Sleep bruxism: The past, the present, and the future-evolution of a concept

BACKGROUND

The concept of sleep bruxism (SB) has evolved exponentially over the past several decades. Many theories and hypotheses have been proposed as to the definition, pathophysiology, and management of SB, from the early 1960s through the present. The role of peripheral factors, such as dental occlusion, in the pathogenesis of SB has been discarded.

TYPES OF STUDIES REVIEWED

The authors searched several electronic databases (ie, PubMed, Google Scholar, Web of Science, Embase, and Ovid MEDLINE) for studies on bruxism. The search was conducted from January 1961 through May 2023 and yielded 4,612 articles, of which 312 were selected for comprehensive review after eliminating duplicates and nonfocused articles.

RESULTS

There has been an evident progressive shift from the role of peripheral factors, such as dental occlusion, to more central factors, such as the involvement of a central pattern generator as well as the autonomic nervous system, in the genesis of bruxing movements. There is continued robust interest in the dental community to elucidate the contributing factors involved in SB.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The neurophysiology of SB appears to be leaning more toward central rather than peripheral factors. There is increasing evidence of the role of the autonomic nervous system, genetics, and comorbidities in the genesis of SB. The scientific literature seems to refute the role of dental occlusion in the causation of bruxing movements. As per the literature, there has been a paradigm shift in the definition and genesis of SB and its possible dental implications and management, which also highlights the need for succinct scientific studies in this regard.

Needlestick injuries in dentistry: Time to revisit

BACKGROUND

Blood-borne pathogens (BBPs) are infectious microorganisms that are found in human blood and can cause diseases in humans. Health care workers such as physicians, surgeons, nurses, dentists, dental students, dental assistants, laboratory technicians, personnel handling infectious waste, and other health care employees are at increased risk of exposure to these pathogens. Percutaneous injuries from needles or other sharp objects are the major sources of BBPs in the workplace. Needlestick injuries (NSIs) have the most potential to transmit and have the easiest mode of transmission of BBPs.

TYPES OF STUDIES REVIEWED

The authors searched electronic databases (PubMed, Web of Science, Google Scholar, Scopus, Embase, MEDLINE-Ovid) for studies and articles focused on the various aspects of NSIs, their possible causes, prevention, and management protocols.

RESULTS

There is a lack of literature on the global prevalence of NSIs among dental practitioners and underreporting of NSIs by clinicians. The authors also found that dental students and inexperienced practitioners were the most vulnerable. They found apparent inconsistencies in guidelines and recommendations from various regulatory and statutory agencies in charge of limiting and managing NSIs.

CONCLUSION

The most significant occupational risks for health care workers globally are NSIs. Dentists are recognized as one of the high-risk groups for exposure to NSIs. Although the reporting rate was noticeably low, the frequency of NSIs among dental students was alarmingly high.

PRACTICAL IMPLICATIONS

Appropriate and succinct training of dental health care workers is crucial for prevention and management of NSIs. It is recommended that dentists familiarize themselves with recommendations from such agencies and organizations as the Center for Disease Control and Prevention, Occupational Safety and Health Administration, and American Dental Association.

Richer than Gold: the fungal biodiversity of Reserva Los Cedros, a threatened Andean cloud forest

BACKGROUND

Globally, many undescribed fungal taxa reside in the hyperdiverse, yet undersampled, tropics. These species are under increasing threat from habitat destruction by expanding extractive industry, in addition to global climate change and other threats. Reserva Los Cedros is a primary cloud forest reserve of ~ 5256 ha, and is among the last unlogged watersheds on the western slope of the Ecuadorian Andes. No major fungal survey has been done there, presenting an opportunity to document fungi in primary forest in an underrepresented habitat and location. Above-ground surveys from 2008 to 2019 resulted in 1760 vouchered collections, cataloged and deposited at QCNE in Ecuador, mostly Agaricales sensu lato and Xylariales. We document diversity using a combination of ITS barcode sequencing and digital photography, and share the information via public repositories (GenBank & iNaturalist).

RESULTS

Preliminary identifications indicate the presence of at least 727 unique fungal species within the Reserve, representing 4 phyla, 17 classes, 40 orders, 101 families, and 229 genera. Two taxa at Los Cedros have recently been recommended to the IUCN Fungal Red List Initiative (Thamnomyces chocöensis Læssøe and "Lactocollybia" aurantiaca Singer), and we add occurrence data for two others already under consideration (Hygrocybe aphylla Læssøe & Boertm. and Lamelloporus americanus Ryvarden).

CONCLUSIONS

Plants and animals are known to exhibit exceptionally high diversity and endemism in the Chocó bioregion, as the fungi do as well. Our collections contribute to understanding this important driver of biodiversity in the Neotropics, as well as illustrating the importance and utility of such data to conservation efforts.

