Estimating the Occurrence of Amyotrophic Lateral Sclerosis among Gulf War (1990–1991) Veterans Using Capture-Recapture Methods

Adverse effect propensity: A new feature of Gulf War illness predicted by environmental exposures

A third of 1990-1 Gulf-deployed personnel developed drug/chemical-induced multisymptom illness, "Gulf War illness" (GWI). Veterans with GWI (VGWI) report increased drug/exposure adverse effects (AEs). Using previously collected data from a case-control study, we evaluated whether the fraction of exposures that engendered AEs ("AE Propensity") is increased in VGWI (it was); whether AE Propensity is related to self-rated "chemical sensitivity" (it did); and whether specific exposures "predicted" AE Propensity (they did). Pesticides and radiation exposure were significant predictors, with copper significantly "protective"-in the total sample (adjusted for GWI-status) and separately in VGWI and controls, on multivariable regression. Mitochondrial impairment and oxidative stress (OS) underlie AEs from many exposures irrespective of nominal specific mechanism. We hypothesize that mitochondrial toxicity and interrelated OS from pesticides and radiation position people on the steep part of the curve of mitochondrial impairment and OS versus symptom/biological disruption, amplifying impact of new exposures. Copper, meanwhile, is involved in critical OS detoxification processes.

Analysis of the spatial distribution of amyotrophic lateral sclerosis in Virginia

Objective: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that is usually fatal. Environmental exposures have been posited in the etiology of ALS, but few studies have modeled the spatial risk of ALS over large geographic areas. In this paper, our goal was to analyze the spatial distribution of ALS in Virginia and identify any areas with significantly elevated risk using Virginia ALS Association administrative data. Methods: We used Bayesian hierarchical spatial regression models to estimate the relative risk for ALS in Virginia census tracts, adjusting for several covariates posited to be associated with the disease. We used an intrinsic conditional autoregressive prior to allow for spatial correlation in the risk estimates and stabilize estimates over space. Results: Considerable variation in ALS risk existed across Virginia, with greater relative risk found in the central and western parts of the state. We identified significantly elevated relative risk in a number of census tracts. In particular, Henrico, Albemarle, and Botetourt counties all contained at least four census tracts with significantly elevated risk. Conclusions: We identified several areas with significantly elevated ALS risk across Virginia census tracts. These results can inform future studies of potential environmental triggers for the disease, whose etiology is still being understood.

Recent Advances in Extracellular Vesicles in Amyotrophic Lateral Sclerosis and Emergent Perspectives

Amyotrophic lateral sclerosis (ALS) is a severe and incurable neurodegenerative disease characterized by the progressive death of motor neurons, leading to paralysis and death. It is a rare disease characterized by high patient-to-patient heterogeneity, which makes its study arduous and complex. Extracellular vesicles (EVs) have emerged as important players in the development of ALS. Thus, ALS phenotype-expressing cells can spread their abnormal bioactive cargo through the secretion of EVs, even in distant tissues. Importantly, owing to their nature and composition, EVs' formation and cargo can be exploited for better comprehension of this elusive disease and identification of novel biomarkers, as well as for potential therapeutic applications, such as those based on stem cell-derived exosomes. This review highlights recent advances in the identification of the role of EVs in ALS etiopathology and how EVs can be promising new therapeutic strategies.

A likelihood ratio test for completed sampling in population size estimation studies

We propose a likelihood ratio test to assess that sampling has been completed in closed population size estimation studies. More precisely, we assess if the expected number of subjects that have never been sampled is below a user-specified threshold. The likelihood ratio test statistic has a nonstandard distribution under the null hypothesis. Critical values can be easily approximated and tabulated, and they do not depend on model specification. We illustrate in a simulation study and three real data examples, one of which involves ascertainment bias of amyotrophic lateral sclerosis in Gulf War veterans.

Long-term air pollution and risk of amyotrophic lateral sclerosis mortality in the Women's Health Initiative cohort

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with no cure. Although the etiology of sporadic ALS is largely unknown, environmental exposures may affect ALS risk.

OBJECTIVE

We investigated relationships between exposure to long-term ambient particulate matter (PM) and gaseous air pollution (AP) and ALS mortality.

METHODS

Within the Women's Health Initiative (WHI) cohort of 161,808 postmenopausal women aged 50-79 years at baseline (1993-1998), we performed a nested case-control study of 256 ALS deaths and 2486 matched controls with emphasis on PM constituents (PM_2.5, PM₁₀, and coarse PM [PM₁₀-_2.5]) and gaseous pollutants (NO_x, NO₂, SO₂, and ozone). Time-varying AP exposures estimates were averaged 5, 7.5, and 10 years prior to ALS death using both a GIS-based spatiotemporal generalized additive mixed model and ordinary kriging (empirical and multiple imputation, MI). Conditional logistic regression was used to estimate the relative risk of ALS death.

RESULTS

In general, PM_2.5 and PM₁₀-related risks were not significantly elevated using either method. However, for PM_10-2.5, odds ratios (ORs) were >1.0 for both methods at all time periods using MI and empirical data for PM_10-2.5 (coarse) except for 5 and 7.5 years using the kriging method with covariate adjustment.

CONCLUSION

This investigation adds to the body of information on long-term ambient AP exposure and ALS mortality. Specifically, the 2019 US Environmental Protection Agency (EPA) Integrated Science Assessment summarized the neurotoxic effects of PM_2.5, PM_10, and PM₁₀-_2.5. The conclusion was that evidence of an effect of coarse PM is suggestive but the data is presently not sufficient to infer a causal relationship. Further research on AP and ALS is warranted. As time from symptom onset to death in ALS is ∼2-4 years, earlier AP measures may also be of interest to ALS development. This is the first study of ALS and AP in postmenopausal women controlling for individual-level confounders.

