Current pathways for epidemiological research in amyotrophic lateral sclerosis

Evidence for the potential role of m6A modification in regulating autophagy in models of amyotrophic lateral sclerosis

Objective

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease. Research indicates that N6-methyladenosine (m6A) modification plays a crucial role in cellular autophagy during ALS development. This study investigates the role of autophagy in ALS, with a focus on the effect of messenger ribonucleic acid m6A methylation modification on disease progression.

Material and Methods

We compared m6A levels and regulatory molecule expressions in transgenic superoxide dismutase (SOD1)-G93A and non-transgenic mice, categorized into end-stage and control groups, using quantitative polymerase chain reaction and Western blotting. The NSC-34 cell line, which was modified to model ALS, enabled the investigation of apoptosis, autophagy, and autophagy disruption through terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assays, Western blotting, and fluorescent staining.

Results

Our findings indicate significantly elevated m6A methylation levels in ALS mice (0.262 ± 0.005) compared with the controls (0.231 ± 0.003) and in the ALS model cells (0.242±0.005) relative to those belonging to the wild-type control group (0.183 ± 0.007). Furthermore, the proteins involved in m6A RNA modification differed between groups, which suggest impaired autophagy flux in the ALS models.

Conclusion

These results suggest that m6A methylation may accelerate ALS progression through the disruption of autophagic processes. Our study underscores the role of m6A methylation in the pathology of ALS and proposes the targeting of m6A methylation as a potential therapeutic strategy for disease treatment. Although this study primarily used transgenic SOD1-G93A mice and NSC-34 cell models to investigate ALS pathology, potential differences in disease mechanisms between animal models and humans must be considered. Although a correlation was detected between m6A methylation levels and autophagy disruption in ALS, the study primarily established an association rather than provided detailed mechanistic insights.

Registration of Amyotrophic Lateral Sclerosis: Validity in the Danish National Patient Registry

Purpose

Health care databases are a valuable source for epidemiological research on amyotrophic lateral sclerosis (ALS) if diagnosis codes are valid. We evaluated the validity of the diagnostic codes for ALS in the Danish National Patient Registry (DNPR).

Patients and Methods

We obtained data from the DNPR for all adult (>17 years) patients registered with ALS in Denmark between 1987 and 2022 (median population of 4.2 million during the study period). We randomly selected adult patients living in the North Denmark Region and Central Denmark Region (median population 1.4 million), with a primary discharge diagnosis code of ALS, diagnosed at three departments of neurology. We retrieved and reviewed medical records and estimated the positive predictive value (PPV) of the ALS diagnosis.

Results

Over 36 years, we identified 5679 patients. From the validation cohort of 300 patients, we were able to retrieve 240 (80%) medical records, and 215 ALS diagnoses were confirmed. The overall positive predictive value was 89.6% (95% confidence interval (CI): 85.1-92.8). The highest PPV was achieved for diagnoses registered for patients aged ≥70 years (93.8; 95% CI: 86.2-97.3) compared to patients <60 years (83.4; 95% CI: 73.3-90.7).

Conclusion

We found a high PPV of primary diagnostic codes for ALS from Danish departments of neurology, demonstrating high validity. Thus, the DNPR is a well-suited data source for large-scale epidemiological research on ALS.

Medication use and risk of amyotrophic lateral sclerosis: using machine learning for an exposome-wide screen of a large clinical database

BACKGROUND

Accumulating evidence suggests that non-genetic factors have important etiologic roles in amyotrophic lateral sclerosis (ALS), yet identification of specific culprit factors has been challenging. Many medications target biological pathways implicated in ALS pathogenesis, and screening large pharmacologic datasets for signals could greatly accelerate the identification of risk-modulating pharmacologic factors for ALS.

METHOD

We conducted a high-dimensional screening of patients' history of medication use and ALS risk using an advanced machine learning approach based on gradient-boosted decision trees coupled with Bayesian model optimization and repeated data sampling. Clinical and medication dispensing data were obtained from a large Israeli health fund for 501 ALS cases and 4,998 matched controls using a lag period of 3 or 5 years prior to ALS diagnosis for ascertaining medication exposure.

RESULTS

Of over 1,000 different medication classes, we identified 8 classes that were consistently associated with increased ALS risk across independently trained models, where most are indicated for control of symptoms implicated in ALS. Some suggestive protective effects were also observed, notably for vitamin E.

