Stratified genetic analysis reveals sex differences in MPO-ANCA-associated vasculitis.

OBJECTIVE: To identify and genetically characterize subgroups of patients with ANCA-associated vasculitides (AAV) based on sex and ANCA subtype. METHODS: A previously established SNP dataset derived from DNA sequencing of 1853 genes and genotyping of 1088 Scandinavian cases with AAV and 1589 controls was stratified for sex and ANCA subtype and analysed for association with five top AAV SNPs. rs9274619, a lead variant at the HLA-DQB1/HLA-DQA2 locus previously associated with AAV positive for myeloperoxidase (MPO)-ANCA, was analysed for association with the cumulative disease involvement of ten different organ systems. RESULTS: rs9274619 showed a significantly stronger association to MPO-ANCA-positive females than males [P = 2.0 × 10-4, OR = 2.3 (95% CI 1.5, 3.5)], whereas proteinase 3 (PR3)-ANCA-associated variants rs1042335, rs9277341 (HLA-DPB1/A1) and rs28929474 (SERPINA1) were equally associated with females and males with PR3-ANCA. In MPO-ANCA-positive cases, carriers of the rs9274619 risk allele were more prone to disease engagement of eyes [P = 0.021, OR = 11 (95% CI 2.2, 205)] but less prone to pulmonary involvement [P = 0.026, OR = 0.52 (95% CI 0.30, 0.92)]. Moreover, AAV with both MPO-ANCA and PR3-ANCA was associated with the PR3-ANCA lead SNP rs1042335 [P = 0.0015, OR = 0.091 (95% CI 0.0022, 0.55)] but not with rs9274619. CONCLUSIONS: Females and males with MPO-ANCA-positive AAV differ in genetic predisposition to disease, suggesting at least partially distinct disease mechanisms between the sexes. Double ANCA-positive AAV cases are genetically similar to PR3-ANCA-positive cases, providing clues to the clinical follow-up and treatment of these patients.

Integration of small RNAs from plasma and cerebrospinal fluid for classification of multiple sclerosis.

Multiple Sclerosis (MS) is an autoimmune, neurological disease, commonly presenting with a relapsing-remitting form, that later converts to a secondary progressive stage, referred to as RRMS and SPMS, respectively. Early treatment slows disease progression, hence, accurate and early diagnosis is crucial. Recent advances in large-scale data processing and analysis have progressed molecular biomarker development. Here, we focus on small RNA data derived from cell-free cerebrospinal fluid (CSF), cerebrospinal fluid cells, plasma and peripheral blood mononuclear cells as well as CSF cell methylome data, from people with RRMS (n = 20), clinically/radiologically isolated syndrome (CIS/RIS, n = 2) and neurological disease controls (n = 14). We applied multiple co-inertia analysis (MCIA), an unsupervised and thereby unbiased, multivariate method for simultaneous data integration and found that the top latent variable classifies RRMS status with an Area Under the Receiver Operating Characteristics (AUROC) score of 0.82. Variable selection based on Lasso regression reduced features to 44, derived from the small RNAs from plasma (20), CSF cells (8) and cell-free CSF (16), with a marginal reduction in AUROC to 0.79. Samples from SPMS patients (n = 6) were subsequently projected on the latent space and differed significantly from RRMS and controls. On contrary, we found no differences between relapse and remission or between inflammatory and non-inflammatory disease controls, suggesting that the latent variable is not prone to inflammatory signals alone, but could be MS-specific. Hence, we here showcase that integration of small RNAs from plasma and CSF can be utilized to distinguish RRMS from SPMS and neurological disease controls.

Contribution of rare whole-genome sequencing variants to plasma protein levels and the missing heritability.

Despite the success of genome-wide association studies, much of the genetic contribution to complex traits remains unexplained. Here, we analyse high coverage whole-genome sequencing data, to evaluate the contribution of rare genetic variants to 414 plasma proteins. The frequency distribution of genetic variants is skewed towards the rare spectrum, and damaging variants are more often rare. We estimate that less than 4.3% of the narrow-sense heritability is expected to be explained by rare variants in our cohort. Using a gene-based approach, we identify Cis-associations for 237 of the proteins, which is slightly more compared to a GWAS (N = 213), and we identify 34 associated loci in Trans. Several associations are driven by rare variants, which have larger effects, on average. We therefore conclude that rare variants could be of importance for precision medicine applications, but have a more limited contribution to the missing heritability of complex diseases.