A perspective on persistent toxicants in veterans and amyotrophic lateral sclerosis: identifying exposures determining higher ALS risk

Multiple studies indicate that United States veterans have an increased risk of developing amyotrophic lateral sclerosis (ALS) compared to civilians. However, the responsible etiological factors are unknown. In the general population, specific occupational (e.g. truck drivers, airline pilots) and environmental exposures (e.g. metals, pesticides) are associated with an increased ALS risk. As such, the increased prevalence of ALS in veterans strongly suggests that there are exposures experienced by military personnel that are disproportionate to civilians. During service, veterans may encounter numerous neurotoxic exposures (e.g. burn pits, engine exhaust, firing ranges). So far, however, there is a paucity of studies investigating environmental factors contributing to ALS in veterans and even fewer assessing their exposure using biomarkers. Herein, we discuss ALS pathogenesis in relation to a series of persistent neurotoxicants (often emitted as mixtures) including: chemical elements, nanoparticles and lipophilic toxicants such as dioxins, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. We propose these toxicants should be directly measured in veteran central nervous system tissue, where they may have accumulated for decades. Specific toxicants (or mixtures thereof) may accelerate ALS development following a multistep hypothesis or act synergistically with other service-linked exposures (e.g. head trauma/concussions). Such possibilities could explain the lower age of onset observed in veterans compared to civilians. Identifying high-risk exposures within vulnerable populations is key to understanding ALS etiopathogenesis and is urgently needed to act upon modifiable risk factors for military personnel who deserve enhanced protection during their years of service, not only for their short-term, but also long-term health.

Geographical clusters of amyotrophic lateral sclerosis and the Bradford Hill criteria

With the aim of shedding further light on the role of environmental factors in amyotrophic lateral sclerosis (ALS) etiology, we hereby conducted a historical narrative review to critically appraise the published reports on ALS geographical clusters using the modern interpretation of the Bradford Hill criteria for causation. Our research hypothesis was that the more criteria were met, the greater was the evidence supporting a causal association. We found that cluster studies that met the greatest number of Bradford's Hill criteria regarded the non-protein amino acid β-N-methylamino-L-alanine (L-BMAA) and exposure to metals and minerals, but the evidence for causation was at best moderate and was poor for other environmental factors. This defective picture might be attributed not only to the methodological approach adopted by published studies, but also to the inherent difficulties in the application of Bradford Hill criteria, due to the complexity of the disease phenotype and the underlying pathogenic mechanisms.

Military service and related risk factors for amyotrophic lateral sclerosis

BACKGROUND

The cause of amyotrophic lateral sclerosis (ALS) is unknown, but occupations have been explored as a potential proxy measure of risk. There is a substantial body of literature connecting military service to ALS. We aimed to summarize and assess the quality of this evidence.

METHODS

Systematic review of the literature, including observational studies which explored one of the following exposures: general military service (army, air force, marines, or navy); or specific exposures associated with military service measured among military personnel. The outcome of interest was ALS incidence, which could include onset, diagnosis, or death from ALS.

RESULTS

A total of 2642 articles were screened. Following exclusion, 19 articles remained for inclusion in the systematic review, including 1 meta-analysis and 18 original observational studies. Most studies were of moderate quality. In general, the relationship between military service was suggestive of an increased risk, particularly among Gulf War and WWII veterans. Exposure to pesticides (including Agent Orange) certain chemicals (exhaust, burning agents), heavy metals, and head trauma appeared to increase the risk of ALS among military personnel.

CONCLUSIONS

There is a possible association between military service and the subsequent development of ALS; however, the evidence was limited. Studies were generally hindered by small sample sizes and inadequate follow-up time. Future studies should endeavor to objectively measure specific exposures, or combinations thereof, associated with military service, as this will be of vital importance in implementing preventative strategies into military organizations.

Exploring the Role of Chemokine Receptor 6 (Ccr6) in the BXD Mouse Model of Gulf War Illness

Gulf War illness (GWI) is a chronic and multi-symptomatic disorder with persistent neuroimmune symptomatology. Chemokine receptor 6 (CCR6) has been shown to be involved in several inflammation disorders in humans. However, the causative relationship between CCR6 and neuroinflammation in GWI has not yet been investigated. By using RNA-seq data of prefrontal cortex (PFC) from 31 C57BL/6J X DBA/2J (BXD) recombinant inbred (RI) mouse strains and their parental strains under three chemical treatment groups – saline control (CTL), diisopropylfluorophosphate (DFP), and corticosterone combined with diisopropylfluorophosphate (CORT+DFP), we identified Ccr6 as a candidate gene underlying individual differences in susceptibility to GWI. The Ccr6 gene is cis-regulated and its expression is significantly correlated with CORT+DFP treatment. Its mean transcript abundance in PFC of BXD mice decreased 1.6-fold (p < 0.0001) in the CORT+DFP group. The response of Ccr6 to CORT+DFP is also significantly different (p < 0.0001) between the parental strains, suggesting Ccr6 is affected by both host genetic background and chemical treatments. Pearson product-moment correlation analysis revealed 1473 Ccr6-correlated genes (p < 0.05). Enrichment of these genes was seen in the immune, inflammation, cytokine, and neurological related categories. In addition, we also found five central nervous system-related phenotypes and fecal corticosterone concentration have significant correlation (p < 0.05) with expression of Ccr6 in the PFC. We further established a protein-protein interaction subnetwork for the Ccr6-correlated genes, which provides an insight on the interaction of G protein-coupled receptors, kallikrein-kinin system and neuroactive ligand-receptors. This analysis likely defines the heterogeneity and complexity of GWI. Therefore, our results suggest that Ccr6 is one of promising GWI biomarkers.