RESUMEN

Antecedentes: A nivel mundial muchos taxones fúngicos no descritos residen en los trópicos hiper diversos aunque continúan submuestreados. Estas especies están cada vez más amenazadas por la destrucción del hábitat debido a la expansión de la industria extractivista además del cambio climático global y otras amenazas. Los Cedros es una reserva de bosque nublado primario de ~ 5256 ha y se encuentra entre las últimas cuencas hidrográficas no explotadas en la vertiente occidental de los Andes ecuatorianos. Nunca antes se ha realizado un estudio de diversidad micológica en el sitio, lo que significa una oportunidad para documentar hongos en el bosque primario, en hábitat y ubicación subrepresentatadas. El presente estudio recopila información entre el 2008 y 2019 muestreando material sobre todos los sustratos, reportando 1760 colecciones catalogadas y depositadas en el Fungario del QCNE de Ecuador, en su mayoría Agaricales sensu lato y Xylariales; además se documenta la diversidad mediante secuenciación de códigos de barras ITS y fotografía digital, la información está disponible en repositorios públicos digitales (GenBank e iNaturalist).

RESULTADOS

La identificación preliminar indica la presencia de al menos 727 especies únicas de hongos dentro de la Reserva, que representan 4 filos, 17 clases, 40 órdenes, 101 familias y 229 géneros. Recientemente dos taxones en Los Cedros se recomendaron a la Iniciativa de Lista Roja de Hongos de la UICN (Thamnomyces chocöensis Læssøe y "Lactocollybia" aurantiaca Singer) y agregamos datos de presencia de otros dos que ya estaban bajo consideración (Hygrocybe aphylla Læssøe & Boertm. y Lamelloporus americanus Ryvarden).

CONCLUSIONES

Se sabe que plantas y animales exhiben una diversidad y endemismo excepcionalmente altos en la bioregión del Chocó y los hongos no son la excepción. Nuestras colecciones contribuyen a comprender este importante promotor de la biodiversidad en el Neotrópico además de ilustrar la importancia y utilidad de dichos datos para los esfuerzos de conservación.

Expression of EGFR and survivin in ameloblastoma, odontogenic keratocyst and calcifying odontogenic cyst - An immunohistochemical study

Context

Odontogenic lesions have diverse biological behaviour which is characterised by local invasiveness, and a high recurrence rate. EGFR and survivin was found to be involved in the aggressiveness, recurrences and metastasis of a variety of epithelial malignancies.

Aims

To assess and compare the expression of EGFR and survivin in Ameloblastoma (AB), Odontogenic keratocyst (OKC) and Calcifying odontogenic cyst (COC).

Settings and Design

The study's goal was to use immunohistochemistry to assess the qualitative and quantitative expression of EGFR and survivin and to correlate their expression patterns in AB, OKC and COC.

Methods and Material

Study included 30 AB, 15 OKC and 10 COC. All the slides were immunohistochemically analysed for qualitative, quantitative and semi-quantitative data. In each group, the presence of EGFR and survivin was assessed in terms of stain localisation, intensity and percentage of positive cells.

Statistical Analysis Used

Data were analysed using Chi-square test and one-way ANOVA, P value < 0.05 was considered statistically significant.

Results

EGFR positivity was found in all cases. Survivin was found to be 96% positive in AB and 100% positive in OKC and COC. Both EGFR and survivin showed predominant cytoplasmic staining. All the slides that are stained with EGFR are also stained with survivin. The intensity varied significantly between the layers. OKC showed higher immunoreactive scores (IRSs).

Conclusions

The current study provides insight into the role of EGFR and survivin in the pathogenesis of AB, OKC and COC. OKC appears to be more aggressive than ameloblastoma and COC, owing to its higher IRS.

Temporomandibular Disorders Within the Context of Sleep Disorders

This paper provided an overview of the knowledge on the relationship between temporomandibular disorders (TMDs) and the main sleep conditions and disorders of dental interest, namely, sleep bruxism (SB), sleep apnea, and gastroesophageal reflux disease (GERD). It emerged that although the topic of SB as a possible detrimental factor for the stomatognathic structures has been the most studied, evidence is growing that SB, obstructive sleep apnea, and GERD, all belong to a circle of mutually interacting sleep disorders and conditions that, in turn, may be associated with TMDs. The pathophysiology of the cause-and-effect relationships, if existing, has to be elucidated yet.

