Lisbeth Carstensen

Familial Aggregation of Lone Atrial Fibrillation in Young Persons

OBJECTIVES This study investigated whether an individuals risk of developing lone atrial fibrillation (AF) before age 60 years is associated with lone AF in relatives. BACKGROUND Genetic factors may play a role in the development of lone AF. METHODS Using Danish national registers, a cohort was established of ~4 million persons born between 1950 and 2008, and those with a family history of lone AF (AF without preceding cardiovascular/endocrine diagnoses) were identified. Individuals were followed up until the first diagnosis of lone AF. Poisson regression was used to estimate incidence rate ratios (IRRs). RESULTS In ~92 million person-years of follow-up, 9,507 persons were identified as having lone AF. The IRRs for lone AF given an affected first- or second-degree relative were 3.48 (95% confidence interval [CI]: 3.08 to 3.93) and 1.64 (95% CI: 1.04 to 2.59), respectively. IRRs were higher for men than for women but were not associated with the affected relatives sex. IRR for lone AF was 6.24 (95% CI: 2.59 to 15.0), given at least 2 first-degree relatives affected with lone AF. The IRR for lone AF in persons aged <40 years given a first-degree relative affected at age <40 years was 5.42 (95% CI: 3.80 to 7.72), and 8.53 (95% CI: 3.82 to 19.0) in persons age <30 years given a first-degree relative affected at age <30 years. CONCLUSIONS A family history of lone AF is associated with substantial risk of lone AF, with the strongest risks associated with young age at onset, multiple affected relatives, and in first-degree relatives. These results suggest routine evaluation of the families of at least certain types of patients with lone AF.

Genome-wide association analyses identify variants in developmental genes associated with hypospadias

Hypospadias is a common congenital condition in boys in which the urethra opens on the underside of the penis. We performed a genome-wide association study on 1,006 surgery-confirmed hypospadias cases and 5,486 controls from Denmark. After replication genotyping of an additional 1,972 cases and 1,812 controls from Denmark, the Netherlands and Sweden, 18 genomic regions showed independent association with P < 5 × 10−8. Together, these loci explain 9% of the liability to developing this condition. Several of the identified regions harbor genes with key roles in embryonic development (including HOXA4, IRX5, IRX6 and EYA1). Subsequent pathway analysis with GRAIL and DEPICT provided additional insight into possible genetic mechanisms causing hypospadias.

Common variants associated with general and MMR vaccine-related febrile seizures

Febrile seizures represent a serious adverse event following measles, mumps and rubella (MMR) vaccination. We conducted a series of genome-wide association scans comparing children with MMR-related febrile seizures, children with febrile seizures unrelated to vaccination and controls with no history of febrile seizures. Two loci were distinctly associated with MMR-related febrile seizures, harboring the interferon-stimulated gene IFI44L (rs273259: P = 5.9 × 10−12 versus controls, P = 1.2 × 10−9 versus MMR-unrelated febrile seizures) and the measles virus receptor CD46 (rs1318653: P = 9.6 × 10−11 versus controls, P = 1.6 × 10−9 versus MMR-unrelated febrile seizures). Furthermore, four loci were associated with febrile seizures in general, implicating the sodium channel genes SCN1A (rs6432860: P = 2.2 × 10−16) and SCN2A (rs3769955: P = 3.1 × 10−10), a TMEM16 family gene (ANO3; rs114444506: P = 3.7 × 10−20) and a region associated with magnesium levels (12q21.33; rs11105468: P = 3.4 × 10−11). Finally, we show the functional relevance of ANO3 (TMEM16C) with electrophysiological experiments in wild-type and knockout rats.

Family history of premature death and risk of early onset cardiovascular disease.

OBJECTIVES The purpose of this study was to examine the effect of a family history of premature death, cardiovascular death in particular, on the risk of early cardiovascular disease. BACKGROUND Studies suggest that fatal cardiovascular events and less severe cardiovascular diseases may co-occur in families. Consequently, a family history of premature death may indicate a familial cardiac frailty that predisposes to early cardiovascular disease. METHODS We ascertained family history of premature death (age <60 years) in all individuals born in Denmark from 1950 to 2008 and followed this cohort for early cardiovascular disease (age <50 years). Using Poisson regression, we estimated incidence rate ratios (IRRs) reflecting the effect of premature death in the family on early cardiovascular disease risk. RESULTS Among 3,985,301 persons followed up for 89,294,258 person-years, 129,825, 31,172, and 5,214 were diagnosed with any early cardiovascular disease, ischemic heart disease, and ventricular arrhythmia, respectively. IRRs for these conditions given a history of premature cardiovascular death in first-degree relatives were 1.72 (95% confidence interval [CI]: 1.68 to 1.77), 2.21 (95% CI: 2.11 to 2.31), and 1.94 (95% CI: 1.70 to 2.20), respectively. With ≥2 cardiovascular deaths in a family, corresponding IRRs were 3.30 (95% CI: 2.77 to 3.94), 5.00 (95% CI: 3.87 to 6.45), and 6.18 (95% CI: 3.32 to 11.50). The IRR for any early cardiovascular disease given a family history of premature noncardiovascular death was significantly lower, 1.12 (95% CI: 1.10 to 1.14) (p(cardiac vs. noncardiac) < 0.0001). CONCLUSIONS Family history of premature cardiovascular death was consistently and significantly associated with a risk of early cardiovascular disease, suggesting an inherited cardiac vulnerability. These results should be kept in mind when assessing cardiovascular disease risk in persons with a family history of premature cardiovascular death.

