Soccer, neurotrauma and amyotrophic lateral sclerosis: is there a connection?

Raw Water and ALS: A Unifying Hypothesis for the Environmental Agents Involved in ALS

Different studies identified the presence of several altered genes in familial and sporadic amyotrophic lateral sclerosis (ALS) forms. The experimental data, together with the epidemiological data, would seem to suggest the existence of molecular mechanisms (e.g., axonal transport) related to these genes, together with a susceptibility of the same genes to certain environmental factors that would therefore suggest an impact of the environment on the etiopathogenesis of ALS. In our review, we considered the most relevant environmental clusters around the world, collecting different hypotheses and underlining common environmental factors among the different clusters. Moreover, further epidemiological data identified a higher risk of ALS in professional athletes and, in particular, in soccer and football players. Despite this increased risk of ALS highlighted by the epidemiological evidence in aforementioned sports, the mechanisms remain unclear. At last, the use of raw water has been associated with ALS risk. The aim of the present review is to characterize a possible relationship between these clusters, to be explored in the context of the interaction between genetic and environmental factors on the etiopathogenesis of ALS.

A systematic review on the risk of neurodegenerative diseases and neurocognitive disorders in professional and varsity athletes

Objective

The aim of this systematic review (SR) was to gather all available epidemiological evidence on former participation in any type of sport, at a professional and varsity level, as a potential risk factor for neurodegenerative diseases (NDs) and neurocognitive disorders (NCDs).

Design

Systematic searches were performed on PubMed, the Cochrane databases, and the ISI Web of Knowledge databases. Included studies were assessed using the NOS checklist.

Eligibility criteria for selecting studies

All epidemiological studies reporting data on the possible association between a clinical diagnosis of amyotrophic lateral sclerosis (ALS)/motor neuron disease (MND), dementia or mild cognitive impairment (MCI), Parkinson’s disease (PD), chronic traumatic encephalopathy (CTE) at any stage and with any clinical pattern and the former participation in any types of sport at a varsity and professional level were included.

Results

Data from the 17 included studies showed a higher frequency of NDs and NCDs in former soccer and American football players. Updating the previous SR confirmed a higher frequency of ALS/MND in former soccer players. Data reported a significantly higher risk of dementia/AD in former soccer players, and of MCI in former American football players. Results also showed a significantly higher risk of PD in former soccer and American football players, and a significantly higher risk of CTE in former boxers and American football players.

Summary/conclusions

This SR confirmed a higher risk of NDs and NCDs in former professional/varsity athletes. However, the pathological mechanisms underlying this association remain unclear, and further high-quality studies should be performed to clarify whether the association could be sport specific.

Skeletal Muscle Metabolism: Origin or Prognostic Factor for Amyotrophic Lateral Sclerosis (ALS) Development?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive and selective loss of motor neurons, amyotrophy and skeletal muscle paralysis usually leading to death due to respiratory failure. While generally considered an intrinsic motor neuron disease, data obtained in recent years, including our own, suggest that motor neuron protection is not sufficient to counter the disease. The dismantling of the neuromuscular junction is closely linked to chronic energy deficit found throughout the body. Metabolic (hypermetabolism and dyslipidemia) and mitochondrial alterations described in patients and murine models of ALS are associated with the development and progression of disease pathology and they appear long before motor neurons die. It is clear that these metabolic changes participate in the pathology of the disease. In this review, we summarize these changes seen throughout the course of the disease, and the subsequent impact of glucose–fatty acid oxidation imbalance on disease progression. We also highlight studies that show that correcting this loss of metabolic flexibility should now be considered a major goal for the treatment of ALS.