Identification and functional characterization of a novel susceptibility locus for small vessel vasculitis with MPO-ANCA.

OBJECTIVE: To identify and characterize genetic loci associated with the risk of developing ANCA-associated vasculitides (AAV). METHODS: Genetic association analyses were performed after Illumina sequencing of 1853 genes and subsequent replication with genotyping of selected single nucleotide polymorphisms in a total cohort of 1110 Scandinavian cases with granulomatosis with polyangiitis or microscopic polyangiitis, and 1589 controls. A novel AAV-associated single nucleotide polymorphism was analysed for allele-specific effects on gene expression using luciferase reporter assay. RESULTS: PR3-ANCA+ AAV was significantly associated with two independent loci in the HLA-DPB1/HLA-DPA1 region [rs1042335, P = 6.3 × 10-61, odds ratio (OR) 0.10; rs9277341, P = 1.5 × 10-44, OR 0.22] and with rs28929474 in the SERPINA1 gene (P = 2.7 × 10-10, OR 2.9). MPO-ANCA+ AAV was significantly associated with the HLA-DQB1/HLA-DQA2 locus (rs9274619, P = 5.4 × 10-25, OR 3.7) and with a rare variant in the BACH2 gene (rs78275221, P = 7.9 × 10-7, OR 3.0), the latter a novel susceptibility locus for MPO-ANCA+ granulomatosis with polyangiitis/microscopic polyangiitis. The rs78275221-A risk allele reduced luciferase gene expression in endothelial cells, specifically, as compared with the non-risk allele. CONCLUSION: We identified a novel susceptibility locus for MPO-ANCA+ AAV and propose that the associated variant is of mechanistic importance, exerting a regulatory function on gene expression in specific cell types.

Whole-genome resequencing confirms reproductive isolation between sympatric demes of brown trout (Salmo trutta) detected with allozymes.

The sympatric existence of genetically distinguishable populations of the same species remains a puzzle in ecology. Coexisting salmonid fish populations are known from over 100 freshwater lakes. Most studies of sympatric populations have used limited numbers of genetic markers making it unclear if genetic divergence involves certain parts of the genome. We returned to the first reported case of salmonid sympatry, initially detected through contrasting homozygosity at a single allozyme locus (coding for lactate dehydrogenase A) in brown trout in the small Lakes Bunnersjöarna, Sweden. First, we verified the existence of the two coexisting demes using a 96-SNP fluidigm array. We then applied whole-genome resequencing of pooled DNA to explore genome-wide diversity within and between these demes; nucleotide diversity was higher in deme I than in deme II. Strong genetic divergence is observed with genome-wide FST  ≈ 0.2. Compared with data from populations of similar small lakes, this divergence is of similar magnitude as that between reproductively isolated populations. Individual whole-genome resequencing of two individuals per deme suggests higher inbreeding in deme II versus deme I, indicating different degree of isolation. We located two gene-copies for LDH-A and found divergence between demes in a regulatory section of one of these genes. However, we did not find a perfect fit between the sequence data and previous allozyme results, and this will require further research. Our data demonstrates genome-wide divergence governed mostly by genetic drift but also by diversifying selection in coexisting populations. This type of hidden biodiversity needs consideration in conservation management.

Small noncoding RNA profiling across cellular and biofluid compartments and their implications for multiple sclerosis immunopathology.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease affecting the central nervous system (CNS). Small non-coding RNAs (sncRNAs) and, in particular, microRNAs (miRNAs) have frequently been associated with MS. Here, we performed a comprehensive analysis of all classes of sncRNAs in matching samples of peripheral blood mononuclear cells (PBMCs), plasma, cerebrospinal fluid (CSF) cells, and cell-free CSF from relapsing-remitting (RRMS, n = 12 in relapse and n = 11 in remission) patients, secondary progressive (SPMS, n = 6) MS patients, and noninflammatory and inflammatory neurological disease controls (NINDC, n = 11; INDC, n = 5). We show widespread changes in miRNAs and sncRNA-derived fragments of small nuclear, nucleolar, and transfer RNAs. In CSF cells, 133 out of 133 and 115 out of 117 differentially expressed sncRNAs were increased in RRMS relapse compared to remission and RRMS compared to NINDC, respectively. In contrast, 65 out of 67 differentially expressed PBMC sncRNAs were decreased in RRMS compared to NINDC. The striking contrast between the periphery and CNS suggests that sncRNA-mediated mechanisms, including alternative splicing, RNA degradation, and mRNA translation, regulate the transcriptome of pathogenic cells primarily in the CNS target organ.