Systemic Factors in Temporomandibular Disorder Pain

The science of temporomandibular disorder (TMD) pain and its management has gone through significant changes during the last several decades. The authors strongly feel that the effect of systemic factors influencing TMD pain has been largely overlooked and poorly accounted for, even in established pain-management programs and protocols. The hope is that this article will act as a wake-up call for the pain management community to consider the importance of adequate knowledge of the systemic factors that affect the experience of TMD pain by the patient.

Temporomandibular Joint Disorder Comorbidities

Comorbidity is a distinct additional condition that either existed or exists during the clinical course of a patient afflicted by the condition/entity in question. The clinician attempting to manage temporomandibular joint disorder (TMD) and TMD pain must realize that recognition and management of the comorbidities are essential to the successful management of the same with optimal pain control. When TMD presents with multiple comorbidities, the task for the clinician becomes more complex. It is the hope of the authors that this condensed version of TMD-associated comorbidities acts as a primer for understanding the significance of the same in pain management.

Temporomandibular Disorders: Implications in Restorative Dentistry and Orthodontics

Over the past several decades, the science of restorative/reconstructive dentistry and orthodontics has evolved tremendously, following sound principles passed down from robust literature and scientific rationale. These principles have been solid and instrumental in enhancing dentistry, from a single tooth restoration to complex full-mouth rehabilitations. However, it must be noted that some of the principles and philosophies followed over these decades have been questioned based on the advances in science, technology, and evidence-based medicine. The scenario became complex when clinicians were faced with the question of guidance for optimum joint and muscle health as related to restorative dentistry and orthodontics.

Temporomandibular Disorders and Dental Occlusion: What Do We Know so Far?

Throughout the recorded history in the literature of temporomandibular disorders (TMD) there have been a variety of opinions as to its primary cause. Those supporting an occlusal basis of TMD opined that occlusal dysfunction is either the primary cause for or a significant etiopathogenic factor in the causation of TMD. Most of the current literature, however, points to evidence in another direction and questions the causal role of occlusion and occlusal disharmony in TMD etiopathogenesis. Recognition of this evidence-based literature is paramount in eliminating and preventing the chances of overtreatment of patients with TMD.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Role of primary cilia and Hedgehog signaling in craniofacial features of Ellis-van Creveld syndrome

Ellis-van Creveld syndrome (EvC) is an autosomal recessive genetic disorder involving pathogenic variants of EVC and EVC2 genes and classified as a ciliopathy. The syndrome is caused by mutations in the EVC gene on chromosome 4p16, and EVC2 gene, located close to the EVC gene, in a head-to-head configuration. Regardless of the affliction of EVC or EVC2, the clinical features of Ellis-van Creveld syndrome are similar. Both these genes are expressed in tissues such as, but not limited to, the heart, liver, skeletal muscle, and placenta, while the predominant expression in the craniofacial tissues is that of EVC2. Biallelic mutations of EVC and EVC2 affect Hedgehog signaling and thereby ciliary function, crucial factors in vertebrate development, culminating in the phenotypical features characteristic of EvC. The clinical features of Ellis-van Creveld syndrome are consistent with significant abnormalities in morphogenesis and differentiation of the affected tissues. The robust role of primary cilia in histodifferentiation and morphodifferentiation of oral, perioral, and craniofacial tissues is becoming more evident in the most recent literature. In this review, we give a summary of the mechanistic role of primary cilia in craniofacial development, taking Ellis-van Creveld syndrome as a representative example.

Bilateral intraoral traumatic neuroma: Case report of a diagnostic challenge

Oral traumatic neuromas (TrNs) are relatively rare lesions and they originate from a damaged nerve. They present a diagnostic challenge, due to the complex clinical features that may mimic odontogenic, musculoskeletal, and other neuropathic pain conditions. We describe an interesting and challenging case of painful bilateral intraoral lesions in a 56-year-old South Indian female patient who presented with clinical features consistent with TrN lesions bilaterally, in relation to different branches of the trigeminal nerve. The patient had undergone numerous aggressive dental treatments and interventions over the past three decades, with little or no pain relief. Topical treatment with lidocaine gel utilizing a custom-made neurosensory stent rendered the patient significant and sustained pain relief.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.

Facial pain and trigeminal neuralgia secondary to metastasis: A case report

BACKGROUND AND OVERVIEW

Trigeminal neuralgia due to a metastatic lesion is a relatively rare occurrence. These cases pose a diagnostic challenge for the clinician due to a complex clinical presentation.

CASE DESCRIPTION

The authors describe the case of a 65-year-old woman with left-sided facial pain and occasional numbness. The patient also reported autonomic features associated with facial pain, facial muscular weakness, and hearing and visual impairment. The patient's history of breast cancer, for which she was receiving treatment for bone metastasis, warranted diagnostic imaging. Magnetic resonance imaging with and without contrast was performed and revealed a possible metastatic lesion.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Unusual clinical features must be identified, and prompt appropriate imaging is instrumental in making at an accurate diagnosis and management plan.