Trauma and amyotrophic lateral sclerosis: a systematic review and meta-analysis

Background: Trauma especially head trauma is considered a potential risk factor of amyotrophic lateral sclerosis (ALS), but their association has not been well established. We aimed to determine the association of prior trauma with ALS risk. Methods: This study was performed according to the Meta-Analysis of Observational Studies in Epidemiology guideline to assess related literatures, and a random-effects model was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Results: Twenty-nine eligible articles involving 18,390 cases and 6,519,391 controls were included in this meta-analysis. The results showed that trauma was associated with an increased risk of ALS (pooled OR = 1.51, 95% CI: 1.32-1.73). Besides, patients with trunk trauma, head trauma and lower limb trauma had an increased risk of ALS, whereas no evidence suggested that upper limb trauma and spine trauma could increase ALS risk. Considering the number of traumatic events, the association between trauma and ALS risk was significant for patients with repeated trauma events (pooled OR = 1.21, 95% CI: 1.07-1.38). The results showed that individuals with a history of trauma within 5 years were more likely to be diagnosed with ALS (pooled OR = 1.84, 95% CI: 1.56-2.17). Importantly, both old trauma and very old trauma were found to be associated with an increased risk of ALS (pooled OR = 1.24, 95% CI: 1.12-1.38; pooled OR = 1.28, 95% CI: 1.10-1.49; respectively). Conclusions: This meta-analysis indicated that trauma could increase ALS risk, which may be applied for the clinicians to tailor targeted treatment regimens and make prophylactic strategies for ALS in traumatic patients.

Risk factors for amyotrophic lateral sclerosis: A regional United States case-control study

Most amyotrophic lateral sclerosis (ALS) cases are considered sporadic, without a known genetic basis, and environmental exposures are thought to play a causal role. To learn more about sporadic ALS etiology, we recruited n = 188 ALS patients from northern New England and Ohio and matched controls 2:1 from the general population of the same regions. Questionnaires evaluated the association between a variety of lifestyle, behavioral (ie, hobbies and activities), and occupational factors and the risk of ALS, including the duration of time between exposure and ALS onset, and exposure frequency. Head trauma was associated with increased ALS risk (adjusted odds ratio [OR] 1.60 95% confidence interval [CI] 1.04‐2.45), with significantly greater effects for injuries occurring 10 or more years prior to symptom onset (P = .037). ALS risk was increased for those reporting severe electrical burns (adjusted OR 2.86, 95% CI 1.37‐6.03), with odds ratios highest for burns after age 30 (OR 3.14), and for burns 10 or more years prior to symptom onset (OR 3.09). Hobbies involving lead were the most strongly associated with ALS risk (adjusted OR 2.92, 95% CI 1.45‐5.91). Exposures to lead 20 or more years prior to diagnosis had larger effect sizes compared to those occurring more recently. Holding a job in mechanics, painting, or construction was associated with ALS. The identification of these specific environmental factors associated with ALS highlight the need for future prospective and laboratory studies to assess causality, biological mechanisms, and find prevention or treatment opportunities.

Transforming growth factor beta 1 signaling is altered in the spinal cord and muscle of amyotrophic lateral sclerosis mice and patients

Gender differences characterize amyotrophic lateral sclerosis (ALS). Because ALS patients have increased circulating levels of transforming growth factor beta 1 (TGFB1), here we analyzed gender and disease progression-related modification of TGFB1 and its related signaling molecules in the spinal cord and skeletal muscle of ALS mice and in muscle biopsies from sporadic ALS patients. At presymptomatic stage, Tgfb1 mRNA expression is reduced in the mouse spinal cord but is increased selectively in the male skeletal muscle. At symptomatic stage, it is induced both in the mouse spinal cord and muscle, as well as in the muscle of ALS patients. Tgfbr2 levels are induced only in the mouse spinal cord. Smad2 and Smad4 mRNAs are decreased in the mouse spinal cord and muscle, but SMAD2 protein levels are augmented selectively in the male mouse muscle. Smad3 mRNA and SMAD3 protein are increased in the mouse muscle. The expression of genes controlled by TGFB1 in the muscle (Pax7, Collagen1a1, and Fibronectin) are reduced both in male and female ALS mice at symptomatic stage. Thus, TGFB1 modulation may serve as a novel therapeutic target for ALS.

Contact Sports as a Risk Factor for Amyotrophic Lateral Sclerosis: A Systematic Review

STUDY DESIGN

Systematic review.

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease, ultimately resulting in paralysis and death. The condition is considered to be caused by a complex interaction between environmental and genetic factors. Although vast genetic research has deciphered many of the molecular factors in ALS pathogenesis, the environmental factors have remained largely unknown. Recent evidence suggests that participation in certain types of sporting activities are associated with increased risk for ALS.

OBJECTIVE

To test the hypothesis that competitive sports at the highest level that involve repetitive concussive head and cervical spinal trauma result in an increased risk of ALS compared with the general population or nonsport controls.

METHODS

Electronic databases from inception to November 22, 2017 and reference lists of key articles were searched to identify studies meeting inclusion criteria.