DISCUSSION

Our results indicate that use of certain medications well before the typically recognized prodromal period was associated with ALS risk. This could result because these medications increase ALS risk or could indicate that ALS symptoms can manifest well before suggested prodromal periods. The results also provide further evidence that vitamin E may be a protective factor for ALS. Targeted studies should be performed to elucidate the possible pathophysiological mechanisms while providing insights for therapeutics design.

Factors associated with the time taken for diagnosis of amyotrophic lateral sclerosis (ALS) in Brazil. An online population-based inquiry

OBJECTIVE

This study evaluated factors associated with the time, in months, between the onset of symptoms and the diagnosis (time taken for diagnosis) of ALS for patients in Brazil, in the year 2014.

PATIENTS AND METHODS

An electronic questionnaire composed of 38 questions was developed and applied through internet-based social networks of patients. From the 210 replies, 194 were considered (86 from women, 108 from men). Most respondents were 51 to 60 years old. The Mann-Whitney test was used to compare the time taken for diagnosis between the strata of the sample.

RESULTS

The mean time taken for diagnosis was 14.21 (±16.87) months. There was a statistically significant difference only for higher education conditions (p = 0.009) and low education status (p = 0.042). There was no statistically significant difference between sexes, bulbar onset, age groups, and the presence of spouse, or 'partnership with ALS patients associations or exchange of experiences'.

CONCLUSION

These data suggest that the time taken for diagnosis of ALS is influenced by socioeconomic conditions that promote access to information and/or health services.

Occupational lead exposure and survival with amyotrophic lateral sclerosis

Objective: Lead exposure has been hypothesized to increase the risk of ALS, but only two studies have examined the association with ALS survival, and with inconsistent results. The use of occupational history to assess lead exposure can avoid reverse causation that may occur in epidemiologic analyses that use biomarkers of lead exposure collected after ALS onset.Methods: We evaluated the relationship of occupational lead exposure to ALS survival among 135 cases from an international ALS cohort that included deep phenotyping, careful follow-up, and questionnaires to quantify participants' occupation history. ALS patients were recruited in 2015-2019. We determined occupational lead exposure using a job-exposure matrix. We estimated hazard ratios (HR) and 95% confidence intervals (CI) for survival using Cox proportional hazard analysis with adjustment for covariates.Results: A total of 135 ALS patients completed the environmental questionnaires, among whom 38 reached a survival endpoint (death or permanent assisted ventilation). The median survival was 48.3 months (25th-75th percentile, 30.9-74.1). Older patients and those with initial symptom other than limb onset had shorter survival time. There were 36 ALS cases with occupational lead exposure. After adjusting for age, sex, site of onset, smoking, and military service, lead exposure was associated with an HR of 3.26 (95%CI 1.28-8.28). Results with adjustment for subsets of these covariates were similar.Conclusions: These results suggest that lead exposure prior to onset of ALS is associated with shorter survival following onset of ALS, and this association is independent of other prognostic factors.

The incidence and prevalence of motor neurone disease in South Australia

Background: Motor neurone disease (MND) is a neurodegenerative disease that leads to significant morbidity and mortality. The Global Burden of Disease (GBD) project estimated the MND all-age global prevalence is 4.5 (95% confidence interval (CI)=4.1-5.0) per 100,000 persons and the all-age incidence of 0.78 (95% CI = 0.71-0.86) per 100,000 person-years. Whether the prevalence and incidence of MND within South Australia using registry data is in keeping with these global estimates has not been studied. Objective: To describe the prevalence and annual incidence rates (IRs) of MND in South Australia between 2017 and 2019. Methods: A retrospective cohort study calculating the point prevalence of MND on 31 December 2017, 2018 and 2019 utilizing data from the Australasian Motor Neurone Disease Registry (AMNDR). The annual IRs between 2017 and 2019 were calculated using population data reported in the 2016 Australian census and age-standardized rates utilized the world population from the United Nations Population Division's World Population Prospects. Results: A total of 256 MND patients were identified, of whom 114 were alive on 31 December 2019. Based on the 2016 population of 1,676,653 persons, the estimated prevalence was 6.79 per 100,000 persons. The crude IR for the all-age South Australian population was 3.34 per 100,000 person-years (95% CI, 2.85-3.88). The estimated annual IRs based on those ≥20 yo were 4.98 (3.84-6.35), 3.68 (2.71-4.88), and 4.21 (3.17-5.49) per 100,000 person-years for 2017, 2018, and 2019, respectively. Conclusion: The crude prevalence and incidence of MND in South Australia were considerably higher than global estimates. This may reflect higher rates of the disease or higher rates of case ascertainment compared to the GBD project.

