gene-environment interaction in the presence of gene-environment correlation, including one based on the correlated factors model. In addition, we note mathematical errors in the calculation of effect size via variance components in Purcell's model. We propose a statistical method for deriving and interpreting variance decompositions that are true to the fitted model.

Neuroticism and Physical Disorders Among Adults in the Community: Results from the National Comorbidity Survey

To examine the association between neuroticism and physical disorders among adults in the United States, data were drawn from the National Comorbidity Survey (n = 5,877). Multiple logistic regression analyses were used to examine the relationship between neuroticism and physical disorders among adults in the community, adjusting for differences in demographic characteristics and comorbid mental disorders.Results indicated that neuroticism was associated with significantly elevated rates of a wide range of physical disorders, with the exception of stroke. After adjusting for differences in demographic characteristics and comorbid mental disorders, neuroticism was associated with increased odds of arthritis (OR = 1.5), diabetes (OR = 3.33), kidney/liver disease (OR = 2.56), stomach/gallbladder problems (OR = 2.27), and ulcer (OR = 3.23). Based on those findings, neuroticism appears to be a general predictor of a range of physical health problems among adults in the United States. Much of this association appears to be partially mediated by comorbid mental disorders, yet the association between neuroticism and arthritis, diabetes, kidney/liver disease, stomach problems, and ulcer persist even after adjusting for differences in demographic characteristics and comorbid mental disorders. Future studies that can examine the nature and mechanism of these linkages across the lifespan are needed next.