RESULTS

Sixteen studies met the inclusion criteria. Sports assessed (professional or nonprofessional) included soccer (n = 5), American football (n = 2), basketball (n = 1), cycling (n = 1), marathon or triathlon (n = 1), skating (n = 1), and general sports not specified (n = 11). Soccer and American football were considered sports involving repetitive concussive head and cervical spinal trauma. Professional sports prone to repetitive concussive head and cervical spinal trauma were associated with substantially greater effects (pooled rate ratio [RR] 8.52, 95% CI 5.18-14.0) compared with (a) nonprofessional sports prone to repetitive concussive head and cervical spinal trauma (pooled RR 0.60, 95% CI 0.12-3.06); (b) professional sports not prone to repetitive head and neck trauma (pooled RR 1.35, 95% CI 0.67-2.71); or (c) nonprofessional sports not prone to repetitive concussive head and cervical spinal trauma (pooled RR 1.17, 95% CI 0.79-1.71).

CONCLUSIONS

Our review suggests that increased susceptibility to ALS is significantly and independently associated with 2 factors: professional sports and sports prone to repetitive concussive head and cervical spinal trauma. Their combination resulted in an additive effect, further increasing this association to ALS.

Theta burst stimulation to characterize changes in brain plasticity following mild traumatic brain injury: A proof-of-principle study

PURPOSE

Recent studies investigating the effects of mild traumatic brain injury (mTBI) suggest the presence of unbalanced excitatory and inhibitory mechanisms within primary motor cortex (M1). Whether these abnormalities are associated with impaired synaptic plasticity remains unknown.

METHODS

The effects of continuous theta burst stimulation (cTBS) on transcranial magnetic stimulation-induced motor evoked potentials (MEPs) were assessed on average two weeks and six weeks following mTBI in five individuals.

RESULTS

The procedure was well-tolerated by all participants. Continuous TBS failed to induce a significant reduction of MEP amplitudes two weeks after the injury, but response to cTBS normalized six weeks following injury, as a majority of patients became asymptomatic.

CONCLUSIONS

These preliminary results suggest that cTBS can be used to assess M1 synaptic plasticity in subacute phase following mTBI and may provide insights into neurobiological substrates of symptoms and consequences of mTBI.

Physical activity, and physical activity related to sports, leisure and occupational activity as risk factors for ALS: A systematic review

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is considered a multifactorial, multisystem neurodegenerative disease due to an interaction between environmental and genetic factors. This systematic review aims at gathering all available evidence on the association between physical activity (PA) and the risk of ALS.

METHODS

Relevant literature published up to January 2015 was gathered through structured searches on Medline, The Cochrane Library, and the ISI Web of Science databases. Studies considering any type of PA as the main exposure and a diagnosis of ALS or motor neuron disease were selected. Data were extracted in standardized forms, and the quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS).

RESULTS

Bibliographic searches yielded 3168 records. Nineteen case control studies and 7 cohort studies met the inclusion criteria, and were included in the analysis. Evidence on cumulative measures of PA as a risk factor for ALS remain inconclusive. However, cohort studies report a significantly higher number of cases of ALS in professional soccer and American football players, and a slightly increased risk of ALS in varsity athletes.

The Role of the Craniocervical Junction in Craniospinal Hydrodynamics and Neurodegenerative Conditions

The craniocervical junction (CCJ) is a potential choke point for craniospinal hydrodynamics and may play a causative or contributory role in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, MS, and ALS, as well as many other neurological conditions including hydrocephalus, idiopathic intracranial hypertension, migraines, seizures, silent-strokes, affective disorders, schizophrenia, and psychosis. The purpose of this paper is to provide an overview of the critical role of the CCJ in craniospinal hydrodynamics and to stimulate further research that may lead to new approaches for the prevention and treatment of the above neurodegenerative and neurological conditions.