Treatment for Gulf War Illness (GWI) with KPAX002 (methylphenidate hydrochloride + GWI nutrient formula) in subjects meeting the Kansas case definition: A prospective, open-label trial

This study tested the safety, tolerability, and efficacy of KPAX002-a combination of methylphenidate hydrochloride plus a micronutrient formula designed to support mitochondrial function-as a treatment for Gulf War Illness (GWI). This open-label trial enrolled 17 subjects meeting the Kansas case definition for GWI. Of the 17 subjects enrolled, 15 qualified for the Intent-to-Treat (ITT) population with 10 subjects completing the trial per protocol. All analyses were on the ITT population. At 12 weeks, subjects taking KPAX002 experienced a mean 25% reduction in their overall GWI symptoms severity as measured by the GWI Symptoms Assessment Tool (SAT) (p < 0.001). Visual analog scale scores were also significantly reduced for fatigue (p = 0.019), cognitive symptoms (p = 0.006), sleep problems (p = 0.026), and pain (p = 0.05). Twelve weeks of KPAX002 administration resulted in a significant improvement in GWI symptoms with an acceptable side effect profile. A larger randomized, double-blinded, placebo-controlled trial is necessary to determine if the observed benefit can be replicated.

Traumatic injury induces stress granule formation and enhances motor dysfunctions in ALS/FTD models

Traumatic brain injury (TBI) has been predicted to be a predisposing factor for amyotrophic lateral sclerosis (ALS) and other neurological disorders. Despite the importance of TBI in ALS progression, the underlying cellular and molecular mechanisms are still an enigma. Here, we examined the contribution of TBI as an extrinsic factor and investigated whether TBI influences the susceptibility of developing neurodegenerative symptoms. To evaluate the effects of TBI in vivo, we applied mild to severe trauma to Drosophila and found that TBI leads to the induction of stress granules (SGs) in the brain. The degree of SGs induction directly correlates with the level of trauma. Furthermore, we observed that the level of mortality is directly proportional to the number of traumatic hits. Interestingly, trauma-induced SGs are ubiquitin, p62 and TDP-43 positive, and persistently remain over time suggesting that SGs might be aggregates and exert toxicity in our fly models. Intriguingly, TBI on animals expressing ALS-linked genes increased mortality and locomotion dysfunction suggesting that mild trauma might aggravate neurodegenerative symptoms associated with ALS. Furthermore, we found elevated levels of high molecular weight ubiquitinated proteins and p62 in animals expressing ALS-causing genes with TBI, suggesting that TBI may lead to the defects in protein degradation pathways. Finally, we observed that genetic and pharmacological induction of autophagy enhanced the clearance of SGs and promoted survival of flies in vivo. Together, our study demonstrates that trauma can induce SG formation in vivo and might enhance neurodegenerative phenotypes in the fly models of ALS.

Military service, deployments, and exposures in relation to amyotrophic lateral sclerosis survival

BACKGROUND

Military veterans may have higher rates of amyotrophic lateral sclerosis (ALS) mortality than non-veterans. Few studies, with sparse exposure information and mixed results, have studied relationships between military-related factors and ALS survival. We evaluated associations between military-related factors and ALS survival among U.S. military veteran cases.

METHODS

We followed 616 medical record-confirmed cases from enrollment (2005-2010) in the Genes and Environmental Exposures in Veterans with Amyotrophic Lateral Sclerosis study until death or July 25, 2013, whichever came first. We ascertained vital status information from several sources within the Department of Veterans Affairs. We obtained information regarding military service, deployments, and 39 related exposures via standardized telephone interviews. We used Cox proportional hazards regression models to estimate hazard ratios (HRs) and 95% confidence intervals. We adjusted for potential confounding and missing covariate data biases via inverse probability weights. We also used inverse probability weights to adjust for potential selection bias among a case group that included a disproportionate number of long-term survivors at enrollment.

RESULTS

We observed 446 deaths during 24,267 person-months of follow-up (median follow-up: 28 months). Survival was shorter for cases who served before 1950, were deployed to World War II, or mixed and applied burning agents, with HRs between 1.58 and 2.57. Longer survival was associated with exposure to: paint, solvents, or petrochemical substances; local food not provided by the Armed Forces; or burning agents or Agent Orange in the field with HRs between 0.56 and 0.73.

CONCLUSIONS

Although most military-related factors were not associated with survival, associations we observed with shorter survival are potentially important because of the large number of military veterans.

On the design of closed recapture experiments

We propose a method to plan the number of occasions of recapture experiments for population size estimation. We do so by fixing the smallest number of capture occasions so that the expected length of the profile confidence interval is less than or equal to a fixed threshold. In some cases, we solve the optimization problem in closed form. For more complex models we use numerical optimization. We detail models assuming homogeneous, time-varying, subject-specific capture probabilities, behavioral response to capture, and combining behavioral response with subject-specific effects. The principle we propose can be extended to plan any other model specification. We formally show the validity of the approach by proving distributional convergence. We illustrate with simulations and challenging examples in epidemiology and ecology. We report that in many cases adding as few as two sampling occasions may substantially reduce the length of confidence intervals.

Preliminary Results of National Amyotrophic Lateral Sclerosis (ALS) Registry Risk Factor Survey Data

BACKGROUND

The National ALS Registry is made up of two components to capture amyotrophic lateral sclerosis (ALS) cases: national administrative databases (Medicare, Medicaid, Veterans Health Administration and Veterans Benefits Administration) and self-identified cases captured by the Registry's web portal. This study describes self-reported characteristics of U.S. adults with ALS using the data collected by the National ALS Registry web portal risk factor surveys only from October 19, 2010 through December 31, 2013.

OBJECTIVE

To describe findings from the National ALS Registry's web portal risk factor surveys.

MEASUREMENTS

The prevalence of select risk factors among adults with ALS was determined by calculating the frequencies of select risk factors-smoking and alcohol (non, current and former) histories, military service and occupational history, and family history of neurodegenerative diseases such as ALS, Alzheimer's and/or Parkinson's.