Endophilin A2 deficiency protects rodents from autoimmune arthritis by modulating T cell activation.

The introduction of the CTLA-4 recombinant fusion protein has demonstrated therapeutic effects by selectively modulating T-cell activation in rheumatoid arthritis. Here we show, using a forward genetic approach, that a mutation in the SH3gl1 gene encoding the endocytic protein Endophilin A2 is associated with the development of arthritis in rodents. Defective expression of SH3gl1 affects T cell effector functions and alters the activation threshold of autoreactive T cells, thereby leading to complete protection from chronic autoimmune inflammatory disease in both mice and rats. We further show that SH3GL1 regulates human T cell signaling and T cell receptor internalization, and its expression is upregulated in rheumatoid arthritis patients. Collectively our data identify SH3GL1 as a key regulator of T cell activation, and as a potential target for treatment of autoimmune diseases.

Cognitive Distortions as Trauma-Specific Irrational Beliefs Among Burn Patients.

Burn injuries are most certainly stressful events, particularly when permanent disfigurement is a result. This situation can lead to the onset of irrational beliefs which can in turn lead to long-term psychological problems such as depression, anxiety, shame, guilt, posttraumatic stress, etc. The objective of this study is to explore the irrational beliefs among burn patients and its correlates in an Iranian sample. This cross-sectional study included 329 patients who had experienced disfigurement, as result of burn injuries. In order to assess irrational beliefs, a Scale for Irrational Thoughts after Burning was used. To identify correlated variables with irrational beliefs, both bivariate and multivariate analysis methods were conducted. In multivariate linear regression, forward strategy was used for building the model. The results of bivariate analysis showed that the location of the burn on bodies (body parts generally exposed in social environment or parts culturally perceived as sensitive areas of body), marital status, urbanities, age group, geographical areas, etiology of burning, and intent of injury had significant relationships with irrational beliefs (P < .05). Using forward linear regression, gender, marital status, geographical areas, etiology of burning, body burn by location (body parts generally exposed in social environment or parts culturally perceived as sensitive areas of body), and intent of injury had significant correlation with irrational beliefs. The models predicted 15.5% (P < .001) of irrational beliefs. Considering to irrational beliefs and development of facilities for screening is necessary. Moreover, consultation with mental health experts after burn injuries is highly recommended.

Switched On: How the Timing of Aversive Content in Traffic Safety Videos Impact Psychophysiological Indicators of Message Processing.

This study investigates how timing of the introduction of unpleasant emotional tone in a traffic safety video impacts the intensity of the viewer's emotional experience. Traffic safety advertising is a multi-million-dollar business in the United States. In many instances, 30-60 s ads are produced to raise awareness of the consequences of unsafe behaviors with the expectation that simply providing information will motivate safer behaviors. Producing videos intended to generate behavior change requires a complex understanding of what motivates behavior. Behavior change theory, neuroscience, and psychophysiology all provide guidance to improve the persuasive power of traffic safety videos. This study consisted of a 3 (message tone) × 3 (video) × 4 (order) repeated measures within subjects designed experiment. Participants (N = 75) were 20-30-year-old men who were shown nine traffic safety videos. Arousal intensity, attention, and negative emotion were tracked with the psychophysiological measures of skin conductance (measuring intensity of arousal), heart rate (measuring attention paid during the video), and corrugator muscle activation (measuring the negative emotional experience). Videos with three different aversive tones were used, low, high, and videos in which the tone switched from low to high aversive. Aversive tone is defined as stimuli that motivate a desire to escape or avoid something like death or pain. All videos were designed to prevent motor vehicle crashes. The results obtained from this study indicate that when attempting to persuade males aged 20-30 to practice safer driving behaviors, switched message tone appears to be the most effective message design in terms the intensity of emotional arousal and maintenance of attention.

Community-level football injury epidemiology: traumatic injuries treated at Swedish emergency medical facilities.

