Birth Order, Sibship Size, Childhood Environment and Immune-Related Disorders, and Risk of Lymphoma in Lymphoid Cancer Families

A Pregnancy and Childhood Epigenetics Consortium (PACE) meta-analysis highlights potential relationships between birth order and neonatal blood DNA methylation

Higher birth order is associated with altered risk of many disease states. Changes in placentation and exposures to in utero growth factors with successive pregnancies may impact later life disease risk via persistent DNA methylation alterations. We investigated birth order with Illumina DNA methylation array data in each of 16 birth cohorts (8164 newborns) with European, African, and Latino ancestries from the Pregnancy and Childhood Epigenetics Consortium. Meta-analyzed data demonstrated systematic DNA methylation variation in 341 CpGs (FDR adjusted P < 0.05) and 1107 regions. Forty CpGs were located within known quantitative trait loci for gene expression traits in blood, and trait enrichment analysis suggested a strong association with immune-related, transcriptional control, and blood pressure regulation phenotypes. Decreasing fertility rates worldwide with the concomitant increased proportion of first-born children highlights a potential reflection of birth order-related epigenomic states on changing disease incidence trends.

Gene and pathway based burden analyses in familial lymphoid cancer cases: Rare variants in immune pathway genes

Genome-wide association studies have revealed common genetic variants with small effect sizes associated with diverse lymphoid cancers. Family studies have uncovered rare variants with high effect sizes. However, these variants explain only a portion of the heritability of these cancers. Some of the missing heritability may be attributable to rare variants with small effect sizes. We aim to identify rare germline variants associated with familial lymphoid cancers using exome sequencing. One case per family was selected from 39 lymphoid cancer families based on early onset of disease or rarity of subtype. Control data was from Non-Finnish Europeans in gnomAD exomes (N = 56,885) or ExAC (N = 33,370). Gene and pathway-based burden tests for rare variants were performed using TRAPD. Five putatively pathogenic germline variants were found in four genes: INTU, PEX7, EHHADH, and ASXL1. Pathway-based association tests identified the innate and adaptive immune systems, peroxisomal pathway and olfactory receptor pathway as associated with lymphoid cancers in familial cases. Our results suggest that rare inherited defects in the genes involved in immune system and peroxisomal pathway may predispose individuals to lymphoid cancers.

Bereavement Among Adult Siblings: An Examination of Health Services Utilization and Mental Health Outcomes

We aimed to examine the association of young and middle-aged sibling bereavement with use of health services and risk of developing mental health disorders over 24 months before and after sibling's death. All persons aged 18-56 years who died of illness/natural causes between 2009 and 2016 were identified in the Danish Register of Causes of Death. The study sample included 31,842 bereaved siblings and 31,842 age- and sex-matched controls. Overall, the largest effect was observed for increased use of psychological services: For women, the peak was observed 4-6 months after the death (odds ratio (OR) = 3.31, 95% confidence interval (CI): 2.85, 3.85) and for men in the first 3 months after the death (OR = 2.63, 95% CI: 2.06, 3.36). The peak of being diagnosed in a hospital setting with any mental disorder for women was observed in the period 13-15 months after sibling death (OR = 1.52, 95% CI: 1.11, 2.07) and for men in the first 3 months after the death (OR = 1.75, 95% CI: 1.32, 2.32). Young and middle-aged adults who experienced the death of a sibling are more likely to use health services and are at risk of poorer mental health outcomes. During the bereavement process, young and middle-aged siblings are especially in need of mental health support, such as professional psychological counseling.