RESULTS

Nearly half of survey respondents were ever smokers compared with nearly 41% of adults nationally. Most respondents were ever drinkers which is comparable to national estimates. The majority were light drinkers. Nearly one-quarter of survey respondents were veterans compared with roughly 9% of US adults nationally. Most respondents were retired or disabled. The industries in which respondents were employed for the longest time were Professional and Scientific and Technical Services. When family history of neurodegenerative diseases in first degree relatives was evaluated against our comparison group, the rates of ALS were similar, but were higher for Parkinson's disease, Alzheimer's disease and any neurodegenerative diseases.

CONCLUSIONS

The National ALS Registry web portal, to our knowledge, is the largest, most geographically diverse collection of risk factor data about adults living with ALS. Various characteristics were consistent with other published studies on ALS risk factors and will allow researchers to generate hypotheses for future research.

Military Service and Amyotrophic Lateral Sclerosis in a Population-based Cohort

BACKGROUND

Military service has been suggested to be associated with an increased risk of amyotrophic lateral sclerosis (ALS), but only one prospective study-of a volunteer cohort-has examined this question.

METHODS

We prospectively assessed the relation between service in the military and ALS mortality among participants in the National Longitudinal Mortality Study, a population-representative cohort of U.S. men and women surveyed from 1973 through 2002. Participant follow-up was conducted from 1979 through 2002 for ALS mortality. There were 696,743 men and 392,571 women who were 25 years old or more with military service data. In this group, there were 375 male ALS deaths and 96 female ALS deaths. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards.

RESULTS

Men who served in the military had an increased adjusted ALS death rate [HR: 1.23; 95% confidence interval (CI): 0.98, 1.53] compared with those who did not serve. An increase in ALS mortality was found among those who served during World War II (HR: 1.47; 95% CI: 1.13, 1.91) but not during other time periods. This pattern of results was similar for women, but with larger confidence intervals (HR for military service: 1.26; 95% CI: 0.29, 5.59; HR for service during World War II: 2.03; 95% CI: 0.45, 9.05).

CONCLUSIONS

Military personnel have an increased risk of ALS, which may be specific to certain service periods although there was no data on actual deployment. Because of the longer follow-up time for World War II veterans, we cannot rule out that increased risk for those who served during other periods would be seen with further follow-up.

Recent research on Gulf War illness and other health problems in veterans of the 1991 Gulf War: Effects of toxicant exposures during deployment

Veterans of Operation Desert Storm/Desert Shield - the 1991 Gulf War (GW) - are a unique population who returned from theater with multiple health complaints and disorders. Studies in the U.S. and elsewhere have consistently concluded that approximately 25-32% of this population suffers from a disorder characterized by symptoms that vary somewhat among individuals and include fatigue, headaches, cognitive dysfunction, musculoskeletal pain, and respiratory, gastrointestinal and dermatologic complaints. Gulf War illness (GWI) is the term used to describe this disorder. In addition, brain cancer occurs at increased rates in subgroups of GW veterans, as do neuropsychological and brain imaging abnormalities. Chemical exposures have become the focus of etiologic GWI research because nervous system symptoms are prominent and many neurotoxicants were present in theater, including organophosphates (OPs), carbamates, and other pesticides; sarin/cyclosarin nerve agents, and pyridostigmine bromide (PB) medications used as prophylaxis against chemical warfare attacks. Psychiatric etiologies have been ruled out. This paper reviews the recent literature on the health of 1991 GW veterans, focusing particularly on the central nervous system and on effects of toxicant exposures. In addition, it emphasizes research published since 2008, following on an exhaustive review that was published in that year that summarizes the prior literature (RACGWI, 2008). We conclude that exposure to pesticides and/or to PB are causally associated with GWI and the neurological dysfunction in GW veterans. Exposure to sarin and cyclosarin and to oil well fire emissions are also associated with neurologically based health effects, though their contribution to development of the disorder known as GWI is less clear. Gene-environment interactions are likely to have contributed to development of GWI in deployed veterans. The health consequences of chemical exposures in the GW and other conflicts have been called "toxic wounds" by veterans. This type of injury requires further study and concentrated treatment research efforts that may also benefit other occupational groups with similar exposure-related illnesses.

Chronic traumatic encephalopathy: contributions from the Boston University Center for the Study of Traumatic Encephalopathy

OBJECTIVE

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease associated with repetitive brain trauma (RBT). Initially described in boxers, CTE has now been found in other contact sport athletes with a history of RBT. In recent years, there has been tremendous media attention regarding CTE, primarily because of the deaths of high profile American football players who were found to have CTE upon neuropathological examination. However, the study of CTE remains in its infancy. This review focuses on research from the Centre for the Study of Traumatic Encephalopathy (CSTE) at Boston University.

METHODS

This study reviews the formation of the CSTE, major CSTE publications and current ongoing research projects at the CSTE.

RESULTS

The neuropathology of CTE has been well-described. Current research focuses on: methods of diagnosing the disease during life (including the development of biomarkers), examination of CTE risk factors (including genetic susceptibility and head impact exposure variables); description of the clinical presentation of CTE; development of research diagnostic criteria for Traumatic Encephalopathy Syndrome; and assessment of mechanism and pathogenesis.

CONCLUSIONS

Current research at the BU CSTE is aimed at increasing understanding of the long-term consequences of repetitive head impacts and attempting to begin to answer several of the unanswered questions regarding CTE.

Comparing capture-recapture methods for estimation of the size of small and medium-sized populations using empirical data on commercial turkey farms in Canada

The study objectives were (1) to conduct a systematic review of the performance of capture-recapture methods; (2) to use empirical data to estimate population size in a small-sized population (turkey breeder farms) and a medium-sized population (meat turkey farms) by applying two-source capture-recapture methods (the Lincoln-Petersen, the Chapman, and Chao's lower-bound estimators) and multi-source capture-recapture methods (the log-linear modeling and sample coverage approaches); and (3) to compare the performance of these methods in predicting the true population sizes (2007 data). Our set-up was unique in that we knew the population sizes for turkey breeder farms (99) and meat turkey farms (592) in Canada in 2007, which we applied as our true population sizes, and had surveillance data from the Canadian Notifiable Avian Influenza Surveillance System (2008-2012). We defined each calendar year of sampling as a data source. We confirmed that the two-source capture-recapture methods were sensitive to the violation of the local independence assumption. The log-linear modeling and sample coverage approaches yielded estimates that were closer to the true population sizes than were the estimates provided by the two-source methods for both populations. The performance of both multi-source capture-recapture methods depended on the number of data sources analyzed and the size of the population. Simulation studies are recommended to better understand the limits of each multi-source capture-recapture method.