Background: Despite the popularity of the sport, few studies have investigated community-level football injury patterns. This study examines football injuries treated at emergency medical facilities using data from three Swedish counties. Methods: An open-cohort design was used based on residents aged 0-59 years in three Swedish counties (pop. 645 520). Data were collected from emergency medical facilities in the study counties between 1 January 2007 and 31 December 2010. Injury frequencies and proportions for age groups stratified by sex were calculated with 95% confidence intervals (95% CIs) and displayed per diagnostic group and body location. Results: Each year, more than 1/200 person aged 0-59 years sustained at least one injury during football play that required emergency medical care. The highest injury incidence was observed among adolescent boys [2009 injuries per 100 000 population years (95% CI 1914-2108)] and adolescent girls [1413 injuries per 100 000 population years (95% CI 1333-1498)]. For female adolescents and adults, knee joint/ligament injury was the outstanding injury type (20% in ages 13-17 years and 34% in ages 18-29 years). For children aged 7-12 years, more than half of the treated injuries involved the upper extremity; fractures constituted about one-third of these injuries. Conclusions: One of every 200 residents aged 0-59 years in typical Swedish counties each year sustained a traumatic football injury that required treatment in emergency healthcare. Further research on community-level patterns of overuse syndromes sustained by participation in football play is warranted.

Psychometric Properties of a New Instrument for Assessing Irrational Thoughts in Burn Victims (Scale of Irrational Thoughts After Burn Injuries).

The objective of this study was to develop and evaluate a scale for assessing irrational thoughts among burned patients. The present study was mixed (qualitative-methodologic) which was performed in several stages such as investigating similar or related scales, interviewing with patients and psychologists. Content validity was calculated by modified KAPPA basis on relevance and clarity. The reliability of the scale was measured using internal consistency and the test-retest method. To determine the construct validity, exploratory factor analysis approach using maximum likelihood extraction with varimax rotation was conducted. A total of 329 burned patients were recruited from Tehran, Tabriz, and Kermanshah provinces of Iran. Modified kappa scores were 0.80 and 0.91 for relevance and clarity of the items included in scale. The Cronbach alpha for overall scale, subscale 1, and subscale 2 were 0.89, 0.88, and 0.8, respectively. Test-retest reliability was also acceptable (intraclass correlation coefficient = 0.80). The best solution from the maximum likelihood analysis of the 39 items of the scale revealed two factors corresponding to the two subscales with 14 items that subscale 1 (self-acceptance) consisted of 10 statements accounting for 60% of the variance (eigenvalue = 5.04) and subscale 2 (distastefulness and pity) consisted of four statements accounting for 40% of the variance (eigenvalue = 1.53). The scale reflects acceptable levels of validity and reliability in assessing the irrational thoughts among Iranian patients. Moreover, the testing populations of both patients with burned faces and patients with other burned body parts indicates that the scale may also be applicable for patients' burn disfigurements on any part of their bodies.

Deep targeted sequencing in pediatric acute lymphoblastic leukemia unveils distinct mutational patterns between genetic subtypes and novel relapse-associated genes.

To characterize the mutational patterns of acute lymphoblastic leukemia (ALL) we performed deep next generation sequencing of 872 cancer genes in 172 diagnostic and 24 relapse samples from 172 pediatric ALL patients. We found an overall greater mutational burden and more driver mutations in T-cell ALL (T-ALL) patients compared to B-cell precursor ALL (BCP-ALL) patients. In addition, the majority of the mutations in T-ALL had occurred in the original leukemic clone, while most of the mutations in BCP-ALL were subclonal. BCP-ALL patients carrying any of the recurrent translocations ETV6-RUNX1, BCR-ABL or TCF3-PBX1 harbored few mutations in driver genes compared to other BCP-ALL patients. Specifically in BCP-ALL, we identified ATRX as a novel putative driver gene and uncovered an association between somatic mutations in the Notch signaling pathway at ALL diagnosis and increased risk of relapse. Furthermore, we identified EP300, ARID1A and SH2B3 as relapse-associated genes. The genes highlighted in our study were frequently involved in epigenetic regulation, associated with germline susceptibility to ALL, and present in minor subclones at diagnosis that became dominant at relapse. We observed a high degree of clonal heterogeneity and evolution between diagnosis and relapse in both BCP-ALL and T-ALL, which could have implications for the treatment efficiency.

The genetic basis for ecological adaptation of the Atlantic herring revealed by genome sequencing.

