Racial Disparities in Depression and Life Satisfaction After Spinal Cord Injury: A Mediational Model

Gut Microbiota–Brain Axis as a Potential Modulator of Psychological Stress after Spinal Cord Injury

A growing body of evidence from preclinical and clinical studies has associated alterations of the gut microbiota–brain axis with the progression and development of a number of pathological conditions that also affect cognitive functions. Spinal cord injuries (SCIs) can be produced from traumatic and non-traumatic causes. It has been reported that SCIs are commonly associated with anxiety and depression-like symptoms, showing an incidence range between 11 and 30% after the injury. These psychological stress-related symptoms are associated with worse prognoses in SCIs and have been attributed to psychosocial stressors and losses of independence. Nevertheless, emotional and mental modifications after SCI could be related to changes in the volume of specific brain areas associated with information processing and emotions. Additionally, physiological modifications have been recognized as a predisposing factor for mental health depletion, including the development of gut dysbiosis. This condition of imbalance in microbiota composition has been shown to be associated with depression in clinical and pre-clinical models. Therefore, the understanding of the mechanisms underlying the relationship between SCIs, gut dysbiosis and psychological stress could contribute to the development of novel therapeutic strategies to improve SCI patients’ quality of life.

Mediating Effects of Pain Interference on the Relationships Between Pain Intensity and Probable Major Depression Among Participants With Spinal Cord Injury

OBJECTIVE

To evaluate whether pain interference mediates the relationship between pain intensity and probable major depression (PMD) among persons with spinal cord injury (SCI), accounting for differences in the frequency of prescription medication use and resilience.

DESIGN

Cross-sectional analysis using self-report assessment.

SETTING

Medical university in the Southeastern United States.

PARTICIPANTS

There were a total of 4670 participants (N=4670), all of whom had traumatic SCI of at least 1-year duration, identified from the Southeastern Regional SCI Model System and 2 state-based surveillance systems.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Patient Health Questionnaire-9 was used to define PMD. Covariates included demographic and injury characteristics, pain severity, pain interference, and resilience. Separate sets of multistage logistic regression analyses were conducted for 3 levels of prescription pain medication use (daily, occasional/weekly, none).

RESULTS

Pain intensity was related to a greater risk of PMD (odds ratio [OR]_{daily pain medication user}, 1.28; 95% confidence interval [CI], 1.21-1.35; OR_{occasional/weekly pain medication user}, 1.26; 95% CI, 1.16-1.36; OR_{nonpain medication user}, 1.44; 95% CI, 1.33-1.56), but this relationship disappeared after consideration of pain interference (OR_{daily pain medication user}, 0.97; 95% CI, 0.90-1.04; OR_{occasional/weekly pain medication user}, 0.94; 95% CI, 0.84-1.05; OR_{nonpain medication user}, 1.07; 95% CI, 0.95-1.20), which indicates pain interference was a mediator between pain intensity and PMD and there was no direct relationship between pain intensity and PMD. Resilience was protective of PMD in each model but was not a mediator.

CONCLUSIONS

Although pain intensity was associated with PMD, the relationship was mediated by pain interference. Resilience was an important protective factor. Therefore, clinicians should assess pain interference when screening for PMD and direct treatment at reducing pain interference. Building resilience may further reduce the risk of PMD.

Income Gradient in Renal Disease Mortality in the United States

Background

Non-communicable diseases and associated mortality follow a social gradient and chronic kidney disease is not an exception to this rule. Intermediate behavioral and medical factors that may explain such social gradients are, however, still unknown.

Objectives

Using nationally representative data in the United States, this study was conducted to investigate the mediating effect of medical and behavioral risk factors on the association between socioeconomic status (SES) and renal disease mortality.

Patients and methods

Americans’ Changing Lives Study (ACL), 1986–2011, is a 25-year nationally representative prospective cohort study. ACL followed 3,361 adults for up to 25 years. Income, education, and unemployment were the main predictors of interest. Death due to renal disease was the main outcome. Health behaviors (smoking, drinking, and exercise) and medical risk factors (diabetes, hypertension, and obesity) were the mediators. Cox proportional hazards models were used for data analysis.

Results

Higher income (HR = 0.75; 95% CI = 0.62–0.89) was associated with lower risk of death due to renal disease over the 25-year follow-up period. Although health behaviors and medical risk factors at baseline were also predictors of the outcome, they failed to explain the effect of income on death due to renal disease. That is, income was associated with death due to renal disease above and beyond all potential mediators including behavioral and medical risk factors.

Conclusion

Socioeconomic inequalities in the United States cause disparities in renal disease mortality; however, such differences are not due to health behaviors (smoking and drinking) and medical risk factors (hypertension and diabetes). To reduce disparities in renal disease mortality in the United States, policies should go beyond health behaviors and medical risk factors. While programs should help low-income individuals maintain exercise and avoid smoking, reduction of income disparities should be regarded as a strategy for reduction of disparities in renal disease mortality. By increasing minimum pay and minimizing the income gap, we may reduce disparities in renal disease mortality.

