Assessment of Seasonality and Extremely Preterm Birth in Denmark

IMPORTANCE

Preterm birth, particularly extremely preterm birth, has been associated with substantial morbidity and mortality. Research during SARS-CoV-2-related lockdowns revealed reductions in the more severe subtypes of preterm birth in some countries, suggesting the presence of preventable risk factors, such as infectious diseases or social behavior. Seasonality may provide a similar means of assessing natural changes in the daily life of pregnant individuals that were similar to those experienced during the COVID-19 lockdown period.

OBJECTIVE

To evaluate the association between seasonality and extremely preterm birth.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide cohort study included 1 136 143 pregnancies in Denmark with onset between January 1, 1997, and December 31, 2016, in which the fetuses survived 21 completed weeks of gestation. Pregnancies were followed up until preterm birth, fetal death, or 37 completed weeks of gestation. Data were analyzed from September 2020 to September 2021.

EXPOSURES

Season during gestation (primary exposure) and season of pregnancy onset.

MAIN OUTCOMES AND MEASURES

The main outcome of extremely preterm birth was defined as a live birth occurring between 22 weeks, 0 days' gestation and 27 weeks, 6 days' gestation. Cox regression analyses were used to estimate hazard ratios (HRs) for season during gestation and season of pregnancy onset, with adjustment for socioeconomic and demographic factors.

RESULTS

Among 662 338 pregnant individuals, the median age at pregnancy onset was 30.0 years (IQR, 6.0 years). Of 1 136 143 pregnancies, 2009 extremely preterm births (cumulative incidence, 0.18%) were identified during follow-up. Season during gestation was associated with extremely preterm birth, with cumulative incidences of 0.17% (95% CI, 0.16%-0.19%) in spring, 0.18% (95% CI, 0.17%-0.20%) in summer, 0.20% (95% CI, 0.18%-0.21%) in autumn, and 0.16% (95% CI, 0.14%-0.17%) in winter. Compared with winter, the adjusted HRs (AHRs) for the risk of extremely preterm birth were 1.11 (95% CI, 0.97-1.26) for spring, 1.15 (95% CI, 1.02-1.31) for summer, and 1.25 (95% CI, 1.10-1.42) for autumn. The number of extremely preterm births associated with the increased risk in the spring, summer, and autumn was 56.1 (95% CI, 18.2-99.7), representing 2.8% (95% CI, 0.9%-5.0%) of all extremely preterm births in the study. Season of pregnancy onset was not associated with the risk of extremely preterm birth in spring (AHR, 0.98; 95% CI, 0.95-1.01) or summer (AHR, 1.00; 95% CI, 0.96-1.03) compared with winter, but a slight increase in risk was observed in autumn (AHR, 1.05; 95% CI, 1.02-1.09) compared with winter.

CONCLUSIONS AND RELEVANCE

In this large, national cohort study, seasonality was associated with 2.8% of all extremely preterm births. Season during gestation was associated with the rate of extremely preterm birth, suggesting the presence of potential risk factors associated with season that may be preventable. Further research to identify risk factors for extremely preterm birth associated with seasonality is warranted.

Genome-wide association study identifies locus at chromosome 2q32.1 associated with syncope and collapse

Aims

Syncope is a common condition associated with frequent hospitalization or visits to the emergency department. Family aggregation and twin studies have shown that syncope has a heritable component. We investigated whether common genetic variants predispose to syncope and collapse.

Methods and results

We used genome-wide association data on syncope on 408 961 individuals with European ancestry from the UK Biobank study. In a replication study, we used the Integrative Psychiatric Research Consortium (iPSYCH) cohort (n = 86 189), to investigate the risk of incident syncope stratified by genotype carrier status. We report on a genome-wide significant locus located on chromosome 2q32.1 [odds ratio = 1.13, 95% confidence interval (CI) 1.10–1.17, P = 5.8 × 10⁻¹⁵], with lead single nucleotide polymorphism rs12465214 in proximity to the gene zinc finger protein 804a (ZNF804A). This association was also shown in the iPSYCH cohort, where homozygous carriers of the C allele conferred an increased hazard ratio (1.30, 95% CI 1.15–1.46, P = 1.68 × 10⁻⁵) of incident syncope. Quantitative polymerase chain reaction analysis showed ZNF804A to be expressed most abundantly in brain tissue.