Detection of cyanotoxins, β-N-methylamino-L-alanine and microcystins, from a lake surrounded by cases of amyotrophic lateral sclerosis

A cluster of amyotrophic lateral sclerosis (ALS) has been previously described to border Lake Mascoma in Enfield, NH, with an incidence of ALS approximating 25 times expected. We hypothesize a possible association with cyanobacterial blooms that can produce β-N-methylamino-L-alanine (BMAA), a neurotoxic amino acid implicated as a possible cause of ALS/PDC in Guam. Muscle, liver, and brain tissue samples from a Lake Mascoma carp, as well as filtered aerosol samples, were analyzed for microcystins (MC), free and protein-bound BMAA, and the BMAA isomers 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl)glycine (AEG). In carp brain, BMAA and DAB concentrations were 0.043 μg/g ± 0.02 SD and 0.01 μg/g ± 0.002 SD respectively. In carp liver and muscle, the BMAA concentrations were 1.28 μg/g and 1.27 μg/g respectively, and DAB was not detected. BMAA was detected in the air filters, as were the isomers DAB and AEG. These results demonstrate that a putative cause for ALS, BMAA, exists in an environment that has a documented cluster of ALS. Although cause and effect have not been demonstrated, our observations and measurements strengthen the association.

Epidemiology of amyotrophic lateral sclerosis and effect of riluzole on disease course

OBJECTIVES

To assess the epidemiology of ALS in Austria and to evaluate the long-term effect of riluzole treatment on survival.

METHODS

Hospital discharge and riluzole prescription databases were used to identify ALS cases from January 2008 to June 2012. Using the capture-recapture method we evaluated the incidence and prevalence of ALS and patients' survival in dependence of age, gender and riluzole treatment.

RESULTS

The corrected incidence and prevalence of ALS were 3.13/100,000 person-years (95% CI, 2.77 to 3.50) and 9.14/100,000 persons (95% CI, 8.53 to 9.79), respectively. Median survival from diagnosis was 676 days (95% CI, 591 to 761). A younger age at diagnosis was associated with a longer survival. Gender did not appear to affect survival time. Riluzole therapy was associated with a survival advantage only for the initial treatment period. The adjusted hazard ratio of mortality for using riluzole increased continually over time resulting in an apparent reversal of its beneficial effect after 6 months of therapy.

CONCLUSIONS

We report incidence and prevalence estimates that are on the upper end of the wide range discussed in literature. Riluzole seems to exert a beneficial effect only in the first 6 months of therapy.

Military service, deployments, and exposures in relation to amyotrophic lateral sclerosis etiology and survival

Rates of amyotrophic lateral sclerosis (ALS) have been reported to be higher among US military veterans, who currently number more than 21 million, but the causal factor(s) has not been identified. We conducted a review to examine the weight of evidence for associations between military service, deployments, and exposures and ALS etiology and survival. Thirty articles or abstracts published through 2013 were reviewed. Although the current evidence suggests a positive association with ALS etiology, it is too limited to draw firm conclusions regarding associations between military service and ALS etiology or survival. Some evidence suggests that deployment to the 1990-1991 Persian Gulf War may be associated with ALS etiology, but there is currently no strong evidence that any particular military exposure is associated with ALS etiology. Future studies should address the limitations of previous ones, such as reliance on mortality as a surrogate for incidence, a dearth of survival analyses, lack of clinical data, low statistical power, and limited exposure assessment. The Genes and Environmental Exposures in Veterans with Amyotrophic Lateral Sclerosis (GENEVA) Study is one such study, but additional research is needed to determine whether military-related factors are associated with ALS and to assess potential prevention strategies.

Mitochondrial dysfunction in Gulf War illness revealed by 31Phosphorus Magnetic Resonance Spectroscopy: a case-control study

BACKGROUND

Approximately 1/3 of 1990-1 Gulf War veterans developed chronic multisymptom health problems. Implicated exposures bear mechanisms that adversely affect mitochondria. Symptoms emphasize fatigue, cognition and muscle (brain and muscle are aerobically demanding); with protean additional domains affected, compatible with mitochondrial impairment. Recent evidence supports treatments targeting cell bioenergetics (coenzyme10) to benefit Gulf War illness symptoms. However, no evidence has directly documented mitochondrial or bioenergetic impairment in Gulf War illness.

OBJECTIVE

We sought to objectively assess for mitochondrial dysfunction, examining post-exercise phosphocreatine-recovery time constant (PCr-R) using (31)Phosphorus Magnetic Resonance Spectroscopy ((31)P-MRS), in Gulf War veterans with Gulf War illness compared to matched healthy controls. PCr-R has been described as a "robust and practical" index of mitochondrial status.

DESIGN AND PARTICIPANTS

Case-control study from 2012-2013. Fourteen community-dwelling Gulf War veterans and matched controls from the San Diego area comprised 7 men meeting CDC and Kansas criteria for Gulf War illness, and 7 non-deployed healthy controls matched 1:1 to cases on age, sex, and ethnicity.

OUTCOME MEASURE

Calf muscle phosphocreatine was evaluated by (31)P-MRS at rest, through 5 minutes of foot pedal depression exercise, and in recovery, to assess PCr-R. Paired t-tests compared cases to matched controls.