Ecological adaptation is of major relevance to speciation and sustainable population management, but the underlying genetic factors are typically hard to study in natural populations due to genetic differentiation caused by natural selection being confounded with genetic drift in subdivided populations. Here, we use whole genome population sequencing of Atlantic and Baltic herring to reveal the underlying genetic architecture at an unprecedented detailed resolution for both adaptation to a new niche environment and timing of reproduction. We identify almost 500 independent loci associated with a recent niche expansion from marine (Atlantic Ocean) to brackish waters (Baltic Sea), and more than 100 independent loci showing genetic differentiation between spring- and autumn-spawning populations irrespective of geographic origin. Our results show that both coding and non-coding changes contribute to adaptation. Haplotype blocks, often spanning multiple genes and maintained by selection, are associated with genetic differentiation.

The mutational landscape in pediatric acute lymphoblastic leukemia deciphered by whole genome sequencing.

Genomic characterization of pediatric acute lymphoblastic leukemia (ALL) has identified distinct patterns of genes and pathways altered in patients with well-defined genetic aberrations. To extend the spectrum of known somatic variants in ALL, we performed whole genome and transcriptome sequencing of three B-cell precursor patients, of which one carried the t(12;21)ETV6-RUNX1 translocation and two lacked a known primary genetic aberration, and one T-ALL patient. We found that each patient had a unique genome, with a combination of well-known and previously undetected genomic aberrations. By targeted sequencing in 168 patients, we identified KMT2D and KIF1B as novel putative driver genes. We also identified a putative regulatory non-coding variant that coincided with overexpression of the growth factor MDK. Our results contribute to an increased understanding of the biological mechanisms that lead to ALL and suggest that regulatory variants may be more important for cancer development than recognized to date. The heterogeneity of the genetic aberrations in ALL renders whole genome sequencing particularly well suited for analysis of somatic variants in both research and diagnostic applications.

A comparison of unintentional injury patterns occurring in two Swedish communities in 1978 and in 2008.

Surveillance and analyses of unintentional injuries can be used to help prioritise community prevention efforts. This study describes changes in local patterns for unintentional injuries resulting in deaths, hospitalisations, and outpatient visits to health care clinics and emergency rooms, comparing information from two different study periods, 1978 and 2008, in the Swedish communities of Falköping and Lidköping. Injury cases were analysed, and confidence intervals were derived. The study results show that while most injuries decreased comparing the first study period to the second, these changes were only significant in terms of decreases in outpatient care. This study points to the importance of more systematic collection data of injury events treated at the outpatient level, particularly for communities where there are relatively low numbers of injury-related deaths and hospitalisations.

Identification of candidate risk gene variations by whole-genome sequence analysis of four rat strains commonly used in inflammation research.

BACKGROUND: The DA rat strain is particularly susceptible to the induction of a number of chronic inflammatory diseases, such as models for rheumatoid arthritis and multiple sclerosis. Here we sequenced the genomes of two DA sub-strains and two disease resistant strains, E3 and PVG, previously used together with DA strains in genetically segregating crosses. RESULTS: The data uncovers genomic variations, such as single nucleotide variations (SNVs) and copy number variations that underlie phenotypic differences between the strains. Comparisons of regional differences between the two DA sub-strains identified 8 genomic regions that discriminate between the strains that together cover 38 Mbp and harbor 302 genes. We analyzed 10 fine-mapped quantitative trait loci and our data implicate strong candidates for genetic variations that mediate their effects. For example we could identify a single SNV candidate in a regulatory region of the gene Il21r, which has been associated to differential expression in both rats and human MS patients. In the APLEC complex we identified two SNVs in a highly conserved region, which could affect the regulation of all APLEC encoded genes and explain the polygenic differential expression seen in the complex. Furthermore, the non-synonymous SNV modifying aa153 of the Ncf1 protein was confirmed as the sole causative factor. CONCLUSION: This complete map of genetic differences between the most commonly used rat strains in inflammation research constitutes an important reference in understanding how genetic variations contribute to the traits of importance for inflammatory diseases.

Natural polymorphisms in Tap2 influence negative selection and CD4∶CD8 lineage commitment in the rat.