Occipital Neuralgia and Its Management: An Overview

Background

Greater and lesser occipital neuralgias are primary neuralgias that are relatively uncommon, where the pain is felt in the distribution of these nerves.

Objective

This review paper was intended to describe the features and management of occipital neuralgia in the context of a challenging case.

Material and Methods

We looked at succinct literature from the past 30 years. We compared the features of our challenging case given in the current literature. In addition, an overview of the current literature is provided.

Results

The case, although proved to be a diagnostic challenge, we were able to reach a conclusion and render the patient almost complete pain relief by conservative management modalities. It proved to be a rare presentation of occipital neuralgia with unusual pain distribution, and we are able to describe a literature-based explanation for this entity to be a diagnostic and management challenge.

Conclusion

Primary headaches, i'n general, are a group of headache disorders that require exquisite diagnostic skills. The clinical history is a key factor when making an accurate diagnosis, and to establish an appropriate management plan.

Monckeberg's Medial Sclerosis as a Cause for Headache and Facial Pain

PURPOSE OF REVIEW

Mönckeberg's medial sclerosis (MMS) is a chronic, non-inflammatory degenerative condition affecting primarily the tunica media of muscular arteries resulting in their calcification. The purpose of this comprehensive review is to describe MMS as it appears in the literature, in the context of headache and facial pain. Understanding the etiopathology, the associated conditions, and the differential diagnoses is important in managing MMS.

RECENT FINDINGS

Management of MMS primarily depends upon identification of its associated conditions and their treatment. Due to the rare incidence and inadequate literature on MMS presenting with headaches, the diagnosis of the pain and the entity itself is challenging. MMS is characterized by associated systemic conditions and absence of inflammatory markers. It can mimic giant cell arteritis (GCA) and other pain entities. An interdisciplinary approach involving appropriate specialties is recommended.

Orofacial manifestations of rheumatoid arthritis and systemic lupus erythematosus: a narrative review

Both rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are classified as autoimmune diseases, where the body's own immune response causes it to attack the host tissues, as if the latter were antigens. RA is the most common autoimmune disease that affects joints. The clinical diagnosis of RA is based on the history and examination, integrated with laboratory tests including blood tests on inflammatory markers, serology, and imaging. There are no diagnostic criteria, but there are classification criteria. SLE affects most major organ systems in the body. The diagnosis of SLE relies on the constellation of characteristic symptoms, signs, and laboratory findings in the appropriate clinical context and after excluding other reasonable diagnoses. Epidemiologically, both conditions show a definitive female predilection. The focus of this review article is epidemiology, and the major clinical features with an emphasis on the orofacial manifestations. The relevant clinical points for the dental practitioner area summarized.

Nummular Headache - a Case Report of a Rare Entity

PURPOSE OF REVIEW

The purpose of this manuscript is to shed light on systematic work-up of a diagnostic challenge such as nummular headache (NH), and to summarize the relevant literature on NH.

RECENT FINDINGS

The specific nature of the shape of the pain site is usually characteristic of NH. Multiple modalities of investigation including succinct imaging are necessary to successfully rule out other similar conditions. A 26-year-old female patient of Asian-Indian origin presented to the clinic with the chief complaint of chronic persistent left parietal headache for more than 10 years, which has been worsening over the past few days with no specific identifiable trigger. The diagnosis of nummular headache is challenging and confusing due to the rare occurrence and inadequate references in the literature. Appropriate imaging was done, which revealed no pathology that could explain the headache presentation. These findings are consistent with our diagnosis of nummular headache, and helped in the successful management of the case.

Expression, purification and metal utilization of recombinant SodA from Borrelia burgdorferi

Borrelia are microaerophilic spirochetes capable of causing multisystemic diseases such as Lyme disease and Relapsing Fever. The ubiquitous Fe/Mn-dependent superoxide dismutase (SOD) provides essential protection from oxidative damage by the superoxide anion. Borrelia possess a single SOD enzyme - SodA that is essential for virulence, providing protection against host-derived reactive oxygen species (ROS). Here we present a method for recombinant expression and purification of Borrelia burgdorferi SodA in E. coli. Metal exchange or insertion into the Fe/Mn-SOD is inhibited in the folded state. We therefore present a method whereby the recombinant Borrelia SodA binds to Mn under denaturing conditions and is subsequently refolded by a reduction in denaturant. SodA purified by metal affinity chromatography and size exclusion chromatography reveals a single band on SDS-PAGE. Protein folding is confirmed by circular dichroism. A coupled enzyme assay demonstrates SOD activity in the presence of Mn, but not Fe. The apparent molecular weight determined by size exclusion corresponds to a dimer of SodA; a homology model of dimeric SodA is presented revealing a surface Cys distal to the dimer interface. The method presented of acquiring a target metal under denaturing conditions may be applicable to the refolding of other metal-binding proteins.