A Novel Mathematical Approach to Define the Genes/SNPs Conferring Risk or Protection in Sporadic Amyotrophic Lateral Sclerosis Based on Auto Contractive Map Neural Networks and Graph Theory

Background. Complex diseases like amyotrophic lateral sclerosis (ALS) implicate phenotypic and genetic heterogeneity. Therefore, multiple genetic traits may show differential association with the disease. The Auto Contractive Map (AutoCM), belonging to the Artificial Neural Network (ANN) architecture, "spatializes" the correlation among variables by constructing a suitable embedding space where a visually transparent and cognitively natural notion such as "closeness" among variables reflects accurately their associations. Results. In this pilot case-control study single nucleotide polymorphism (SNP) in several genes has been evaluated with a novel data mining approach based on an AutoCM. We have divided the ALS dataset into two dataset: Cases and Control dataset; we have applied to each one, independently, the AutoCM algorithm. Six genetic variants were identified which differently contributed to the complexity of the system: three of the above genes/SNPs represent protective factors, APOA4, NOS3, and LPL, since their contribution to the whole complexity resulted to be as high as 0.17. On the other hand ADRB3, LIPC, and MMP3, whose hub relevancies contribution resulted to be as high as 0.13, seem to represent susceptibility factors. Conclusion. The biological information available on these six polymorphisms is consistent with possible pathogenetic pathways related to ALS.

The anabolic/androgenic steroid nandrolone exacerbates gene expression modifications induced by mutant SOD1 in muscles of mice models of amyotrophic lateral sclerosis

Anabolic/androgenic steroids (AAS) are drugs that enhance muscle mass, and are often illegally utilized in athletes to improve their performances. Recent data suggest that the increased risk for amyotrophic lateral sclerosis (ALS) in male soccer and football players could be linked to AAS abuse. ALS is a motor neuron disease mainly occurring in sporadic (sALS) forms, but some familial forms (fALS) exist and have been linked to mutations in different genes. Some of these, in their wild type (wt) form, have been proposed as risk factors for sALS, i.e. superoxide dismutase 1 (SOD1) gene, whose mutations are causative of about 20% of fALS. Notably, SOD1 toxicity might occur both in motor neurons and in muscle cells. Using gastrocnemius muscles of mice overexpressing human mutant SOD1 (mutSOD1) at different disease stages, we found that the expression of a selected set of genes associated to muscle atrophy, MyoD, myogenin, atrogin-1, and transforming growth factor (TGF)β1, is up-regulated already at the presymptomatic stage. Atrogin-1 gene expression was increased also in mice overexpressing human wtSOD1. Similar alterations were found in axotomized mouse muscles and in cultured ALS myoblast models. In these ALS models, we then evaluated the pharmacological effects of the synthetic AAS nandrolone on the expression of the genes modified in ALS muscle. Nandrolone administration had no effects on MyoD, myogenin, and atrogin-1 expression, but it significantly increased TGFβ1 expression at disease onset. Altogether, these data suggest that, in fALS, muscle gene expression is altered at early stages, and AAS may exacerbate some of the alterations induced by SOD1 possibly acting as a contributing factor also in sALS.

Identifying potential risk factors for developing amyotrophic lateral sclerosis

SUMMARY Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of adult life, characterized by the progressive loss of upper motor neurons in the primary motor cortex and of the spinal and bulbar lower motor neurons. The cause of sporadic cases and of the majority of hereditary cases remains elusive. So far a total of 17 genes or genetic loci of familial ALS have been identified, related to DNA/RNA processing, protein aggregation, membrane trafficking and axonal transport and mitochondrial dysfunction. A large range of environmental factors have also been studied, with inconclusive results, with the possible exception of cigarette smoking. ALS is now considered a complex multifactorial neurodegenerative disorder, but studies analyzing genetic and environmental factors together are still underway.

Modifying effect of arterial hypertension on amyotrophic lateral sclerosis

Given the high oxygen consumption of motor neurons, we sought to assess the frequency and prognostic value of arterial hypertension (affecting brain's oxygen supply) in amyotrophic lateral sclerosis (ALS). We consecutively and prospectively included all ALS patients with regular medical follow-up and documented blood pressure measurements and monitored them until death. Vascular factors diagnosed prior to the onset of motor signs in ALS patients were compared with those in a stratified, age- and gender-matched case-control population. The severity of leukoaraiosis on magnetic resonance imaging (MRI) was blindly assessed. Post mortem examinations were performed when authorized. Compared with controls (n = 408), the 102 ALS patients were significantly more likely to display hypertension (41-57%) and current smoking (15-26%). The number of years of hypertension was associated with survival (HR = 1.04 (1.01-1.07)). In a multivariate analysis, leukoaraiosis severity (HR = 1.214 (1.096-1.344)), current smoking (HR = 1.766 (1.085-2.872)) and low vital capacity (HR = 2.422 (1.266-4.633)) remained independent predictors of survival. Post mortem examinations revealed a greater frequency of leukoaraiosis in ALS patients (p = 0.02). In conclusion, the effect of chronic hypertension on survival might be exerted through abnormal neural perfusion. The higher frequency of recent hypertension in ALS patients may be due to a compensatory increase in blood pressure in response to a lower oxygen supply.