Conclusion

We identified a genome-wide significant locus (rs12465214) associated with syncope and collapse. The association was replicated in an independent cohort. This is the first genome-wide association study to associate a locus with syncope and collapse.

4259Discovery of the first genome-wide significant risk loci for syncope and collapse

Background

Syncope is a common condition in the general population causing frequent hospitalisation and visits to the emergency department. Family aggregation and twin studies have previously indicated that syncope and collapse has a heritable component.

Purpose

We investigated whether common genetic variants predispose to syncope and collapse.

Methods

We used genome-wide association data on syncope and collapse for 408,961 individuals with European ancestry from the UK Biobank study. In a replication study, the Integrative Psychiatric Research Consortium (iPSYCH) cohort (n=86,189) was used to investigate the risk of incident syncope stratified by genotype carrier status.

Results

We report on a genome-wide significant locus on chromosome 2q32.1 with the lead SNP rs12465214 (odds ratio [OR] = 1.13, 95% confidence interval [CI] = 1.10–1.17, P=5.8x10–15; Figure 1a). This association was replicated in the iPSYCH cohort, where homozygous carriers of the C allele conferred an increased hazard ratio (HR=1.30, CI: 1.15–1.46, P=1.68x10–5; Figure 1b). LD score regression demonstrated a significant genetic correlation (rg) with coronary artery disease (rg=0.41, P=6.99x10–15) and related phenotypes such as angina and hypertension (Figure 1c). Analyses of eQTL (P=4x10–8) and epigenetic chromatin states revealed that variation in this locus likely affects expression of the gene ZNF804A, which resides in its proximity (Figure 1d). A qPCR analysis showed that ZNF804A was mostly expressed in the brain. A lower level of ZNF804A expression was also detected in the cerebral arteries. ZNF804A was not expressed in heart tissue.

Figure 1

Conclusion

rs12465214 is associated with syncope and collapse. Variation in this locus likely modulates the expression of the nearby gene ZNF804A through eQTLs and chromatin interactions. ZNF804A is mainly expressed in the brain and cerebral arteries. However, the precise function of ZNF804A is unknown. Furthermore, syncope and collapse is a polygenetic trait and share a significant genetic overlap with coronary artery disease, angina and hypertension.

Acknowledgement/Funding

This work was supported by grants from The John and Birthe Meyer Foundation, The Research Foundation of the Heart Centre, Rigshospitalet, The Research

Cytochrome P450 polymorphism and postoperative cognitive dysfunction

BACKGROUND

The etiology of postoperative cognitive dysfunction (POCD) remains unclear but toxicity of anesthetic drugs and their metabolites could be important. We aimed to assess the possible association between POCD after propofol anesthesia and various phenotypes owing to polymorphisms in cytochrome P450 encoding genes.

METHODS

We included patients who underwent non-cardiac surgery under total intravenous anesthesia with propofol. POCD was identified using a neuropsychological test-battery administered preoperatively, one week, and three months after surgery. Genotyping of CYP2C19*2, *3, CYP2D6*3, *4, *5 and *6 was performed using pyrosequencing, and patients were characterized according to their phenotype as ultra, extensive, intermediate, or poor metabolizers.

RESULTS

In total, 337 patients with a median age of 67 years were included. 30 (9.4%) out of the 319 patients who underwent neuropsychological testing at one week had POCD, and 24 out of 307 (7.8%) had POCD at three months. None of the examined CYP2C19, 2D6 alleles, or various phenotypes were significantly associated with POCD.