Use of masseteric and deep temporal nerve blocks for reduction of mandibular dislocation

A patient presented with a unilateral dislocated condyle that was resistant to reduction by simple manual manipulation because of elevator muscle spasm and severe muscle and temporomandibular joint pain. A technique involving a masseteric nerve block and a temporal nerve block was used, allowing a quick, safe, and minimally painful reduction. The method used for delivering these nerve blocks is described here.

Risk for contralateral breast cancer among carriers of the CHEK2*1100delC mutation in the WECARE Study

The protein encoded by the CHEK2 gene is involved in cellular repair of DNA damage. The truncating mutation, CHEK2^*1100delC, seems to increase the risk for breast cancer. We investigated whether the CHEK2^*1100delC mutation carrier status increases the risk for asynchronous contralateral breast cancer (CBC) and whether it interacts with radiation therapy (RT) or chemotherapy in regard to CBC risk. The germline mutation frequency was assessed in 708 women with CBC and 1395 women with unilateral breast cancer (UBC) in the Women's Environment, Cancer and Radiation Epidemiology (WECARE) Study whose first primary breast cancer was diagnosed before age 55 years and during 1985–1999. Seven women with CBC (1.0%) and 10 women with UBC (0.7%) were CHEK2^*1100delC variant carriers (rate ratio (RR)=1.8, 95% confidence interval (CI)=0.6–5.4 for CBC vs UBC). Carriers who received RT for their first breast cancer, compared with non-carriers not treated with RT, had an RR of developing CBC of 2.6 (95% CI=0.8–8.7). We found no significant associations between the CHEK2^*1100delC mutation and CBC overall or among those treated with RT. However, the sampling variability was such that modest increases in risk could not be excluded. Nonetheless, because this is a rare mutation, it is unlikely to explain a major fraction of CBC in the population.

Systems biological and mechanistic modelling of radiation-induced cancer

This paper summarises the five presentations at the First International Workshop on Systems Radiation Biology that were concerned with mechanistic models for carcinogenesis. The mathematical description of various hypotheses about the carcinogenic process, and its comparison with available data is an example of systems biology. It promises better understanding of effects at the whole body level based on properties of cells and signalling mechanisms between them. Of these five presentations, three dealt with multistage carcinogenesis within the framework of stochastic multistage clonal expansion models, another presented a deterministic multistage model incorporating chromosomal aberrations and neoplastic transformation, and the last presented a model of DNA double-strand break repair pathways for second breast cancers following radiation therapy.

Haplotype Sharing Analysis Using Mantel Statistics

OBJECTIVE

The potential value of haplotypes has attracted widespread interest in the mapping of complex traits. Haplotype sharing methods take the linkage disequilibrium information between multiple markers into account, and may have good power to detect predisposing genes. We present a new approach based on Mantel statistics for spacetime clustering, which is developed in order to improve the power of haplotype sharing analysis for gene mapping in complex disease.

METHODS

The new statistic correlates genetic similarity and phenotypic similarity across pairs of haplotypes for case-only and case-control studies. The genetic similarity is measured as the shared length between haplotypes around a putative disease locus. The phenotypic similarity is measured as the mean-corrected cross-product based on the respective phenotypes. We analyzed two tests for statistical significance with respect to type I error: (1) assuming asymptotic normality, and (2) using a Monte Carlo permutation procedure. The results were compared to the chi(2) test for association based on 3-marker haplotypes.

RESULTS

The results of the type I error rates for the Mantel statistics using the permutational procedure yielded pointwise valid tests. The approach based on the assumption of asymptotic normality was seriously liberal.

CONCLUSION

Power comparisons showed that the Mantel statistics were better than or equal to the chi(2) test for all simulated disease models.

Evolution of the simulated data problem

The simulated data problem was designed via an interactive process by the Simulation Problem Organizing Committee and the selected data simulators. Based on discussions at the previous Genetic Analysis Workshop, many of the features of previous simulation problems, such as a complex disease, genome scan, and replication, were retained and in addition, a population genetics model was used to generate the simulated genes. We describe the process that was used to structure the problem and summarize the discussions about many of the scientific issues that were considered.