Amyotrophic Lateral Sclerosis: A Diet Review

Amyotrophic lateral sclerosis (ALS) is a fatal disease related to upper and lower motor neurons degeneration. Although the environmental and genetic causes of this disease are still unclear, some factors involved in ALS onset such as oxidative stress may be influenced by diet. A higher risk of ALS has been correlated with a high fat and glutamate intake and β-methylamino-L-alanine. On the contrary, a diet based on antioxidant and anti-inflammatory compounds, such as curcumin, creatine, coenzyme Q10, vitamin E, vitamin A, vitamin C, and phytochemicals could reduce the risk of ALS. However, data are controversial as there is a discrepancy among different studies due to a limited number of samples and the many variables that are involved. In addition, an improper diet could lead to an altered microbiota and consequently to an altered metabolism that could predispose to the ALS onset. In this review we summarized some research that involve aspects related to ALS such as the epidemiology, the diet, the eating behaviour, the microbiota, and the metabolic diseases. Further research is needed to better comprehend the role of diet and the metabolic diseases in the mechanisms leading to ALS onset and progression.

Case-control study in ALS using the National ALS Registry: lead and agricultural chemicals are potential risk factors

Objective: To identify occupational risk factors for ALS using well-characterized participants with ALS (P-ALS), sibling controls (S-controls), and matched population controls (P-controls) within the National ALS Registry. We also compared oxidative stress (OS) biomarkers between groups. Methods: P-ALS were recruited over 4 years. Demographic, socioeconomic, and medical data were ascertained from medical records and structured interviews. P-ALS were followed prospectively for 2 years or until death, whichever came sooner. S-controls and age-, sex-, race/ethnicity-, and residential location-matched P-controls were recruited over 3 years. Occupational exposure to lead and agricultural chemicals (ACs) were assigned by an occupational hygienist, blinded to case status. OS biomarkers in urine were measured. Results: P-ALS (mean age 62.8 years; 63% males) resided across the United States. Demographic and socioeconomic variables did not differ among P-ALS, S-controls, and P-controls. P-ALS were more likely to report occupations with exposure to lead (adjusted OR (aOR)=2.3, 95% CI 1.1, 4.6) and ACs (aOR = 2.4, 95% CI 1.2, 4.6) compared to pooled controls. Among those with occupations with exposure to both lead and ACs, aOR was 7.2 (95% CI 2.0, 26.1). Urinary 8-oxo-dG was significantly elevated among P-ALS (11.07 ± 5.42 ng/mL) compared to S-controls, P-controls, or pooled controls (pooled 7.43 ± 5.42 ng/mL; p < 0.0001) but was not associated with occupational exposure to either lead or ACs. Conclusions: Findings reveal increased risk of ALS diagnosis among those with occupational exposure to lead and ACs and increased OS biomarkers among cases compared to controls. OS may be an important pathogenic mechanism in ALS.

Environmental and Occupational Risk Factors of Amyotrophic Lateral Sclerosis: A Population-Based Case-Control Study

Objectives: Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease with still unknown etiology. We aimed at investigating the association between environmental and occupational factors with ALS risk. Methods: We performed a population-based case-control study in four Italian provinces (Catania, Modena, Novara, and Reggio Emilia) by administration of tailored questionnaires to ALS cases (n = 95) and randomly selected population referents (n = 135). We estimated ALS risk by calculating the odds ratio (OR) with its 95% confidence interval (CI) using an unconditional logistic regression model. Results: We found a positive association with disease risk for history of occupation in the agricultural sector (OR = 2.09, 95% CI 0.79-7.54), especially for longer than 10 years (OR = 2.72, 95% 1.02-7.20). Overall occupational exposure to solvents also suggested a positive association, especially for thinners (OR = 2.27, 95% CI 1.14-4.54) and paint removers (OR = 2.01, 95% CI 0.90-4.48). Both occupational and environmental exposure to electromagnetic fields show a slightly increased risk with OR = 1.69 (95% CI 0.70-4.09) and 2.41 (95% CI 1.13-5.12), respectively. Occupational but not environmental exposure to pesticides (OR = 1.22, 95% CI 0.63-2.37), particularly fungicides, and exposure to metals (OR = 4.20, 95% CI 1.88-9.38), particularly lead, mercury, and selenium, showed an imprecise but positive association. Finally, there was an indication of increased risk for living in proximity to water bodies. Conclusions: Despite the caution that needs to be used due to some study limitations, such as the low number of exposed subjects and the possibility of recall bias, these results suggest the potential role of some environmental and occupational factors in ALS etiology.