CONCLUSION

Polymorphisms in CYP2C19, or 2D6 genes do not seem to be related to the occurrence of cognitive dysfunction after non-cardiac surgery in patients anesthetised with propofol.

Mutations in sodium channel β-subunit SCN3B are associated with early-onset lone atrial fibrillation

AIMS

Atrial fibrillation (AF) is the most frequent arrhythmia. Screening of SCN5A-the gene encoding the α-subunit of the cardiac sodium channel-has indicated that disturbances of the sodium current may play a central role in the mechanism of lone AF. We tested the hypothesis that lone AF in young patients is associated with genetic mutations in SCN3B and SCN4B, the genes encoding the two β-subunits of the cardiac sodium channel.

METHODS AND RESULTS

In 192 unrelated lone AF patients, the entire coding sequence and splice junctions of SCN3B and SCN4B were bidirectionally sequenced. Three non-synonymous mutations were found in SCN3B (R6K, L10P, and M161T). Two mutations were novel (R6K and M161T). None of the mutations were present in the control group (n = 432 alleles), nor have any been previously reported in conjunction with AF. All SCN3B mutations affected residues that are evolutionarily conserved across species. Electrophysiological studies on the SCN3B mutation were carried out and all three SCN3B mutations caused a functionally reduced sodium channel current. One synonymous variant was found in SCN4B.

CONCLUSION

In 192 young lone AF patients, we found three patients with suspected disease-causing non-synonymous mutations in SCN3B, indicating that mutations in this gene contribute to the mechanism of lone AF. The three mutations in SCN3B were investigated electrophysiologically and all led to loss of function in the sodium current, supporting the hypothesis that decreased sodium current enhances AF susceptibility.

Hereditary hemochromatosis (HFE) genotypes in heart failure: relation to etiology and prognosis

Background

It is believed that hereditary hemochromatosis (HH) might play a role in cardiac disease (heart failure (HF) and ischemia). Mutations within several genes are HH-associated, the most common being the HFE gene. In a large cohort of HF patients, we sought to determine the etiological role and the prognostic significance of HFE genotypes.

Methods

We studied 667 HF patients (72.7% men) with depressed systolic function, enrolled in a multicentre trial with a follow-up period of up to 5 years. All were genotyped for the known HFE variants C282Y, H63D and S65C.

Results

The genotype and allele frequencies in the HF group were similar to the frequencies determined in the general Danish population. In multivariable analysis mortality was not predicted by C282Y-carrier status (HR 1.2, 95% CI: 0.8-1.7); H63D-carrier status (HR 1.0, 95% CI: 0.7-1.3); nor S65C-carrier status (HR 1.2, 95% CI: 0.7-2.0). We identified 27 (4.1%) homozygous or compound heterozygous carriers of HFE variants. None of these carriers had a clinical presentation suggesting hemochromatosis, but hemoglobin and ferritin levels were higher than in the rest of the cohort. Furthermore, a trend towards reduced mortality was seen in this group in univariate analyses (HR 0.4, 95% CI: 0.2-0.9, p = 0.03), but not in multivariate (HR 0.5, 95% CI: 0.2-1.2).

Conclusion

HFE genotypes do not seem to be a significant contributor to the etiology of heart failure in Denmark. HFE variants do not affect mortality in HF.

Diagnostic yield, interpretation, and clinical utility of mutation screening of sarcomere encoding genes in Danish hypertrophic cardiomyopathy patients and relatives