Genome scan of complex traits by haplotype sharing correlation

We introduce a haplotype-sharing correlation in founder haplotypes for use in genome scanning. The method evaluates the correlation between phenotype similarity and haplotype similarity at each candidate location. When applied to Genetic Analysis Workshop 12 simulated data for disease status, age at onset, and quantitative traits Q1-Q5, we found highly significant signals near four simulated disease loci in genome scans using microsatellite marker data and highly significant gene effects in three casual genes using sequence data.

Bayes estimates of haplotype effects

We describe a Markov chain Monte Carlo implementation of a Bayesian approach to estimating associations of a trait with a large set of haplotypes recently introduced by Clayton and Jones [Am J Hum Genet 65:1161-9, 2000]. The model uses the length of the longest segment in common between any two haplotypes to define the prior correlation structure for the set of haplotype effects, using an intrinsic autocorrelation model. When applied to the Genetic Analysis Workshop 12 data for trait Q1, we found highly significant variation between haplotypes, using either a structured or unstructured covariance matrix.

International Genetic Epidemiology Society: commentary on Darkness in El Dorado by Patrick Tierney

The International Genetic Epidemiology Society (IGES) has examined the charges against James V. Neel and his colleagues contained in the recently published book by Patrick Tierney entitled Darkness in El Dorado: How Scientists and Journalists Devastated the Amazon (W.W. Norton, 2000). The book implicates Neel in causing or promoting an epidemic of measles among the Yanomamö Indians of Venezuela in 1968 leading to "hundreds if not thousands" of deaths by using a "dinosaur" vaccine (Edmonston B) as a deliberate "experiment" to test his "eugenic" theories. Tierney also attempts to link this research, funded by the Atomic Energy Commission (AEC), with a broader tapestry of human radiation experiments. To investigate these serious charges, the IGES undertook a thorough examination of most source documents referenced in Tierney's book, Neel's field logs, notes, first-hand reports, contemporary writings, film sound tracks, etc., and conducted interviews with many relevant persons. The IGES finds that these allegations are false. Neel was not a eugenicist and was in fact highly critical of both the scientific basis of eugenics and its coercive social policies. In this regard, Tierney has grossly misrepresented Neel's views on a wide range of social implications of modern civilization for the long-term health of the gene pool. Far from causing an epidemic of measles, Neel did his utmost to protect the Yanomamö from the ravages of the impending epidemic by a vaccination program using a vaccine that was widely used at the time and administered in an appropriate manner. There was nothing experimental about the vaccination program, which in fact severely hindered the primary scientific objectives of the expedition. Although the research was funded in large part by the AEC, there was no element of radiation research and the work had no connection with the ethical abuses that have been reported from AEC-sponsored radiation research, such as studies of heavy isotopes. Neel's seminal contributions to a broad range of topics in human genetics have been extensively chronicled elsewhere. His research on the Yanomamö in particular has provided unique insights into the evolutionary biology of our species, the role of sociocultural practices, such as kinship relationships and selective pressures in shaping the genetic diversity of primitive population isolates, as well as the general picture of health in such populations. The IGES decries the damage done to the reputation of one of its founders and its first President and the misperception this book may have caused about the conduct of research in genetic epidemiology. Ethical issues about scientific research in primitive populations deserve serious and wide discussion, but the IGES condemns the gross misrepresentation of the facts and demonization of the principal characters in this book.

The role of interacting determinants in the localization of genes

We describe the potential gains in power for localizing disease genes that can be obtained by allowing for interactions with environmental agents or other genes. The focus is on linkage and association methods in nuclear families with dichotomous phenotypes. A logistic model incorporating various main effects and interactions is used for penetrance, but similar methods apply to censored age-at-onset or continuous phenotypes. We begin by discussing the influence of gene-environment interactions in segregation analysis, illustrated with analysis of smoking as a modifying factor for lung cancer. We then discuss a number of approaches to linkage analysis-model-free and model-based(including generalized estimating equations) incorporating interactions with environmental factors and other genes, either candidate genes or linked loci. We find that a test of heterogeneity in IBD sharing probabilities across strata defined by sharing of environmental factors can offer greater power for detecting linkage than the simple mean test, provided the interaction effect is sufficiently strong; we explore the conditions under which this gain in power occurs. Finally, we describe approaches for testing association and disequilibrium involving interactions, utilizing case-control, case-parent, and pedigree-based approaches. A technical problem that must be addressed in many analyses is the effect of missing data on environmental covariates; we use multiple imputation in an analysis of lung cancer segregation to illustrate an approach to this problem.