The effectiveness of BCG vaccination in preventing Mycobacterium tuberculosis infection and disease in Greenland

Background The BCG vaccines ability to prevent Mycobacterium tuberculosis infection (MTI) remains highly debated. In Greenland, BCG vaccination was introduced in 1955, but was temporarily discontinued (1991–1996) due to nationwide policy changes. The study aimed to use the transient stop in BCG vaccination to evaluate the effect of vaccination on MTI prevalence and TB incidence. Methods MTI study: A cross-sectional study (2012), comprising East Greenlanders born during 1982–2006, evaluated the effect of BCG vaccination on MTI prevalence; a positive interferon γ release assay defined an MTI case. Associations were estimated using logistic regression. TB study: a cohort study covering the same birth cohorts with follow-up until 2012 evaluated the vaccines effect on TB incidence. A personal identifier allowed for follow-up in the TB notification system. Associations were estimated using Cox regression. Results MTI study: Included 953 participants; 81% were BCG-vaccinated; 29% had MTI, 23% among vaccinated and 57% among non-vaccinated. BCG vaccination reduced the odds of MTI, OR 0.52 (95% CI 0.32 to 0.85), p=0.01. Vaccine effectiveness against MTI was 20%. TB study: Included 1697 participants followed for 21 148 person-years. 6% were notified with TB, 4% among vaccinated and 11% among non-vaccinated. BCG vaccination reduced the risk of TB, HR 0.50 (95% CI 0.26 to 0.95), p=0.03, yielding a vaccine effectiveness of 50%. Conclusions BCG vaccination was effective in reducing both MTI and TB disease among children and young adults in a TB high-endemic setting in Greenland.

Plasma lipids, genetic variants near APOA1, and the risk of infantile hypertrophic pyloric stenosis.

IMPORTANCE Infantile hypertrophic pyloric stenosis (IHPS) is a serious condition in which hypertrophy of the pyloric sphincter muscle layer leads to gastric outlet obstruction. Infantile hypertrophic pyloric stenosis shows strong familial aggregation and heritability, but knowledge about specific genetic risk variants is limited. OBJECTIVES To search the genome comprehensively for genetic associations with IHPS and validate findings in 3 independent sample sets. DESIGN, SETTING, AND PARTICIPANTS During stage 1, we used reference data from the 1000 Genomes Project for imputation into a genome-wide data set of 1001 Danish surgery-confirmed samples (cases diagnosed 1987-2008) and 2371 disease-free controls. In stage 2, the 5 most significantly associated loci were tested in independent case-control sample sets from Denmark (cases diagnosed 1983-2010), Sweden (cases diagnosed 1958-2011), and the United States (cases diagnosed 1998-2005), with a total of 1663 cases and 2315 controls. MAIN OUTCOMES AND MEASURES Association of genetic variation with the presence of infantile hypertrophic pyloric stenosis. RESULTS We found a new genome-wide significant locus for IHPS at chromosome 11q23.3. The single-nucleotide polymorphism (SNP) with the lowest P value at the locus, rs12721025 (odds ratio [OR], 1.59; 95% CI, 1.38-1.83; P = 1.9 × 10(-10)), is located 301 bases downstream of the apolipoprotein A-I (APOA1) gene and is correlated (r2 between 0.46 and 0.80) with SNPs previously found to be associated with levels of circulating cholesterol. For these SNPs, the cholesterol-lowering allele consistently was associated with increased risk of IHPS. CONCLUSIONS AND RELEVANCE This study identified a new genome-wide significant locus for IHPS. Characteristics of this locus suggest the possibility of an inverse relationship between levels of circulating cholesterol in neonates and IHPS risk, which warrants further investigation.