The American Heart Association (AHA) recommends family screening for hypertrophic cardiomyopathy (HCM). We assessed the outcome of family screening combining clinical evaluation and screening for sarcomere gene mutations in a cohort of 90 Danish HCM patients and their close relatives, in all 451 persons. Index patients were screened for mutations in all coding regions of 10 sarcomere genes (MYH7, MYL3, MYBPC3, TNNI3, TNNT2, TPM1, ACTC, CSRP3, TCAP, and TNNC1) and five exons of TTN. Relatives were screened for presence of minor or major diagnostic criteria for HCM and tracking of DNA variants was performed. In total, 297 adult relatives (>18 years) (51.2%) fulfilled one or more criteria for HCM. A total of 38 HCM-causing mutations were detected in 32 index patients. Six patients carried two disease-associated mutations. Twenty-two mutations have only been identified in the present cohort. The genetic diagnostic yield was almost twice as high in familial HCM (53%) vs. HCM of sporadic or unclear inheritance (19%). The yield was highest in families with an additional history of HCM-related clinical events. In relatives, 29.9% of mutation carriers did not fulfil any clinical diagnostic criterion, and in 37.5% of relatives without a mutation, one or more criteria was fulfilled. A total of 60% of family members had no mutation and could be reassured and further follow-up ceased. Genetic diagnosis may be established in approximately 40% of families with the highest yield in familial HCM with clinical events. Mutation-screening was superior to clinical investigation in identification of individuals not at increased risk, where follow-up is redundant, but should be offered in all families with relatives at risk for developing HCM.

Neural control of heart rate is an arrhythmia risk modifier in long QT syndrome

OBJECTIVES

The purpose of this study was to test the hypothesis that differences in autonomic responses might modify clinical severity in long QT syndrome type 1 (LQT1) patients, those with KCNQ1 mutations and reduced I(Ks), in whom the main arrhythmia trigger is sympathetic activation.

BACKGROUND

Some long QT syndrome (LQTS) patients experience life-threatening cardiac arrhythmias, whereas others remain asymptomatic throughout life. This clinical heterogeneity is currently unexplained.

METHODS

In a South African LQT1 founder population segregating KCNQ1-A341V, we correlated major cardiac events to resting heart rate (HR) and to baroreflex sensitivity (BRS) on and off beta-adrenergic blockers (BB).

RESULTS

In 56 mutation carriers (MCs), mean HR was lower among asymptomatic patients (p < 0.05). Among MCs with a QT interval corrected for heart rate <or=500 ms, those in the lower HR tertile were less likely to have suffered prior cardiac events (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.04 to 0.79, p < 0.02). The BRS was lower among asymptomatic than symptomatic MCs (11.8 +/- 3.5 ms/mm Hg vs. 20.1 +/- 10.9 ms/mm Hg, p < 0.05). A BRS in the lower tertile was associated with a lower probability of being symptomatic (OR 0.13, 95% CI 0.02 to 0.96, p < 0.05). A similar trend was observed during BB. The MCs in the lower tertile for both HR and BRS were less frequently symptomatic than MCs with different patterns (20% vs. 76%, p < 0.05). Subjects with either ADRA2C-Del322-325 or homozygous for ADRB1-R389, 2 polymorphisms predicting enhanced adrenergic response, were more likely to have BRS values above the upper tertile (45% vs. 8%, p < 0.05).

CONCLUSIONS

Lower resting HR and "relatively low" BRS are protective factors in KCNQ1-A341V carriers. A plausible underlying mechanism is that blunted autonomic responses prevent rapid HR changes, arrhythmogenic when I(Ks) is reduced. These findings help understanding phenotypic heterogeneity in LQTS and identify a physiological risk modifier, which is probably genetically determined.

High-efficiency multiplex capillary electrophoresis single strand conformation polymorphism (multi-CE-SSCP) mutation screening of SCN5A: a rapid genetic approach to cardiac arrhythmia