Energy Balance as a Moderator of Neurologic Disease Risk and Progression

Amyotrophic lateral sclerosis (ALS) is a devastating disease that like multiple other neurologic diseases has no curative treatment currently available. Environmental exposures to known neurotoxic compounds (e.g., pesticides, heavy metals, cyanobacterial toxins, etc.) are identified as risk factors associated with ALS. Assuming these environmental factors have causative roles in disease risk and given the ubiquity of these types of exposures for the modern human, why are not more people afflicted with ALS? Herein is proposed an energy balance moderation framework (EBMF)-a framework that postulates energy balance as a key moderator of neurologic disease risk. The EBMF proposes that the ability of the body to handle toxic compound exposures through excretion, metabolism, and/or storage impacts the acute and chronic tissue-specific toxicity which is moderated by energy balance. In this model, positive energy balance (weight gain or excess body weight/mass) would be protective against acute neurotoxic exposure permitting the assimilation and sequestration of toxic compounds within body stores separate from the nervous system. However, this protective buffering could be lost during sustained negative energy balance (weight loss) with the release of sequestered compounds redistributing to the nervous system. The EBMF may have relevance beyond ALS for other neurologic diseases with demonstrated environmental risks (such as Alzheimer's and Parkinson's disease) and offers new insights into potential strategies to reduce disease risk and develop novel treatments.

Clinical and Lifestyle Factors and Risk of Amyotrophic Lateral Sclerosis: A Population-Based Case-Control Study

Background: Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease of the motor neurons. The etiology of ALS remains largely unknown, particularly with reference to the potential environmental determinants. Methods: We performed a population-based case-control study in four provinces from both Northern and Southern Italy in order to assess non-genetic ALS risk factors by collecting through tailored questionnaires information about clinical and lifestyle factors. We estimated ALS risk by calculating odds ratio (OR) with its 95% confidence interval (CI) using unconditional logistic regression models adjusted for sex, age and educational attainment. Results: We recruited 230 participants (95 cases and 135 controls). We found a possible positive association of ALS risk with trauma, particularly head trauma (OR = 2.61, 95% CI 1.19–5.72), electric shock (OR = 2.09, 95% CI 0.62–7.06), and some sports, although at a competitive level only. In addition, our results suggest an increased risk for subjects reporting use of private wells for drinking water (OR = 1.38, 95% CI 0.73–2.27) and for use of herbicides during gardening (OR = 1.95, 95% CI 0.88–2.27). Conversely, there was a suggestion of an inverse association with overall fish consumption (OR = 0.27, 95% CI 0.12–0.60), but with no dose-response relation. Consumption of some dietary supplements, namely those containing amino acids and, in the Southern Italy population, vitamins and minerals such as selenium, seemed associated with a statistically imprecise increased risk. Conclusions: Our results suggest a potential etiologic role a number of clinical and lifestyle factors with ALS risk. However, caution is needed due to some study limitations. These include the small sample size and the low number of exposed subjects, which affect statistical precision of risk estimates, the potential for exposure misclassification, and the uncertainties about mechanisms underpinning the possible association between these factors and disease risk.

Synergistic toxicity in an in vivo model of neurodegeneration through the co-expression of human TDP-43M337V and tauT175D protein

