Investigating the relationship between socioeconomic status and health across the life-course and among people with chronic disease

Socioeconomic inequalities in health are a persistent and pervasive social injustice, with lower socioeconomic status (SES) being associated with poorer health outcomes and higher mortality in countries across the world. Despite some important progress, in many areas socioeconomic inequalities in health have persisted or even worsened over time. One of the barriers to progress on socioeconomic inequalities in health is our incomplete understanding of the complex relationship between SES and health, including their dynamic and bidirectional interactions across the life-course, and how their relationship varies across different populations, countries, socioeconomic exposures and health outcomes. The overarching aim of the program of work presented in this thesis was to develop a better understanding of the nature and underlying processes of socioeconomic inequalities in health. Such information can be used to inform the timing, targeting and nature of health equity-focused interventions. The thesis aimed to contribute to two broad areas of research need related to socioeconomic inequalities in health. First, it aimed to investigate the dynamic and bidirectional associations between SES and health across the life-course, using principles and methods from the life-course approach to health. Second, it aimed to explore socioeconomic inequalities in health among people with chronic disease, using chronic kidney disease (CKD) as an example

Effects of omega-3 polyunsaturated fatty acid intake in patients with chronic kidney disease: Systematic review and meta-analysis of randomized controlled trials

Background & aims: Dietary and supplemental long chain omega-3 polyunsaturated fatty acids (n-3 PUFA) have shown vascular benefits for the general population, but effects among people with chronic kidney disease (CKD) are largely uncertain. We aimed to evaluate the effects of n-3 PUFA intake among patients with CKD. Methods: We searched MEDLINE, Embase, and CENTRAL through January 12, 2018. Eligible studies were randomized controlled trials evaluating n-3 PUFA intake (supplementation or dietary) compared with placebo, standard care, or other treatment, on cardiovascular and all-cause mortality, end stage kidney disease (ESKD), acute transplant rejection, and allograft loss. Risks of bias and evidence certainty were assessed using Cochrane and Grading of Recommendations Assessment, Development and Evaluation processes. Results: Sixty trials (4129 participants) were eligible, all of supplementation, with a median follow-up of 6 months. Low to very low certainty evidence suggested that n-3 PUFA supplementation reduced cardiovascular death for participants on hemodialysis (39 events; relative risk (RR) 0.45, 95% confidence interval (CI) 0.23–0.89), prevented ESKD (29 events; RR 0.30, CI 0.09–0.98) in participants with CKD not receiving renal replacement therapy, and made little or no difference in all-cause mortality (215 events; RR 1.05, CI 0.84–1.33), acute transplant rejection (188 events; RR 0.98, CI 0.80–1.21) or allograft loss (39 events; RR 0.98, CI 0.54–1.81]). Risk of bleeding (44 events; RR 1.40, CI 0.78–2.49) and gastrointestinal side-effects (103 events; RR 1.14, CI 0.79–1.67) were uncertain. Conclusions: n-3 PUFA supplementation may reduce cardiovascular mortality in patients on hemodialysis but it is uncertain whether supplementation prevents mortality or ESKD in patients with CKD

Social cognition deficits and psychopathic traits in young people seeking mental health treatment.

Antisocial behaviours and psychopathic traits place an individual at risk for criminality, mental illness, substance dependence, and psychosocial dysfunction. Social cognition deficits appear to be associated with psychopathic traits and are believed to contribute to interpersonal dysfunction. Most research investigating the relationship of these traits with social cognition has been conducted either in children or adult forensic settings. We investigated whether psychopathic traits were associated with social cognition in 91 young people presenting for mental healthcare (aged between 15 and 25 years). Participants completed symptom severity measures, neuropsychological tests, the Reading the Mind in the Eyes Test of social cognition (RMET), and the Antisocial Process Screening Device (APSD) to assess psychopathic personality traits. Correlation analyses showed poorer social cognition was associated with greater psychopathic traits (r = -.36, p = .01). Interestingly, social cognition performance predicted unique variance in concurrent psychopathic personality traits above gender, IQ sustained attention, and working memory performance. These findings suggest that social cognitive impairments are associated with psychopathic tendencies in young people presenting for community mental healthcare. Research is needed to establish the directionality of this relationship and to determine whether social cognition training is an effective treatment amongst young people with psychopathic tendencies

Comparison of resting heart rate variability between males and females with social anxiety, compared to controls, across mean heart rate (row 1), as well as time (row 2), frequency (row 3), and non-linear (row 4) domains.

<p><i>Note.</i> All variables are log-transformed (base 10), except for A (which depicts untransformed beats per minute). Error bars depict standard error of the mean. Significance taken from multivariate analysis of variance with group and gender entered as between subjects variables. Significance tests were not conducted on untransformed mean heart rate. MHR = mean heart rate, beats/min, SDNN = standard deviation of all R-R intervals, RMSSD = square root of mean squared differences of successive R-R intervals, LF = low frequency, HF = high frequency, PCSD1 =  standard deviation of the Poincaré plot perpendicular to the line of identity, DFAα1 =  detrended fluctuation analysis of the short-fluctuation slope. *<i>p</i><.05, **<i>p</i><.01.</p

Participant characteristics.

<p><i>Note.</i> Numbers depict means (and standard deviations) or numbers in each category. Significance values taken from main and interaction ANOVA tests or chi-squared tests. BMI = Body Mass Index in kg/m²; SPAI = Social Phobia Anxiety Inventory, 23-item version, total score summing social anxiety and agoraphobia subscales; DASS = Depression, Anxiety, Stress scales, 21-item version; AUDIT-C = Alcohol Use Disorder Identification Test, consumption subscale; MET = estimate of metabolic energy expenditure in minutes per week. ^aSAD group <i>n</i> = 51 ^bSAD group <i>n</i> = 50 ^cSAD group <i>n</i> = 52 ^dSAD group <i>n</i> = 48, Control group <i>n</i> = 51.</p

Log–transformed HRV between groups.

<p><i>Note.</i> Variables are log-transformed (base 10) and depict means (standard deviations). Significance values taken from multivariate analysis of variance with group and gender entered as between subjects variables. MHR = mean heart rate, beats/min, SDNN = standard deviation of all R-R intervals, RMSSD = square root of mean squared differences of successive R-R intervals, LF = low frequency, HF = high frequency, PCSD1 =  standard deviation of the Poincaré plot perpendicular to the line of identity, DFAα1 =  detrended fluctuation analysis of the short-fluctuation slope.</p

Bivariate correlation coefficients between HRV and symptom severity measures.

<p><i>Note</i>. HRV measures are log transformed. SPAI = Social Phobia Anxiety Inventory, 23-item version; DASS = Depression, Anxiety, and Stress Scale; LSAS = Liebowitz Social Anxiety Scale; SIAS = Social Interaction Anxiety Scale; SPS = Social Phobia Scale; AUDIT = Alcohol Use Disorders Identification Test; k10 =  Kessler psychological distress scale, 10-items.</p>*<p><i>p</i><.05,</p>**<p><i>p</i><.01 (two-tailed).</p>a<p><i>n</i> = 51;</p>b<p><i>n</i> = 50;</p>c<p><i>n</i> = 49;</p>d<p><i>n</i> = 52.</p

Hierarchical Regression Predicting APSD Score from Gender, IQ, RVP-A, SSP, and RMET Score.

<p><i>Note.</i> *<i>p</i><0.05.</p

Symptom Severity Scores Across Quartiles of APSD Score.

<p>Note.</p>a<p>n = 24.</p>b<p>n = 24.</p>c<p>n = 22.</p>d<p>n = 21.</p>e<p>n = 91.</p