Do RCAN1 proteins link chronic stress with neurodegeneration?

It has long been suspected that chronic stress can exacerbate, or even cause, disease. We now propose that the RCAN1 gene, which can generate several RCAN1 protein isoforms, may be at least partially responsible for this phenomenon. We review data showing that RCAN1 proteins can be induced by multiple stresses, and present new data also implicating psychosocial/emotional stress in RCAN1 induction. We further show that transgenic mice overexpressing the RCAN1-1L protein exhibit accumulation of hyperphosphorylated tau protein (AT8 antibody), an early precursor to the formation of neurofibrillary tangles and neurodegeneration of the kind seen in Alzheimer disease. We propose that, although transient induction of the RCAN1 gene might protect cells against acute stress, persistent stress may cause chronic RCAN1 overexpression, resulting in serious side effects. Chronically elevated levels of RCAN1 proteins may promote or exacerbate various diseases, including tauopathies such as Alzheimer disease. We propose that the mechanism by which stress can lead to these diseases involves the inhibition of calcineurin and the induction of GSK-3β by RCAN1 proteins. Both inhibition of calcineurin and induction of GSK-3β contribute to accumulation of phosphorylated tau, formation of neurofibrillary tangles, and eventual neurodegeneration.

The cyanobacteria derived toxin Beta-N-methylamino-L-alanine and amyotrophic lateral sclerosis

There is mounting evidence to suggest that environmental factors play a major role in the development of neurodegenerative diseases like ALS (Amyotrophic Lateral Sclerosis). The non-protein amino acid beta-N-methylamino-L-alanine (BMAA) was first associated with the high incidence of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) in Guam, and has been implicated as a potential environmental factor in ALS, Alzheimer’s disease, and other neurodegenerative diseases. BMAA has a number of toxic effects on motor neurons including direct agonist action on NMDA and AMPA receptors, induction of oxidative stress, and depletion of glutathione. As a non-protein amino acid, there is also the strong possibility that BMAA could cause intraneuronal protein misfolding, the hallmark of neurodegeneration. While an animal model for BMAA-induced ALS is lacking, there is substantial evidence to support a link between this toxin and ALS. The ramifications of discovering an environmental trigger for ALS are enormous. In this article, we discuss the history, ecology, pharmacology and clinical ramifications of this ubiquitous, cyanobacteria-derived toxin.

An exploratory case-control study on spinal and bulbar forms of amyotrophic lateral sclerosis in the province of Rome

Several environmental and life-style factors reported as possibly associated with ALS have been analysed in the present study, focusing on the two clinical onsets of ALS. A case-control study (77 cases and 185 controls) has been performed in the province of Rome in the period 2005-2006. Increased risks were observed in bulbar cases for former smokers (OR: 4.55, 90% CI 1.72-12.08) and more than 24 pack-years, compared with spinal cases for employment in the construction sector and professional exposure to building materials (OR: 5.27, 90% CI 1.15-24.12) and metals (OR: 2.94, 90% CI 1.20-7.21). Overall and bulbar cases showed an increased risk for consumption of cold cuts and a decreased risk for vegetables intake. Regarding head injuries, differences were observed if the last injury occurred in the age range of 30-40 years, among all (OR: 14.2, 90% CI 1.04-194.42) and bulbar (OR: 17.4, 90% CI 1.70-178.5) cases, and less than 30 years among spinal cases (OR: 7.13, 90% CI 1.34-37.94). Moreover, a risk for a time period of 11-30 years since the last head injury suffered was found in bulbar cases (OR: 3.51, 90% CI 1.03-11.95). Some of the hypothesized risk factors for ALS have been found positively associated in this study, with different patterns between bulbar and spinal ALS.