RESULTS

PCr-R was significantly prolonged in Gulf War illness cases vs their matched controls: control values, mean ± SD, 29.0 ± 8.7 seconds; case values 46.1 ± 18.0 seconds; difference 17.1 ± 14.9 seconds; p = 0.023. PCr-R was longer for cases relative to their matched controls for all but one pair; moreover while values clustered under 31 seconds for all but one control, they exceeded 35 seconds (with a spread up to 70 seconds) for all but one case.

DISCUSSION

These data provide the first direct evidence supporting mitochondrial dysfunction in Gulf War illness. Findings merit replication in a larger study and/or corroboration with additional mitochondrial assessment tools.

Clinical perspective on oxidative stress in sporadic amyotrophic lateral sclerosis

Sporadic amyotrophic lateral sclerosis (ALS) is one of the most devastating neurological diseases; most patients die within 3 to 4 years after symptom onset. Oxidative stress is a disturbance in the pro-oxidative/antioxidative balance favoring the pro-oxidative state. Autopsy and laboratory studies in ALS indicate that oxidative stress plays a major role in motor neuron degeneration and astrocyte dysfunction. Oxidative stress biomarkers in cerebrospinal fluid, plasma, and urine are elevated, suggesting that abnormal oxidative stress is generated outside of the central nervous system. Our review indicates that agricultural chemicals, heavy metals, military service, professional sports, excessive physical exertion, chronic head trauma, and certain foods might be modestly associated with ALS risk, with a stronger association between risk and smoking. At the cellular level, these factors are all involved in generating oxidative stress. Experimental studies indicate that a combination of insults that induce modest oxidative stress can exert additive deleterious effects on motor neurons, suggesting that multiple exposures in real-world environments are important. As the disease progresses, nutritional deficiency, cachexia, psychological stress, and impending respiratory failure may further increase oxidative stress. Moreover, accumulating evidence suggests that ALS is possibly a systemic disease. Laboratory, pathologic, and epidemiologic evidence clearly supports the hypothesis that oxidative stress is central in the pathogenic process, particularly in genetically susceptive individuals. If we are to improve ALS treatment, well-designed biochemical and genetic epidemiological studies, combined with a multidisciplinary research approach, are needed and will provide knowledge crucial to our understanding of ALS etiology, pathophysiology, and prognosis.

The epidemiology of ALS: a conspiracy of genes, environment and time

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive neurodegenerative disease of motor neurons, resulting in worsening weakness of voluntary muscles until death from respiratory failure occurs after about 3 years. Although great advances have been made in our understanding of the genetic causes of ALS, the contribution of environmental factors has been more difficult to assess. Large-scale studies of the clinical patterns of ALS, individual histories preceding the onset of ALS, and the rates of ALS in different populations and groups have led to improved patient care, but have not yet revealed a replicable, definitive environmental risk factor. In this Review, we outline what is currently known of the environmental and genetic epidemiology of ALS, describe the current state of the art with respect to the different types of ALS, and explore whether ALS should be considered a single disease or a syndrome. We examine the relationship between genetic and environmental risk factors, and propose a disease model in which ALS is considered to be the result of environmental risks and time acting on a pre-existing genetic load, followed by an automatic, self-perpetuating decline to death.

Spatial analysis of amyotrophic lateral sclerosis in Northern New England, USA, 1997-2009

INTRODUCTION

An environmental trigger of sporadic amyotrophic lateral sclerosis (ALS) is supported by geographic disparities in ALS incidence and development of the disease in conjugal couples. This study aims to investigate the incidence of ALS in the Northern New England states of New Hampshire (NH), Vermont (VT), and Maine (ME).

METHODS

We reviewed medical records and community databases to identify dwelling addresses of 688 patients diagnosed with ALS in 1997-2009 in NH, VT, and ME. We used spatial analysis to identify clusters of census block groups with statistically significant high incidence.

RESULTS

We identified 11 clusters of statistically significant high incidence, each containing 6 or more cases of ALS. These 11 clusters are grouped in 4 distinct regions.

CONCLUSIONS

There appear to be areas of significant spatial clustering within Northern New England. Further analysis will be needed to confirm whether there is any correlation between these areas and potential environmental risk factors.

Utility of capture-recapture methodology to assess completeness of amyotrophic lateral sclerosis case ascertainment

BACKGROUND

With the establishment of a national amyotrophic lateral sclerosis (ALS) registry in the United States, methods are needed to ascertain the completeness of case ascertainment, especially in view of the proposal to rely largely on existing data sources.

METHODS

Data about ALS patients residing in the 5-county metropolitan Atlanta area (within the State of Georgia) from 2001 to 2005 were categorized according to their source--ALS Association, clinical (Emory Healthcare, community neurologist, Veterans Health Administration, Veterans Benefits Administration), Medicare and death certificates. ALS diagnoses were verified using chart review. Capture-recapture analyses were carried out using log-linear modeling, stratified by age and race.

RESULTS

The final model (based on 798 cases), which included the 4 main sources and 3 two-way interaction terms, yielded an estimated total population of 880 (95% CI 816-965), indicating that the combination of case-finding methods identified about 90.7% of cases. The estimated 5-year period prevalence is 38.5/100,000 (95% CI 35.66-42.19).

CONCLUSION

This study highlights gaps in data based on existing data sources and illustrates a method for combining data from multiple sources to help facilitate the successful establishment of a US national ALS registry.

Spatial clustering of amyotrophic lateral sclerosis and the potential role of BMAA

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative syndrome which has no known cause, except for a small proportion of cases which are genetically inherited. The development of ALS likely involves both genetic and environmental risk factors. Environmental risk factors implicated in ALS have included heavy metals, trauma, pesticides, electrical injuries, electromagnetic radiation and the cyanobacterial-derived neurotoxin beta-N-methylamino-L-alanine (BMAA). To investigate possible environmental risks, a number of epidemiological studies of ALS have been conducted. Some of these studies employ spatial analysis techniques that examine for spatial clusters of ALS and can help guide further research into identifying environmental exposures. Despite identifying geographical disparities in the distribution of ALS cases, these studies have not provided any clear associations with environmental factors. We review the literature on important studies of spatial clustering of ALS and explore the hypothesized link between the neurotoxin BMAA and ALS.