Epilepsy, anti-epileptic medication use and risk of cancer

Whether the powerful medications used to treat epilepsy increase the risk of cancer has been debated for decades, but until now no study could disentangle the contributions of anti‐epileptic medications and epilepsy itself to cancer risk. Using a cohort comprising all Danish residents ≥16 years old at some point during the period 1996–2010 (>56 million person‐years of follow‐up) and information from national health registers, we examined associations between anti‐epileptic medication use and cancer rates in persons with and without epilepsy, and between epilepsy and cancer rates in treated and untreated individuals. Associations were expressed as incidence rate ratios (IRRs) estimated using Poisson regression. Among persons without epilepsy, use of anti‐epileptic medication increased the rates of most cancers little or not at all, although we observed moderately increased rates of liver, mouth and throat, and respiratory tract cancers (IRRs 1.40–1.59). In contrast, we observed strong associations between epilepsy and the rates of central nervous system and mouth and throat cancers (IRRs 2.00–3.91), and a modest association between epilepsy and the rate of respiratory tract cancers (IRRs 1.30–1.35), independent of anti‐epileptic medication use. Our finding of only modest increases in cancer risk directly attributable to anti‐epileptic medication use suggests that these medications may not be as strongly carcinogenic as has been feared, and that it is not primarily anti‐epileptic medications that are responsible for the increased cancer risk among epileptics but another aspect of epilepsy diagnosis or treatment or an etiologic factor common to the two conditions.

Risk of Cardiomyopathy in Younger Persons With a Family History of Death from Cardiomyopathy A Nationwide Family Study in a Cohort of 3.9 Million Persons

Background— Recommendations for presymptomatic screening of relatives of cardiomyopathy patients are based on findings from tertiary centers. Cardiomyopathy inheritance patterns are fairly well understood, but how cardiomyopathy in younger persons (<50 years) aggregates in families at the population level is unclear. In a nationwide cohort, we examined the risk of cardiomyopathy by family history of premature death (<60 years) from cardiomyopathy. Methods and Results— By linking Danish national register data, we constructed a cohort of 3.9 million persons born from 1950 to 2008. We ascertained family history of premature (<60 years) death from cardiomyopathy or other conditions, and cohort members were followed from 1977 to 2008 for cardiomyopathy diagnosed at <50 years. We identified 3890 cardiomyopathies in 89 million person-years of follow-up. Using Poisson regression, we estimated incidence rate ratios for cardiomyopathy by family history of premature death. Premature cardiomyopathy deaths in first- and second-degree relatives were associated with 29- and 6-fold increases in the rate of cardiomyopathy, respectively. If the first-degree relative died aged <35 years, the rate of cardiomyopathy increased 100-fold; given ≥2 premature deaths in first-degree relatives, the rate increased more than 400-fold. In contrast, a family history of premature death from other cardiac or noncardiac conditions increased the rate of cardiomyopathy 3-fold at most. Conclusions— A family history of premature cardiomyopathy death was associated with an increase in risk of cardiomyopathy ranging from 6- to 400-fold, depending on age, kinship, gender and number of affected family members. Our general population-based results support recommendations for presymptomatic screening of relatives of cardiomyopathy patients.

Genome-wide association study of Hirschsprung disease detects a novel low-frequency variant at the RET locus

Hirschsprung disease (HSCR) is a congenital disorder with a population incidence of ~1/5000 live births, defined by an absence of enteric ganglia along variable lengths of the colon. HSCR genome-wide association studies (GWAS) have found common associated variants at RET, SEMA3, and NRG1, but they still fail to explain all of its heritability. To enhance gene discovery, we performed a GWAS of 170 cases identified from the Danish nationwide pathology registry with 4717 controls, based on 6.2 million variants imputed from the haplotype reference consortium panel. We found a novel low-frequency variant (rs144432435), which, when conditioning on the lead RET single-nucleotide polymorphism (SNP), was of genome-wide significance in the discovery analysis. This conditional association signal was replicated in a Swedish HSCR cohort with discovery plus replication meta-analysis conditional odds ratio of 6.6 (P = 7.7 × 10−10; 322 cases and 4893 controls). The conditional signal was, however, not replicated in two HSCR cohorts from USA and Finland, leading to the hypothesis that rs144432435 tags a rare haplotype present in Denmark and Sweden. Using the genome-wide complex trait analysis method, we estimated the SNP heritability of HSCR to be 88%, close to estimates based on classical family studies. Moreover, by using Lasso (least absolute shrinkage and selection operator) regression we were able to construct a genetic HSCR predictor with a area under the receiver operator characteristics curve of 76% in an independent validation set. In conclusion, we combined the largest collection of sporadic Hirschsprung cases to date (586 cases) to further elucidate HSCR’s genetic architecture.

Author's response: BCG and infection with Mycobacterium tuberculosis

Thanks to Turner et al for commenting on our article. Turner et al challenge our finding that the Bacillus Calmette-Guerin vaccine (BCG) can prevent Mycobacterium tuberculosis infection (MTI), and propose an alternative explanation: that the absence of a positive interferon gamma release assay (IGRA) could be due to antigenic sin and does not necessarily demonstrate absence of infection. A positive IGRA is the best available surrogate for MTI, but we are fully aware of its limitations. With the IGRA test, MTI is defined by a T-cell-induced interferon gamma response to M tuberculosis antigens …