Although it has been suggested that the co-expression of multiple pathological proteins associated with neurodegeneration may act synergistically to induce more widespread neuropathology, experimental evidence of this is sparse. We have previously shown that the expression of Thr¹⁷⁵Asp-tau (tau^T175D) using somatic gene transfer with a stereotaxically-injected recombinant adeno-associated virus (rAAV9) vector induces tau pathology in rat hippocampus. In this study, we have examined whether the co-expression of human tau^T175D with mutant human TDP-43 (TDP-43^M337V) will act synergistically. Transgenic female Sprague-Dawley rats that inducibly express mutant human TDP-43^M337V using the choline acetyltransferase (ChAT) tetracycline response element (TRE) driver with activity modulating tetracycline-controlled transactivator (tTA) were utilized in these studies. Adult rats were injected with GFP-tagged tau protein constructs in a rAAV9 vector through bilateral stereotaxic injection into the hippocampus. Injected tau constructs were: wild-type GFP-tagged 2N4R human tau (tau^WT; n = 8), GFP-tagged tau^T175D 2N4R human tau (tau^T175D, pseudophosphorylated, toxic variant, n = 8), and GFP (control, n = 8). Six months post-injection, mutant TDP-43^M337V expression was induced for 30 days. Behaviour testing identified motor deficits within 3 weeks after TDP-43 expression irrespective of tau expression, though social behaviour and sensorimotor gating remained unchanged. Increased tau pathology was observed in the hippocampus of both tau^WT and tau^T175D expressing rats and tau^T175D pathology was increased in the presence of cholinergic neuronal expression of human TDP-43^M337V. These data indicate that co-expression of pathological TDP-43 and tau protein exacerbate the pathology associated with either individual protein.

Spatial analyses of ALS incidence in Denmark over three decades

OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the motor neuron with very few known risk factors. We conducted a spatial epidemiologic analysis of ALS incidence in Denmark to assess the contribution of sociodemographic determinants to geographic variation.

METHODS

We analyzed 4249 ALS cases (1982-2013), each with 100 controls matched on sex and birth year. Odds ratio and 95% confidence bands at birth and diagnosis/index locations were calculated using generalized additive models. We included a bivariate spatial smooth for location in our conditional logistic regression adjusted for socioeconomic status and marital status. We also conducted analyses adjusted for both birth and diagnosis addresses to separate location effects.

RESULTS

We observed significantly elevated ALS odds near Copenhagen for both the birth and diagnosis period analyses. Sociodemographic factors did not explain the observed patterns. When we further adjusted our spatial analyses by including both birth and diagnosis addresses, the significant area of elevated male ALS odds by birth address shifted to northwest Denmark away from Copenhagen, and there was little evidence of variation among women. Geographic variation at diagnosis differed between male and females, suggesting that patterns are not just due to regional variation in case ascertainment.

CONCLUSION

ALS incidence in Denmark is associated with both location at birth and diagnosis, suggesting that geographic variation may be due to exposures occurring at birth or closer to diagnosis, although the latter could relate to case ascertainment issues.

Magnetic fields exposure from high-voltage power lines and risk of amyotrophic lateral sclerosis in two Italian populations

The aetiology of amyotrophic lateral sclerosis (ALS), a rare and extremely severe neurodegenerative disease, has been associated with magnetic fields exposure. However, evidence for such a relation in the general population is weak, although the previous null results might also be due to exposure misclassification, or a relationship might exist only for selected subgroups. To test such a hypothesis we carried out a population-based case-control study in two Northern and Southern Italy regions, including 703 ALS cases newly diagnosed from 1998 to 2011 and 2737 controls randomly selected from the residents in the study provinces. Overall, we found that a residence near high-voltage power lines, within the corridors yielding a magnetic fields of ≥0.1 μT, was not associated with an excess disease risk, nor did we identify a dose-response relationship after splitting the exposed corridor according to the 0.1, 0.2 and 0.4 μT cut-points of exposure. These results were confirmed taking into account age at onset, period of diagnosis, sex, geographical area, and length of exposure. Overall, despite the residual possibility of unmeasured confounding or small susceptible subgroups not identified in our study, these results appear to confirm that the exposure to magnetic fields from power lines occurring in the general population is not associated with increased ALS risk.

Evaluating a Gene-Environment Interaction in Amyotrophic Lateral Sclerosis: Methylmercury Exposure and Mutated SOD1

PURPOSE OF REVIEW

Gene-environment (GxE) interactions likely contribute to numerous diseases, but are often difficult to model in the laboratory. Such interactions have been widely hypothesized for amyotrophic lateral sclerosis (ALS); recent controlled laboratory studies are discussed here and hypotheses related to possible mechanisms of action are offered. Using methylmercury exposure and mutated SOD1 to model the impacts of such an interaction, we interpret evidence about their respective mechanisms of toxicity to interrogate the possibility of additive (or synergistic) effects when combined.