Genetic variation in the major histocompatibility complex (MHC) affects CD4∶CD8 lineage commitment and MHC expression. However, the contribution of specific genes in this gene-dense region has not yet been resolved. Nor has it been established whether the same genes regulate MHC expression and T cell selection. Here, we assessed the impact of natural genetic variation on MHC expression and CD4∶CD8 lineage commitment using two genetic models in the rat. First, we mapped Quantitative Trait Loci (QTLs) associated with variation in MHC class I and II protein expression and the CD4∶CD8 T cell ratio in outbred Heterogeneous Stock rats. We identified 10 QTLs across the genome and found that QTLs for the individual traits colocalized within a region spanning the MHC. To identify the genes underlying these overlapping QTLs, we generated a large panel of MHC-recombinant congenic strains, and refined the QTLs to two adjacent intervals of ∼0.25 Mb in the MHC-I and II regions, respectively. An interaction between these intervals affected MHC class I expression as well as negative selection and lineage commitment of CD8 single-positive (SP) thymocytes. We mapped this effect to the transporter associated with antigen processing 2 (Tap2) in the MHC-II region and the classical MHC class I gene(s) (RT1-A) in the MHC-I region. This interaction was revealed by a recombination between RT1-A and Tap2, which occurred in 0.2% of the rats. Variants of Tap2 have previously been shown to influence the antigenicity of MHC class I molecules by altering the MHC class I ligandome. Our results show that a restricted peptide repertoire on MHC class I molecules leads to reduced negative selection of CD8SP cells. To our knowledge, this is the first study showing how a recombination between natural alleles of genes in the MHC influences lineage commitment of T cells.

Epitope-specific antibody response is controlled by immunoglobulin V(H) polymorphisms.

Autoantibody formation is essential for the development of certain autoimmune diseases like rheumatoid arthritis (RA). Anti-type II collagen (CII) antibodies are found in RA patients; they interact with cartilage in vivo and are often highly pathogenic in the mouse. Autoreactivity to CII is directed to multiple epitopes and conserved between mice and humans. We have previously mapped the antibody response to CII in a heterogeneous stock cohort of mice, with a strong association with the IgH locus. We positioned the genetic polymorphisms and determined the structural requirements controlling antibody recognition of one of the major CII epitopes. Polymorphisms at positions S31R and W33T of the associated variable heavy chain (VH) allele were identified and confirmed by gene sequencing. The Fab fragment binding the J1 epitope was crystallized, and site-directed mutagenesis confirmed the importance of those two variants for antigen recognition. Back mutation to germline sequence provided evidence for a preexisting recognition of the J1 epitope. These data demonstrate a genetic association of epitope-specific antibody responses with specific VH alleles, and it highlights the importance of germline-encoded antibodies in the pathogenesis of antibody-mediated autoimmune diseases.

Protein expansion is primarily due to indels in intrinsically disordered regions.

Proteins evolve not only through point mutations but also by insertion and deletion events, which affect the length of the protein. It is well known that such indel events most frequently occur in surface-exposed loops. However, detailed analysis of indel events in distantly related and fast-evolving proteins is hampered by the difficulty involved in correctly aligning such sequences. Here, we circumvent this problem by first only analyzing homologous proteins based on length variation rather than pairwise alignments. Using this approach, we find a surprisingly strong relationship between difference in length and difference in the number of intrinsically disordered residues, where up to three quarters of the length variation can be explained by changes in the number of intrinsically disordered residues. Further, we find that disorder is common in both insertions and deletions. A more detailed analysis reveals that indel events do not induce disorder but rather that already disordered regions accrue indels, suggesting that there is a lowered selective pressure for indels to occur within intrinsically disordered regions.

Case analyses of all children's drowning deaths occurring in Sweden 1998-2007.

AIMS: The goal of this research project was to explore circumstances surrounding each drowning death occurring to children and adolescents ages 0-17 in Sweden during the years 1998-2007. METHODS: Records from the National Board of Forensic Medicine (NBFM) and other sources were analysed. We collected information on children's personal characteristics (sex, age, ethnic background, weight, height, physical condition, and pre-existing health conditions) and the circumstances of deaths (time and place of occurrence, type of drowning, resuscitation efforts and medical care given, for example). We also collected information on prevention factors: the physical environment, adult supervision, whether or not the child could swim, and if the child was using a personal flotation device at the time of death. RESULTS: Our analysis showed that 109 children had drowned in Sweden during the study period - of this group, 96 had died from unintentional causes. Children from immigrant backgrounds, particularly with families coming from the Middle East and Iran, were inordinately represented in the group of victims who had died from unintentional drowning deaths. Other risk factors included: coming from a single parent-headed family, alcohol use by older victims and a lack of ability to swim. CONCLUSIONS: Prevention efforts to prevent drowning in the future should focus on preventing alcohol use by young bathers; better fencing around swimming sites; improved coverage of swimming lessons to all children in Sweden, especially children from immigrant families; more education on drowning risks for single parents; and better awareness by adults on the need for constant supervision of children and adolescents in and near water.