The epidemiology and treatment of ALS: focus on the heterogeneity of the disease and critical appraisal of therapeutic trials

Abstract Effective treatments for amyotrophic lateral sclerosis (ALS) have remained elusive. Only riluzole, a drug thought to affect glutamate metabolism, improves survival albeit to modest extent. Explanations for the negative results of therapeutic trials include a likely heterogeneity, both in disease susceptibility and pathogenic mechanisms, and faulty methodology of clinical trials. Further understanding of these factors will lead to improvements in patient stratification, and in the design of future clinical trials.

TDP-43 proteinopathy and motor neuron disease in chronic traumatic encephalopathy

Epidemiological evidence suggests that the incidence of amyotrophic lateral sclerosis is increased in association with head injury. Repetitive head injury is also associated with the development of chronic traumatic encephalopathy (CTE), a tauopathy characterized by neurofibrillary tangles throughout the brain in the relative absence of β-amyloid deposits. We examined 12 cases of CTE and, in 10, found a widespread TAR DNA-binding protein of approximately 43kd (TDP-43) proteinopathy affecting the frontal and temporal cortices, medial temporal lobe, basal ganglia, diencephalon, and brainstem. Three athletes with CTE also developed a progressive motor neuron disease with profound weakness, atrophy, spasticity, and fasciculations several years before death. In these 3 cases, there were abundant TDP-43-positive inclusions and neurites in the spinal cord in addition to tau neurofibrillary changes, motor neuron loss, and corticospinal tract degeneration. The TDP-43 proteinopathy associated with CTE is similar to that found in frontotemporal lobar degeneration with TDP-43 inclusions, in that widespread regions of the brain are affected. Akin to frontotemporal lobar degeneration with TDP-43 inclusions, in some individuals with CTE, the TDP-43 proteinopathy extends to involve the spinal cord and is associated with motor neuron disease. This is the first pathological evidence that repetitive head trauma experienced in collision sports might be associated with the development of a motor neuron disease.

Association between blood lead and the risk of amyotrophic lateral sclerosis

The authors conducted a 2003-2007 case-control study including 184 cases and 194 controls to examine the association between blood lead and the risk of amyotrophic lateral sclerosis (ALS) among US veterans and to explore the influence on this association of bone turnover and genetic factors related to lead toxicokinetics. Blood lead, plasma biomarkers of bone formation (procollagen type 1 amino-terminal peptide (PINP)) and resorption (C-terminal telopeptides of type 1 collagen (CTX)), and the K59N polymorphism in the delta-aminolevulinic acid dehydratase gene, ALAD, were measured. Odds ratios and 95% confidence intervals for the association of blood lead with ALS were estimated with unconditional logistic regression after adjustment for age and bone turnover. Blood lead levels were higher among cases compared with controls (P < 0.0001, age adjusted). A doubling of blood lead was associated with a 1.9-fold increased risk of ALS (95% confidence interval: 1.3, 2.7) after adjustment for age and CTX. Additional adjustment for PINP did not alter the results. Significant lead-ALS associations were observed in substrata of PINP and CTX levels. The K59N polymorphism in the ALAD gene did not modify the lead-ALS association (P = 0.32). These results extend earlier findings by accounting for bone turnover in confirming the association between elevated blood lead level and higher risk of ALS.

Cyanobacteria and BMAA exposure from desert dust: a possible link to sporadic ALS among Gulf War veterans

Veterans of the 1990-1991 Gulf War have been reported to have an increased incidence of amyotrophic lateral sclerosis (ALS) compared to personnel who were not deployed. An excess of ALS cases was diagnosed in Gulf War veterans younger than 45 years of age. Increased ALS among Gulf War veterans appears to be an outbreak time-limited to the decade following the Gulf War. Seeking to identify biologically plausible environmental exposures, we have focused on inhalation of cyanobacteria and cyanotoxins carried by dust in the Gulf region, particularly Qatar. Cyanobacterial crusts and mats are widespread in the deserts of Qatar, occupying up to 56% of the available area in some microhabitats. These cyanobacterial crusts, which help bind the desert sands, are dormant throughout most of the year, but during brief spring rains actively photosynthesize. When disturbed by vehicular traffic or other military activities, the dried crusts and mats can produce significant dust. Using HPLC/FD, an amino acid analyzer, UPLC/MS, and triple quadrupole LC/MS/MS we find that the dried crusts and mats contain neurotoxic cyanobacterial toxins, including beta-N-methylamino-L-alanine (BMAA) and 2,4 diaminobutyric acid (DAB). If dust containing cyanobacteria is inhaled, significant exposure to BMAA and other cyanotoxins may occur. We suggest that inhalation of BMAA, DAB, and other aerosolized cyanotoxins may constitute a significant risk factor for the development of ALS and other neurodegenerative diseases.

[Retrospective study of ALS in French military personnel]

INTRODUCTION

An apparent increased risk for developing Amyotrophic Lateral Sclerosis (ALS), a multifactorial neurodegenerative disease, is considered to exist in the military population.

PATIENTS AND METHODS

ALS military and veteran patients were retrospectively recruited in April 2008 by searching medical data (Hippocrate) and repayment data (Erasme) of the French National Military Health Care Fund (Caisse nationale militaire de sécurité sociale, CNMSS) from de January 1991 to December 2007.

RESULTS

We report a series of 73 patients, 69 male and four female, average age of 52.5 years (range 27 to 72 years) with a peak of patients in the 50-59 year age class. The branch of military service was Army (n=26 patients), Air force (n=14), Navy (n=10) and State Police Force (n=22). The incidence among male active duty military personnel was stable from 2002 to 2007; it was less than the general population (1.7/100,000 per year in 2007), but higher in the 40-44 and 50-54 year age classes (1.90 and 5.07/100,000 per year in 2007 respectively). Duration of active duty was on average 31 years.