RECENT FINDINGS

Recent work has converged on mechanisms of calcium-mediated glutamate excitotoxicity as a likely contributor in one model of a gene-environment interaction affecting the onset and progression of ALS-like phenotype. The current experimental literature on mechanisms of metal-induced neuronal injury and their relevant interactions with genetic contributions in ALS is sparse, but we describe those studies here and offer several integrative hypotheses about the likely mechanisms involved.

Increased Incidence of Amyotrophic Lateral Sclerosis in Polymyositis: A Nationwide Cohort Study

OBJECTIVE

Past studies have shown common pathologic characteristics and shared immunologic features between polymyositis (PM) and amyotrophic lateral sclerosis (ALS). To explore the potential relationship between the 2 diseases, we performed a nationwide cohort study.

METHODS

We identified all newly diagnosed patients with PM from Taiwan's Registry of Catastrophic Illness Database between January 1, 1998 and December 31, 2011. Each PM patient was matched to ≤5 control patients from the National Health Insurance Research Database by sex, age, and entry date. Cumulative incidence of ALS was calculated by the Kaplan-Meier method and compared using the log rank test. Cox hazard regression was used to calculate the hazard ratio of ALS.

RESULTS

A total of 1,778 PM patients and 8,124 control patients were enrolled. PM patients had a higher cumulative incidence of ALS (P < 0.001). There was a positive correlation in being diagnosed with ALS in patients previously diagnosed with PM when stratified by sex. Consistent trends were conserved across different age strata. The strength of this association remained statistically significant after adjusting for sex, age, and concomitant autoimmune diseases (hazard ratio 25.72 [95% confidence interval 2.95-224.58]; P = 0.003).

CONCLUSION

This study demonstrates that a diagnosis of PM increased the likelihood of a subsequent ALS diagnosis, independent of sex, age, and concomitant autoimmune diseases. Future studies are warranted to clarify the underlying biologic mechanisms and to translate them into clinical therapeutic options.

Prevalence of Amyotrophic Lateral Sclerosis - United States, 2012-2013

PROBLEM/CONDITION

Amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig's disease, is a progressive and fatal neuromuscular disease for which no cure or viable treatment has been identified. ALS, like most noncommunicable diseases, is not a nationally notifiable disease in the United States. The prevalence of ALS in the United States during 2010-2011 was estimated to be 3.9 cases per 100,000 persons in the general population. Updated prevalence estimates are needed to help monitor disease status, better understand etiology, and identify risk factors for ALS.

PERIOD COVERED

2012-2013.

DESCRIPTION OF SYSTEM

The National ALS Registry, established in 2009, collects data on ALS patients in the United States to better describe the incidence and prevalence of ALS, examine risk factors such as environmental and occupational exposures, and characterize the demographics of those living with ALS. To identify prevalent cases of ALS, data are compiled from four national administrative databases (maintained by the Centers for Medicare and Medicaid Services, the Veterans Health Administration, and the Veterans Benefits Administration). To identify cases not included in these databases and to better understand risk-factors associated with ALS and disease progression, the Registry also includes data that are collected from patients who voluntarily enroll and complete online surveys.

RESULTS

During 2012 and 2013, the Registry identified 14,713 and 15,908 persons, respectively, who met the surveillance case definition of ALS. The estimated ALS prevalence rate was 4.7 cases per 100,000 U.S. population for 2012 and 5.0 per 100,000 for 2013. Due to revisions to the algorithm and use of death data from the National Death Index, an updated prevalence estimate has been calculated retrospectively for October 19, 2010-December 31, 2011. This updated estimate showed a prevalence rate of 4.3 per 100,000 population and a total of 13,282 cases. Since the inception of the Registry, the pattern of characteristics (e.g., age, sex, and race/ethnicity) among persons with ALS have remained unchanged. Overall, ALS was more common among whites, males, and persons aged 60-69 years. The age groups with the lowest number of ALS cases were persons aged 18-39 years and those aged ≥80 years. Males had a higher prevalence rate of ALS than females overall and across all data sources. These findings remained consistent during October 2010-December 2013.