Amyotrophic lateral sclerosis (ALS): three letters that change the people's life. For ever

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the motor nervous system. It causes progressive and cumulative physical disabilities in patients, and leads to eventual death due to respiratory muscle failure. The disease is diverse in its presentation, course, and progression. We do not yet fully understand the cause or causes of the disease, nor the mechanisms for its progression; thus, we lack effective means for treating this disease. Currently, we rely on a multidisciplinary approach to symptomatically manage and care for patients who have ALS. Although amyotrophic lateral sclerosis and its variants are readily recognized by neurologists, about 10% of patients are misdiagnosed, and delays in diagnosis are common. Prompt diagnosis, sensitive communication of the diagnosis, the involvement of the patient and their family, and a positive care plan are prerequisites for good clinical management. A multidisciplinary, palliative approach can prolong survival and maintain quality of life. Treatment with Riluzole improves survival but has a marginal effect on the rate of functional deterioration, whereas non-invasive ventilation prolongs survival and improves or maintains quality of life. In this Review, we discuss the diagnosis, management, and how to cope with impaired function and end of life on the basis of our experience, the opinions of experts, existing guidelines, and clinical trials. Multiple problems require a multidisciplinary approach including aggressive symptomatic management, rehabilitation to maintain motor function, nutritional support (enteric feeding, gastrostomy), respiratory support (non invasive home ventilation, invasive ventilation, tracheotomy), augmentative communication devices, palliative care, psychological support for both patients and families (because family members so often play a central role in management and care), communication between the care team, the patient and his or her family, and recognition of the clinical and social effects of cognitive impairment. Social, bioethical, and financial issues as well as advance directives should be addressed. A plethora of evidence-based guidelines should be compiled into an internationally agreed guideline of best practice. The multidisciplinary team has changed the history of disease, with still no curative therapy available.

[Exogenous risk factors in sporadic ALS: a review of the literature]

The latest reviews of the literature devoted to the epidemiology of ALS all agree that exogenic risk factors play a role in sporadic ALS. Nevertheless, there is no convincing evidence demonstrating in a reproducible manner an association between an environmental risk factor and ALS. This discordance is mainly explained by methodological skews. Over the last ten years, exogenic factors have been analyzed within the framework of specific lifestyle factors such as place of residence, smoking or not, or certain eating practices. The most recent work suggests that interactions between genetic and environmental factors depend on the age at exposure and the duration of exposure. The objectives of this general review is: to analyze the principal case-control studies, historical cohort studies or mortality studies which looked at the associations between an environmental factor and ALS, to present main results of studies having analyzed lifestyles in relation to one or more exogenic factors, and to discuss the limitations of epidemiologic studies on ALS.

Mechanical stress and formation of protein aggregates in neurodegenerative disorders

Misfolded protein aggregates and inclusion bodies have been associated with various protein conformation disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and prion diseases including bovine spongiform encephalopathy (BSE). Models have been proposed as plausible explanations for the extension and progression of protein aggregates; however, little is known about the initiation process of protein aggregation, particularly in sporadic neurodegenerative diseases. Epidemiological data have suggested a tight association between sporadic neurodegenerative diseases and history of mechanical stresses such as trauma, head injury, and occupational exposures, including professional soccer and boxer's brain that carries histological hallmarks of AD/PD. Here, we propose that mechanical stress is an environmental factor that provokes a disturbance in cellular quality control systems and molecular chaperones that target misfolded proteins. This subsequently initiates protein aggregation and results in sporadic neurodegenerative disorders. Further, continuous and repetitive exposure to environmental mechanical stress, mostly in an unrecognized manner, is inevitable in daily life and thus, it functions as a potential driving force for protein aggregation. In this regard, a recent identification of the fact that an intracellular mechanosensor actually exists may support our notion. Reduction in the mechanical stress in combination with other conventional aspects should facilitate the development of rational therapeutics for these neurodegenerative disorders.

Head injury and amyotrophic lateral sclerosis

Recent data showed that soccer players in Italy had an unusually high risk of amyotrophic lateral sclerosis (ALS) and that repeated head trauma might have contributed to this increase. The authors examined whether head injury was related to ALS risk in a case-control study of 109 New England ALS cases diagnosed in 1993-1996 and 255 matched controls. They also conducted a meta-analysis of the published literature. Overall, ever having experienced a head injury was nonsignificantly associated with a higher ALS risk. When compared with persons without a head injury, a statistically significant ALS risk elevation was found for participants with more than one head injury (odds ratio (OR) = 3.1, 95 percent confidence interval (CI): 1.2, 8.1) and patients who had had a head injury during the past 10 years (OR = 3.2, 95 percent CI: 1.0, 10.2). For participants who had had multiple head injuries with the latest occurring in the past 10 years, risk was elevated more than 11-fold. The meta-analysis also indicated a moderately elevated risk of ALS among persons with previous head injuries (OR = 1.7, 95 percent CI: 1.3, 2.2). In this study population, physical injuries to other body parts, including the trunk, arms, or legs, were not related to ALS risk. These data support the notion that head injury may increase the risk of ALS.