Diabetes, hypertension, obesity, and long-term risk of renal disease mortality: Racial and socioeconomic differences

AIMS/INTRODUCTION

Diabetes, hypertension, and obesity increase the risk of chronic kidney disease and associated mortality. Race and socioeconomic status (SES) differences in the effects of these risk factors are, however, still unknown. The current study aimed to investigate whether or not race and SES alter the effects of diabetes, hypertension, and obesity on mortality due to renal disease.

MATERIALS AND METHODS

Data came from the Americans' Changing Lives Study, 1986-2011, a nationally representative prospective cohort of adults with 25 years of follow up. The study included 3,361 adults aged 25 years and older who were followed for up to 25 years. The outcome was death from renal disease. Diabetes, hypertension, and obesity were the main predictors. Race and SES (education, income, and employment) were moderators. Health behaviors and health status at baseline were covariates. We used Cox proportional hazards models for data analysis.

RESULTS

In separate models, diabetes, hypertension, and obesity at baseline were associated with a higher risk of death from renal disease. From our SES indicators, education and income interacted with diabetes, hypertension, and obesity on death from renal disease. In a consistent pattern, diabetes, hypertension, and obesity showed stronger effects on the risk of death from renal disease among high-SES groups compared with low-SES individuals. Race and employment did not alter the effects of diabetes, hypertension and obesity on the risk of death from renal disease.

CONCLUSIONS

Social groups differ in how diabetes, hypertension, and obesity influence health outcomes over long-term periods. Elimination of disparities in renal disease mortality in the USA requires understanding of the complex and non-linear effects of socioeconomic and medical risk factors on health outcomes. Multidisciplinary programs and policies are required to reduce social inequality in renal disease burden caused by diabetes, hypertension, and obesity.

Depressive symptomatology after spinal cord injury: A multi-center investigation of multiple racial-ethnic groups

OBJECTIVE

To identify (1) racial-ethnic differences in depressive symptomatology after spinal cord injury (SCI) and (2) the relationship of multiple additional factors to depressive symptoms, including health behaviors, employment, fatigue, and pain interference.

DESIGN

Cross-sectional Setting: Data were collected at 3 specialty hospitals in different regions of the USA (Southeastern, Mountain, Western).

PARTICIPANTS

Participants (N = 1,063) were identified from outpatient records of the 3 hospitals with oversampling of racial-ethnic minority groups.

INTERVENTIONS

N/A Main Outcome Measure(s): The outcome, depressive symptomatology, was measured by the Older Adult Health and Mood Questionnaire (OAHMQ). Participant demographic and injury characteristics were measured as statistical controls, as well as other variables including health behavior factors, depression/stress relief medication usage, fatigue, and pain interference. The multivariate analyses were developed using OLS regression models and logistic regression models.

RESULTS

Employment was protective for depressive symptomatology, whereas fatigue, pain interference, and binge drinking were risk factors for higher OAHMQ scores. Although there were no bivariate racial-ethnic differences in depressive symptoms, fatigue and pain interference had suppression effects on the relationship between race-ethnicity and depressive symptomatology. After controlling for fatigue and pain interference, Hispanic participants had significantly lower OAHMQ scores and lower odds of probable major depression (PMD) than non-Hispanic Whites and Blacks.

CONCLUSIONS

Fatigue and pain interference are associated with both race-ethnicity and depressive symptomatology. Assuming the same level of fatigue and pain interference, Hispanics will have a lower risk of depressive symptoms than non-Hispanic Whites and Blacks.

Distal, intermediate, and proximal mediators of racial disparities in renal disease mortality in the United States

Background: Kidney failure and associated mortality is one of the major components of racial disparities in the United States.

Objectives: The current study aimed to investigate the role of distal (socioeconomic status, SES), intermediate (chronic medical diseases), and proximal (health behaviors) factors that may explain Black-White disparities in mortality due to renal diseases.

Patients and Methods: This is a nationally representative prospective cohort with 25 years of follow up. Data came from the Americans’ Changing Lives (ACL) study, 1986 to 2011. The study included 3361 Black (n = 1156) or White (n = 2205) adults who were followed for up to 25 years. Race was the main predictor and death due to renal disease was the outcome. SES, chronic medical disease (diabetes, hypertension, obesity), and health behaviors (smoking, drinking, and exercise) at baseline were potential mediators. We used Cox proportional hazards models for data analysis.

Results: In age and gender adjusted models, Blacks had higher risk of death due to renal disease over the follow up period. Separate models suggested that SES, health behaviors and chronic medical disease fully explained the effect of race on renal disease mortality.

Conclusions: Black-White disparities in rate of death due to renal diseases in the United States are not genuine but secondary to racial differences in income, health behaviors, hypertension, and diabetes. As distal, intermediate, and proximal factors contribute to racial disparities in renal disease mortality, elimination of such disparities requires a wide range of policies and programs that target income, medical conditions, and health behaviors.