Counter-matching in studies of gene-environment interaction: efficiency and feasibility

The interest in studying gene-environment interaction is increasing for complex diseases. However, most methods of detecting gene-environment interactions may not be appropriate for the study of interactions involving rare genes (G:) or uncommon environmental exposures (E:), because of poor statistical power. To increase this power, the authors propose the counter-matching design. This design increases the number of subjects with the rare factor without increasing the number of measurements that must be performed. In this paper, the efficiency and feasibility (required sample sizes) of counter-matching designs are evaluated and discussed. Counter-matching on both G: and E: appears to be the most efficient design for detecting gene-environment interaction. The sensitivity and specificity of the surrogate measures, the frequencies of G: and E:, and, to a lesser extent, the value of the interaction effect are the most important parameters for determining efficiency. Feasibility is also more dependent on the exposure frequencies and the interaction effect than on the main effects of G: and E: Although the efficiency of counter-matching is greatest when the risk factors are very rare, the study of such rare factors is not realistic unless one is interested in very strong interaction effects. Nevertheless, counter-matching appears to be more appropriate than most traditional epidemiologic methods for the study of interactions involving rare factors.

The effects of ambient air pollution on school absenteeism due to respiratory illnesses

We investigated the relations between ozone (O3), nitrogen dioxide (NO2), and respirable particles less than 10 microm in diameter (PM10) and school absenteeism in a cohort of 4th-grade school children who resided in 12 southern California communities. An active surveillance system ascertained the numbers and types of absences during the first 6 months of 1996. Pollutants were measured hourly at central-site monitors in each of the 12 communities. To examine acute effects of air pollution on absence rates, we fitted a two-stage time-series model to the absence count data that included distributed lag effects of exposure adjusted for long-term pollutant levels. Short-term change in O3, but not NO2 or PM10, was associated with a substantial increase in school absences from both upper and lower respiratory illness. An increase of 20 ppb of O3 was associated with an increase of 62.9% [95% confidence interval (95% CI) = 18.4-124.1%] for illness-related absence rates, 82.9% (95% CI = 3.9-222.0%) for respiratory illnesses, 45.1% (95% CI = 21.3-73.7%) for upper respiratory illnesses, and 173.9% (95% CI = 91.3-292.3%) for lower respiratory illnesses with wet cough. The short-term effects of a 20-ppb change of O3 on illness-related absenteeism were larger in communities with lower long-term average PM10 [223.5% (95% CI = 90.4-449.7)] compared with communities with high average levels [38.1% (95% CI = 8.5-75.8)]. Increased school absenteeism from O3 exposure in children is an important adverse effect of ambient air pollution worthy of public policy consideration.

Genetic epidemiology with a capital "E"

Three characteristics of genetic epidemiology that distinguish it from its parent disciplines are a focus on population-based research, a focus on the joint effects of genes and the environment, and the incorporation of the underlying biology of the disease into its conceptual models. These principles are illustrated by a review of the genetic epidemiology of breast and ovarian cancer. Descriptive and mechanistic models for the joint effects of genes and "environmental" risk factors such as hormones and reproductive events are compared to illustrate the need to understand the biology. The contribution of population-based research to the development of the evidence for the involvement of major genes, the discovery of BRCA1 and BRCA2, and their characterization is reviewed. Interactions of major susceptibility genes, metabolic genes, and hormones are also discussed. I conclude with some suggestions for future directions for the field, the journal, and the Society, including recent bioethics initiatives. I believe that the Society should reach out more to the epidemiology community and that the journal should shift its emphasis from pure methodology to also include more substantive papers that illustrate these principles.

Performance of Markov chain-Monte Carlo approaches for mapping genes in oligogenic models with an unknown number of loci

Markov chain-Monte Carlo (MCMC) techniques for multipoint mapping of quantitative trait loci have been developed on nuclear-family and extended-pedigree data. These methods are based on repeated sampling-peeling and gene dropping of genotype vectors and random sampling of each of the model parameters from their full conditional distributions, given phenotypes, markers, and other model parameters. We further refine such approaches by improving the efficiency of the marker haplotype-updating algorithm and by adopting a new proposal for adding loci. Incorporating these refinements, we have performed an extensive simulation study on simulated nuclear-family data, varying the number of trait loci, family size, displacement, and other segregation parameters. Our simulation studies show that our MCMC algorithm identifies the locations of the true trait loci and estimates their segregation parameters well-provided that the total number of sibship pairs in the pedigree data is reasonably large, heritability of each individual trait locus is not too low, and the loci are not too close together. Our MCMC algorithm was shown to be significantly more efficient than LOKI (Heath 1997) in our simulation study using nuclear-family data.