Sports and trauma in amyotrophic lateral sclerosis revisited

An evidence-based review was undertaken of the literature published between 2002 and 2006 about sports, trauma and ALS in order to see if there were new data to modify the conclusions of a previous review (2003). The new data support the previous conclusions that physical activity and trauma are probably ("more likely than not") not risk factors for ALS (Level II conclusions). This review concludes also that the reports of an apparent excess of ALS in Italian soccer players likely reflect incorrect analysis of the data. The appearance of excess relies on accepting as valid estimation methods resulting in improbably low numbers of expected cases. A different method is proposed: it generates more plausible numbers of expected cases, compared to which there is no excess of total cases (Level C conclusion). A theoretical framework is developed to analyze the possible influence of a "healthy worker effect" on incidence of neurodegenerative diseases in cohorts of employed or formerly employed individuals. In lieu of theoretical speculations, data are needed to measure this effect, while controlling for known lifestyle factors and accounting for the effect of loss of competing causes of mortality.

Three soccer playing friends with simultaneous amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a neurodegenerative disease of largely unknown cause, predominantly affecting upper and lower motor neurons. A recent study in Italy suggested an increased incidence of ALS among professional Italian soccer players. We report a cluster of three amateur league soccer players who were friends from the same part of southern England, and developed ALS simultaneously. This might suggest that keen amateur soccer players are also at risk.

Sporadic amyotrophic lateral sclerosis as an infectious disease: A possible role of cyanobacteria?

The available epidemiological data for amyotrophic lateral sclerosis (ALS) support an infectious etiology and lead us to propose a new hypothesis. We examined older epidemiological data concerning categories of the population with increased incidence (aged people, people living in rural areas, farmers, breeders), more recent epidemiological reports regarding Italian soccer players, AIDS patients, people living in highly polluted areas, and reports of cases of conjugal and pregnancy-associated ALS. The toxic and infectious hypotheses lead us to suggest a role for cyanobacteria in the production of endogenous beta-N-methylamino-L-alanine. Infection from a cyanobacterium, or another ubiquitous bacterium having similar characteristics, may be the missing clue to the etiology of ALS. We speculate that ubiquitous bacteria secreting toxic amino acids and "colonizing" tissues and organs in the human body might be the common element linking motor neuron diseases in Guam to sporadic ALS in the rest of the world.

Amyotrophic lateral sclerosis mortality in the United States, 1979-2001

The etiology of nonfamilial amyotrophic lateral sclerosis (ALS) remains unknown. Earlier studies have suggested an increase in the incidence of ALS over time. We performed a retrospective analysis of ALS-associated death rates and trends in the United States for 1979-2001 using death records from the national multiple cause-of-death database. The US average annual age-adjusted ALS death rate was 1.84 per 100,000 persons for 1979 through 1998. Most deaths were among adults > or =65 years of age and the median age at death was 67 years. A small overall increase in the death rate was observed primarily between 1979 and 1983, with a subsequent plateau. This slight change in the overall rate reflected apparent increases in the rates among those persons > or =65 years of age, particularly women, and persons in the 20- to 49-year-old age group. The ALS-associated death rate appeared to differ by geographic area, with a higher occurrence among most northern states. Our findings suggest that the epidemiology of ALS-associated deaths in the United States demonstrated small increases in the overall age-adjusted death rate and in the death rates among elderly women and adults 20-49 years of age. Subpopulations at higher risk for ALS were males, whites, persons > or =65 years of age, and residents of northern states. This study provides information for further studies to examine the epidemiology and risk factors associated with ALS.

Amyotrophic lateral sclerosis: possible role of environmental influences

This treatise briefly discusses the genetic features of ALS and reviews environmental exposures in sporadic ALS. At least 10 genetic foci are responsible for cases of familial motor neuron disease and more are yet to be discovered. Research into sporadic ALS suggests that abundant factors apparently participate in the disease process. A singular cause and unifying disease and nerve dysfunction in polyneuropathies, a multitude of genetic, toxic, autoimmune, infectious, and systematic processes seem to be at play. The ALS syndrome likely will not be dissimilar.