Mutations in the SCN5A gene coding for the alpha-subunit of the cardiac Na(+) ion channel cause long QT syndrome, Brugada syndrome, idiopathic ventricular fibrillation, sick sinus node syndrome, progressive conduction disease, dilated cardiomyopathy and atrial standstill. These diseases exhibit variable expressivity, and identification of gene carriers is clinically important, particularly in sudden infant and adult death syndromes. The SCN5A gene comprises 28 exons distributed over 100 kbp of genomic sequence at chromosome 3p21. Disease-causing mutations are private and scattered over the DNA sequence, making it difficult to screen for specific mutations. We developed a multiplex capillary-electrophoresis single-strand conformation polymorphism (Multi-CE-SSCP) mutation screening protocol on the ABI 3100 platform and applied it to 10 previously slab-gel SSCP identified mutations and SNPs and used it to identify one novel deletion. The method is highly efficient, with a turnover of 23 patients per 24 h and a false positive rate of 0.5% of the analyzed amplicons. Each variant has a particular elution pattern, and all 20 carriers of the H558R polymorphism out of 57 persons were correctly identified. We suggest that the method could become part of routine work-up of patients with suspicious syncope and of members of families with sudden unexplained death.

Phenotypic Variability and Unusual Clinical Severity of Congenital Long-QT Syndrome in a Founder Population

Background— In the congenital long-QT syndrome (LQTS), there can be a marked phenotypic heterogeneity. Founder effects, by which many individuals share a mutation identical by descent, represent a powerful tool to further understand the underlying mechanisms and to predict the natural history of mutation-associated effects. We are investigating one such founder effect, originating in South Africa in approximately ad 1700 and segregating the same KCNQ1 mutation (A341V).

Methods and Results— The study population involved 320 subjects, 166 mutation carriers (MCs) and 154 noncarriers. When not taking β-blocker therapy, MCs had a wide range of QTc values (406 to 676 ms), and 12% of individuals had a normal QTc (≤440 ms). A QTc >500 ms was associated with increased risk for cardiac events (OR=4.22; 95% CI, 1.12 to 15.80; P =0.033). We also found that MCs with a heart rate <73 bpm were at significantly lower risk (OR=0.23; 95% CI, 0.06 to 0.86; P =0.035). This study also unexpectedly determined that KCNQ1-A341V is associated with greater risk than that reported for large databases of LQT1 patients: A341V MCs are more symptomatic by age 40 years (79% versus 30%) and become symptomatic earlier (7±4 versus 13±9 years, both P <0.001). Accordingly, functional studies of KCNQ1-A341V in CHO cells stably expressing IK s were conducted and identified a dominant negative effect of the mutation on wild-type channels.

Conclusions— KCNQ1-A341V is a mutation associated with an unusually severe phenotype, most likely caused by the dominant negative effect of the mutation. The availability of an extended kindred with a common mutation allowed us to identify heart rate, an autonomic marker, as a novel risk factor.

Automated quality assurance and patient dosimetry in diagnostic radiology

It has been generally considered that improved methods of quality assurance would reduce the population dose from diagnostic radiology. This paper describes the development of a computerized method of automatically monitoring tube and generator parameters to perform on-line quality assurance, whilst undertaking various patient dosimetry measurements and calculations for each exposure. The method involves interfacing a microcomputer to a microprocessor controlled X-ray generator. Details of the various interfacing methods and modifications to the X-ray unit are given. The instrument enables quality assurance to be performed for every exposure by comparing tube and generator parameters against nominal settings. The software automatically warns the operator of any deviations from accepted limiting values. When a patient is examined, details of the examination and projection are entered into a database. The exposure area product and field size are monitored for each exposure. This data, together with information on tube potential and examination/projection is used to deduce patient entrance skin dose and energy imparted. Doses to individual organs are estimated using normalized organ dose data and a knowledge of tube potential and field size.

An instrument for monitoring the force applied by breast compression devices on mammography x-ray sets

Automatic breast compression devices are commonly fitted to mammographic x-ray sets. The force exerted by these compression devices should be limited and periodically checked. This article describes the design and construction of an instrument for the routine assessment of the force applied by breast compression devices on mammography x-ray sets. Results obtained on four different mammography x-ray units are presented. In addition, data on the effect of compression plate design on compression force is given for one unit. The instrument has proved to be a simple and quick method of monitoring the force applied by the compression plates on mammographic x-ray units.