Morbid hypocalcemia associated with phosphate enema in a six-week-old infant

A 6-week-old premature infant who was born at 29 weeks of gestation presented to the emergency department with a several-hour history of stiffness and increased alarms on his apnea monitor at home. On arrival he was noted to have generalized seizures, apnea, and bradycardia. He was intubated and required cardiopulmonary resuscitation including chest compressions and medications. After stabilization he was transferred to the neonatal intensive care unit for further management. His initial laboratory tests revealed a serum calcium level of 2.4 mg/dL (normal range: 8.4-10.2 mg/dL) and a serum phosphorus level of 28.5 mg/dL (normal range: 2.4-4.5 mg/dL). During the first week of admission, the infant's mother reported that she had administered a full pediatric Fleets enema (CB Fleet Company Inc, Lynchburg, VA) to him. The infant was discharged after 12 days of hospitalization. Anticipatory guidance on the stool patterns and behavior of infants can prevent misconceptions about constipation that are especially prevalent in new parents. Proper management of constipation, should it arise, should be addressed with all parents at early well-child visits to avoid hazardous complications of treatments. hypocalcemia, seizures, premature infants, enema.

Multistage sampling for disease family registries

BACKGROUND

The objectives of a family-based disease registry range from characterizing measured genetic factors and gene-environment interaction effects to detecting novel susceptibility genes. Gathering complete information on exposure and disease status in all family members for a sample of affected subjects (probands) to address these diverse objectives would be prohibitively expensive.

METHODS

Multistage sampling can be used to design an efficient family-based disease registry. At each stage, the probands are classified on the basis of previously collected data, and a subsample is selected for more detailed observation. The design can be optimized to minimize the variance of any of the model parameter estimates, subject to a constraint on the total sample size.

RESULTS

We describe the basic statistical theory and its application to a four-stage sampling scheme proposed for the Cooperative Family Registry for Epidemiologic Studies of Colorectal Cancer at the University of Southern California.

Family-based association studies

We review case-control designs for studying gene associations in which relatives of case patients are used as control subjects. These designs have the advantage that they avoid the problem of population stratification that can lead to spurious associations with noncausal genes. We focus on designs that use sibling, cousin, or pseudosibling controls, the latter formed as the set of genotypes not transmitted to the case from his or her parents. We describe a common conditional likelihood framework for use in analyzing data from any of these designs and review what is known about the validity of the various design and analysis combinations for estimating the genetic relative risk. We also present comparisons of efficiency for each of the family-based designs relative to the standard population-control design in which unrelated controls are selected from the source population of cases. Because of overmatching on genotype, the use of sibling controls leads to estimates of genetic relative risk that are approximately half as efficient as those obtained with the use of population controls, while relative efficiency for cousin controls is approximately 90%. However, we find that, for a rare gene, the sibling-control design can lead to improved efficiency for estimating a G x E interaction effect. We also review some restricted designs that can substantially improve efficiency, e.g., restriction of the sample to case-sibling pairs with an affected parent. We conclude that family-based case-control studies are an attractive alternative to population-based case-control designs using unrelated control subjects.

Cohort studies for characterizing measured genes

We describe the advantages of using established cohort studies that have collected blood samples to investigate the role of genes in the etiology of cancer. These studies include the cost-efficiency and reliability of nested case-control substudies from the cohort for exploration of gene-disease associations and gene-environment interactions as well as gene penetrance. Also, the cohort may serve as a well-defined "mini-population" from which to study population stratification and molecular markers of ethnicity. We conclude that cohort studies can play a significant role in assessing the role of genetic markers for common tumors or multiple cancer sites.

Study-design issues in the development of the University of Southern California Consortium's Colorectal Cancer Family Registry

The University of Southern California Consortium is a participating center in the National Cancer Institute's Collaborative Family Registry for Colorectal Cancer Studies (CFRCCS). Because data collection takes time, money, and effort, all of which are in short supply, we first defined our research objectives and then attempted to design our registry to enable us to address these objectives in an efficient manner. We decided on a family-based design, and our objectives are to characterize cloned genes that are generally accepted causes of colorectal cancer, to assess putative candidate genes, to map new genes, and to conduct prevention trials in high-risk subjects. For the gene characterization objectives, our primary aim is to estimate gene frequency and penetrance, with a secondary aim to investigate factors that may affect penetrance (allele-specific effects plus gene-gene and gene-environment interactions). We describe a multiple-stage design to select families into the registry. After a family is selected into the registry, we collect questionnaire data and blood samples on selected subjects only, and we tailor data collection decisions to each family (given who is affected and who is available) to optimize power per unit effort and cost. We also discuss practical decisions faced by our registry, including 1) defining a reference period for use in questionnaires; 2) deciding whether or not to establish cell lines and, if so, on whom; and 3) determining which cases should be tested for microsatellite instability. Finally, we address the appropriate use of data derived from high-risk clinics, within more broadly defined, population-based research.