CONCLUSION

The retrospective nature of the data and the incomplete population with loss of retired military personnel without CNMSS affiliation are limitations of our study. Another means of collecting all cases of ALS among French military personnel and veterans would be to conduct a search in the 17 ALS centers in France with analysis by occupational activity for entire career.

Spatial analysis of the etiology of amyotrophic lateral sclerosis among 1991 Gulf War veterans

BACKGROUND

Veterans of the 1991 Gulf War have an increased risk of amyotrophic lateral sclerosis (ALS), but the etiology is unknown.

OBJECTIVES

This study sought to identify geographic areas with elevated risk for the later development of ALS among military personnel who served in the first Gulf War.

METHODS

A unified geographic information system (GIS) was constructed to allow analysis of secondary data on troop movements in the 1991 Gulf War theatre in the Persian Gulf region including Iraq, northern Saudi Arabia, and Kuwait. We fit Bayesian Poisson regression models to adjust for potential risk factors, including one relatively discrete environmental exposure, and to identify areas associated with elevated risk of ALS.

RESULTS

We found that service in particular locations of the Gulf was associated with an elevated risk for later developing ALS, both before and after adjustment for branch of service and potential of exposure to chemical warfare agents in and around Khamisiyah, Iraq.

CONCLUSIONS

Specific geographic locations of troop units within the 1991 Gulf War theatre are associated with an increased risk for the subsequent development of ALS among members of those units. The identified spatial locations represent the logical starting points in the search for potential etiologic factors of ALS among Gulf War veterans. Of note, for locations where the relative odds of subsequently developing ALS are among the highest, specific risk factors, whether environmental or occupationally related, have not been identified. The results of spatial models can be used to subsequently look for risk factors that follow the spatial pattern of elevated risk.

Genes and Environmental Exposures in Veterans with Amyotrophic Lateral Sclerosis: the GENEVA study. Rationale, study design and demographic characteristics

Recent reports of a potentially increased risk of amyotrophic lateral sclerosis (ALS) for veterans deployed to the 1990-1991 Persian Gulf War prompted the Department of Veterans Affairs to establish a National Registry of Veterans with ALS, charged with the goal of enrolling all US veterans with a neurologist-confirmed diagnosis of ALS. The Genes and Environmental Exposures in Veterans with ALS study (GENEVA) is a case-control study presently enrolling cases from the Department of Veterans Affairs registry and a representative sample of veteran controls to evaluate the joint contributions of genetic susceptibility and environmental exposures to the risk of sporadic ALS. The GENEVA study design, recruitment strategies, methods of collecting DNA samples and environmental risk factor information are described here, along with a summary of demographic characteristics of the participants (537 cases, 292 controls) enrolled to date.

The impact of the 1991 Gulf War on the mind and brain: findings from neuropsychological and neuroimaging research

Many veterans of the 1991 Gulf War (GW) have complained of somatic and cognitive symptoms that may be neurological in nature. However, whether or not changes in brain function are associated with GW service continues to be debated. Studies of GW veterans using objective, performance-based neuropsychological measures have yielded inconsistent findings, with those indicating deficits among GW veterans typically revealing only relatively mild levels of neuropsychological impairment. Further, performances on objective neuropsychological tasks show little correspondence to subjective perceptions of cognitive functioning. Although preliminary magnetic resonance spectroscopy (MRS) studies demonstrate reduced N-acetylaspartate-to-creatine (NAA/Cr) ratio in select brain regions among GW veterans who report health concerns, this work requires further replication with larger, more representative samples. There is no evidence from neuroimaging studies of a non-specific effect of GW service or of changes in brain structure or function related to health status when conventional radiological methods are used. Owing to the paucity of objective exposure, baseline health data, and the now significant time elapsed since the GW, aetiological issues may never be fully resolved. Therefore, research addressing clinical management of GW veterans with neuropsychological dysfunction and neuroimaging abnormalities may prove more fruitful than exclusive focus on aetiology.

Early abnormalities in transgenic mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative and fatal human disorder characterized by progressive loss of motor neurons. Transgenic mouse models of ALS are very useful to study the initial mechanisms underlying this neurodegenerative disease. We will focus here on the earlier abnormalities observed in superoxide dismutase 1 (SOD1) mutant mice. Several hypotheses have been advanced to explain the selective loss of motor neurons such as apoptosis, neurofilament disorganisation, oxidative stress, mitochondrial dysfunction, astrogliosis and excitotoxicity. Although disease onset appears at adulthood, recent studies have detected abnormalities during embryonic and postnatal maturation in animal models of ALS. We reported that SOD1(G85R) mutant mice exhibit specific delays in acquiring sensory-motor skills during the first week after birth. In addition, physiological measurements on in vitro spinal cord preparations reveal defects in evoking rhythmic activity with N-methyl-DL-aspartate and serotonin at lumbar, but not sacral roots. This is potentially significant, as functions involving sacral roots are spared at late stages of the disease. Moreover, electrical properties of SOD1 lumbar motoneurons are altered as early as the second postnatal week when mice begin to walk. Alterations concern the input resistance and the gain of SOD1 motoneurons which are lower than in control motoneurons. Whether or not the early changes in discharge firing are responsible for the uncoupling between motor axon terminals and muscles is still an open question. A link between these early electrical abnormalities and the late degeneration of motoneurons is proposed in this short review. Our data suggest that ALS, as other neurodegenerative diseases, could be a consequence of an abnormal development of neurons and network properties. We hypothesize that the SOD1 mutation could induce early changes during the period of maturation of motor systems and that compensatory mechanisms-linked to developmental spinal plasticity-might explain the late onset of the disease.