Optimal design strategies for sibling studies with binary exposures

Cardiovascular Risk Factor Disparities in Adult Survivors of Childhood Cancer Compared With the General Population

Background

It is unknown whether a history of childhood cancer modifies the established disparities in cardiovascular risk factors (CVRFs) observed in the general population.

Objectives

We sought to determine if disparities in CVRFs by race/ethnicity are similar among childhood cancer survivors compared with the general population.

Methods

The Childhood Cancer Survivor Study (CCSS) is a retrospective cohort with a longitudinal follow-up of 24,084 5-year survivors diagnosed between 1970 and 1999. Multivariable piecewise exponential regression estimated incidence rate ratios (IRRs) for hypertension, hyperlipidemia, diabetes, obesity, and ≥2 CVRFs by race/ethnicity. The CCSS sibling cohort and the National Health and Nutrition Examination Survey cohort were used to compare the sociodemographic-adjusted IRRs for same-race/same-ethnicity disparities.

Results

Non-Hispanic Black (NHB) (n = 1,092) and Hispanic (n = 1,405) survivors compared with non-Hispanic White (NHW) (n = 13,960) survivors reported a higher cumulative incidence of diabetes (8.4%, 9.7%, and 5.1%, respectively); obesity (47.2%, 48.9%, and 30.2%, respectively); multiple CVRFs (17.7%, 16.6%, and 12.3%, respectively); and, for NHB survivors, hypertension (19.5%, 13.6%, and 14.3%, respectively) by 40 years of age (P < 0.001). Controlling for sociodemographic and treatment factors compared with NHW survivors, IRRs for NHB were increased for hypertension (IRR: 1.4; 95% CI: 1.1-1.8), obesity (IRR: 1.7; 95% CI: 1.4-2.1), and multiple CVRFs (IRR: 1.6; 95% CI: 1.2-2.1). IRRs for Hispanic survivors were increased for diabetes (IRR: 1.8; 95% CI: 1.2-2.6) and obesity (IRR: 1.4; 95% CI: 1.2-1.7). The pattern of IRRs for CVRF differences was similar among CCSS sibling and National Health and Nutrition Examination Survey cohorts.

Conclusions

The higher burden of CVRFs among NHB and Hispanic survivors compared with NHW survivors was similar to the general population. The promotion of cardiovascular health equity is critical in this high-risk population.

Prospectively Predicting Adult Depressive Symptoms from Adolescent Peer Dysfunction: a Sibling Comparison Study

Previous studies have shown that peer dysfunction in adolescence predicts depression in adulthood, even when controlling for certain individual- and/or family-level characteristics. However, these studies have not controlled for numerous potential familial confounders, precluding causal inferences. The present study therefore used a sibling comparison design (i.e., comparing siblings within families) to test whether peer dysfunction (e.g., lack of friendships, victimization) in adolescence continues to predict depression in adulthood after accounting for unmeasured familial confounds and individual characteristics in adolescence. Participants’ (N = 85) dysfunction with peers was assessed in adolescence (M_age = 13.21, SD = 3.47) by self- and parent-report, and adult depressive symptoms were assessed up to five times, up to 38 years later. Multilevel modeling was used to examine the effect of adolescent peer dysfunction on adult depressive symptoms after adjusting for familial confounds and/or individual characteristics in adolescence (e.g., baseline depressive symptoms, dysfunctional relations with siblings/parents). Both self-reported (b = 1.28, p < 0.001) and parent-reported (b = 0.56, p = 0.032) adolescent peer dysfunction were associated with greater depressive symptom severity in adulthood in unadjusted models. Self-reported (but not parent-reported) adolescent peer dysfunction continued to predict adult depressive symptoms after controlling for familial confounding and measured covariates such as adolescent depressive symptoms and relations with siblings and parents (b = 1.06, p = 0.035). Although confidence intervals were wide and the potentially confounding effects of numerous individual-level factors were not ruled out, these findings provide preliminary evidence that perceived peer dysfunction in adolescence may be an unconfounded risk factor for depressive symptoms in adulthood.

Whole-Genome Sequencing of Finnish Type 1 Diabetic Siblings Discordant for Kidney Disease Reveals DNA Variants associated with Diabetic Nephropathy

BACKGROUND

Several genetic susceptibility loci associated with diabetic nephropathy have been documented, but no causative variants implying novel pathogenetic mechanisms have been elucidated.

METHODS

We carried out whole-genome sequencing of a discovery cohort of Finnish siblings with type 1 diabetes who were discordant for the presence (case) or absence (control) of diabetic nephropathy. Controls had diabetes without complications for 15-37 years. We analyzed and annotated variants at genome, gene, and single-nucleotide variant levels. We then replicated the associated variants, genes, and regions in a replication cohort from the Finnish Diabetic Nephropathy study that included 3531 unrelated Finns with type 1 diabetes.

RESULTS

We observed protein-altering variants and an enrichment of variants in regions associated with the presence or absence of diabetic nephropathy. The replication cohort confirmed variants in both regulatory and protein-coding regions. We also observed that diabetic nephropathy-associated variants, when clustered at the gene level, are enriched in a core protein-interaction network representing proteins essential for podocyte function. These genes include protein kinases (protein kinase C isoforms ε and ι) and protein tyrosine kinase 2.

CONCLUSIONS

Our comprehensive analysis of a diabetic nephropathy cohort of siblings with type 1 diabetes who were discordant for kidney disease points to variants and genes that are potentially causative or protective for diabetic nephropathy. This includes variants in two isoforms of the protein kinase C family not previously linked to diabetic nephropathy, adding support to previous hypotheses that the protein kinase C family members play a role in diabetic nephropathy and might be attractive therapeutic targets.

The association between depressive mood and ischemic heart disease: a twin study

OBJECTIVE

Individuals with mood disorders have increased risk of cardiovascular disease. The aims of this study were to evaluate if the risk of cardiovascular disease in individuals with mood disorder could be explained by shared genetic and early environmental factors.

METHODS

We included 6714 Danish middle and old aged twins from two large population-based studies. Cox proportional hazards regression was used to perform individual-level and intra-pair analyses of the association between self-reported depression symptomatology scores and register-based diagnoses of ischemic heart disease.

RESULTS

Higher depression symptomatology scores (both total, affective, and somatic) were associated with higher incidence of ischemic heart disease after multivariable adjustment in individual-level analyses. In intra-pair analyses, this association was similar but with slightly larger confidence intervals. There was no interaction with gender and no major differences between mono- or dizygotic twins. Within twin pairs, the twin scoring highest on depressive symptoms developed ischemic heart disease more often or earlier than the lower scoring twin. A sensitivity analysis including a 2-year time lag of depression symptomatology to limit the risk of reverse causality showed similar results.

CONCLUSION

Genetic factors and early life environment do not seem to explain the association between depressive mood and ischemic heart disease.

Suicide Attempts and Completions among Mothers Whose Children Were Taken into Care by Child Protection Services: A Cohort Study Using Linkable Administrative Data

OBJECTIVE

The objective of this study is to examine suicide attempts and completions among mothers who had a child taken into care by child protection services (CPS). These mothers were compared with their biological sisters who did not have a child taken into care and with mothers who received services from CPS but did not have a child taken into care.

METHODS

A retrospective cohort of mothers whose first child was born in Manitoba, Canada, between April 1, 1992, and March 31, 2015, is used. Rates among discordant biological sisters (1872 families) were compared using fixed-effects Poisson regression models, and mothers involved with CPS (children in care [ n = 1872] and received services [ n = 9590]) were compared using a Poisson regression model.

RESULTS

Compared with their biological sisters and mothers who received services, the adjusted incidence rate ratio (aIRR) of death by suicide was greater among mothers whose child was taken into care by CPS (aIRR = 4.46 [95% confidence interval (CI), 1.39-14.33] and ARR = 3.45 [95% CI, 1.61-7.40], respectively). Incidence rates of suicide attempts were higher among mothers with a child taken into care compared with their sisters (aIRR = 2.15; 95% CI, 1.40-3.30) and mothers receiving services (aIRR = 2.82; 95% CI, 2.03-3.92).

CONCLUSIONS

Mothers who had a child taken into care had significantly higher rates of suicide attempts and completions. When children are taken into care, physician and social workers should inquire about maternal suicidal behaviour and provide appropriate mental health.

Risk of hospitalization among survivors of childhood and adolescent acute lymphoblastic leukemia compared to siblings and a general population sample

BACKGROUND

Acute Lymphoblastic Leukemia (ALL) has a high survival rate, but cancer-related late effects in the early post-treatment years need documentation. Hospitalizations are an indicator of the burden of late effects. We identify rates and risk factors for hospitalization from five to ten years after diagnosis for childhood and adolescent ALL survivors compared to siblings and a matched population sample.

METHODS

176 ALL survivors were diagnosed at ≤22 years between 1998 and 2008 and treated at an Intermountain Healthcare facility. The Utah Population Database identified siblings, an age- and sex-matched sample of the Utah population, and statewide inpatient hospital discharges. Sex- and birth year-adjusted Poisson models with Generalized Estimating Equations and robust standard errors calculated rates and rate ratios. Cox proportional hazards models identified demographic and clinical risk factors for hospitalizations among survivors.

RESULTS

Hospitalization rates for survivors (Rate:3.76, 95% CI=2.22-6.36) were higher than siblings (Rate:2.69, 95% CI=1.01-7.18) and the population sample (Rate:1.87, 95% CI=1.13-3.09). Compared to siblings and population comparisons, rate ratios (RR) were significantly higher for survivors diagnosed between age 6 and 22 years (RR:2.87, 95% CI=1.03-7.97 vs siblings; RR:2.66, 95% CI=1.17-6.04 vs population comparisons). Rate ratios for diagnosis between 2004 and 2008 were significantly higher compared to the population sample (RR:4.29, 95% CI=1.49, 12.32), but not siblings (RR:2.73, 95% CI=0.54, 13.68). Survivors originally diagnosed with high-risk ALL did not have a significantly higher risk than siblings or population comparators. However, high-risk ALL survivors (Hazard ratio [HR]:3.36, 95% CI=1.33-8.45) and survivors diagnosed from 2004 to 2008 (HR:9.48, 95% CI=1.93-46.59) had the highest risk compared to their survivor counterparts.

CONCLUSIONS

Five to ten years after diagnosis is a sensitive time period for hospitalizations in the ALL population. Survivors of childhood ALL require better long-term surveillance.