INTERPRETATION

The Registry is the only available data source that can be used to estimate the national prevalence for ALS in the United States. Use of both administrative national databases and self-report from patients enables a comprehensive approach to estimate ALS prevalence. The overall increase in the prevalence rate from 4.3 per 100,000 persons (revised) during 2010-2011 to 4.7 and 5.0 per 100,000 persons, respectively, during 2012-2013 likely is not an actual increase in the number of ALS cases. Rather, this increase might be attributed to improved case ascertainment due to the refinement of the algorithm used to identify definite ALS cases, along with an increased public awareness of the Registry. Registry estimates of ALS prevalence are consistent with findings from long-established ALS registries in Europe and from smaller-scale epidemiologic studies previously conducted in the United States.

PUBLIC HEALTH ACTIONS

Data collected by the National ALS Registry are being used to better describe the epidemiology of ALS in the United States and to help facilitate research. The combined approach of using national administrative databases and a self-enrollment web portal to collect data is novel and potentially could be used for other non-notifiable diseases such as Parkinson's disease or multiple sclerosis. Increased public awareness of the Registry might lead to more ALS cases being identified from the secure web portal (https://www.cdc.gov/als), which can ascertain cases apart from the national administrative databases. For example, in 2014, the ALS Ice Bucket Challenge, a social media-centered campaign, received extensive public visibility and created increased awareness of ALS. The Agency for Toxic Substances and Disease Registry (ATSDR) works closely with ALS advocacy and support groups, researchers, health care professionals, and others to promote the National ALS Registry and to identify all cases of ALS in the United States. In addition to estimating the prevalence of ALS, the Registry is being used to collect specimens from patient enrollees through a new biorepository, connect patient enrollees with new clinical trials and epidemiologic studies, and fund studies to help learn more about the etiology of ALS. Additional information about the National ALS Registry is available at http://www.cdc.gov/als or by calling toll-free at 1-877-442-9719.

Amyotrophic lateral sclerosis in Brazil: Case series and review of the Brazilian literature

Our objective was to systematically analyse the first series of cases of amyotrophic lateral sclerosis (ALS) in Minas Gerais and to review the Brazilian literature about clinical studies in ALS. This was a cross-sectional and descriptive study of a consecutive series of patients with probable or defined sporadic ALS according to the Awaji criteria, followed at two referral centres of Belo Horizonte (South-east Brazil). Patients underwent full clinical assessment. Comparisons of patient subgroups according to disease duration and initial presentation were performed. A systematic review was performed about Brazilian clinical studies in ALS. Results showed that of the 61 enrolled patients the male/female ratio was 1.6:1. The mean age at onset of symptoms was 54.9 years (SD ± 11.4). Mean age at diagnosis was 56.3 years (SD ± 11.1). Regarding the initial form of presentation, 43 cases (70.5%) were spinal, 12 cases (19.7%) were generalized and six cases (9.8%) were bulbar. Eight studies were found in the systematic review. In conclusion, the profile of our sample was similar to other national and international series, except for fewer cases of bulbar ALS in our series. There are few clinical studies of ALS in Brazil. The national data of prevalence and incidence are still uncertain.

Diabetes Mellitus, Obesity, and Diagnosis of Amyotrophic Lateral Sclerosis: A Population-Based Study

IMPORTANCE

Although prior studies have suggested a role of cardiometabolic health on pathogenesis of amyotrophic lateral sclerosis (ALS), the association with diabetes mellitus has not been widely examined. Amyotrophic lateral sclerosis is the most common motor neuron disorder. Several vascular risk factors have been associated with decreased risk for ALS. Although diabetes is also a risk factor for vascular disease, the few studies of diabetes and ALS have been inconsistent.

OBJECTIVE

To examine the association between diabetes and obesity, each identified through International Statistical Classification of Diseases, Eighth or Tenth Revision codes in a hospital registry, and ALS using data from the Danish National Registers.

DESIGN, SETTING, AND PARTICIPANTS

Population-based nested case-control study of 3650 Danish residents diagnosed as having ALS between January 1, 1982, and December 31, 2009, and 365,000 controls (100 for each ALS case) matched on age and sex. The analysis was conducted in September and October 2014.

MAIN OUTCOMES AND MEASURES

Adjusted odds ratio for ALS associated with diabetes or obesity diagnoses at least 3 years prior to the ALS diagnosis date.

RESULTS

When considering diabetes and our obesity indicator together, the estimated odds ratio for ALS was 0.61 (95% CI, 0.46-0.80) for diabetes and 0.81 (95% CI, 0.57-1.16) for obesity. We observed no effect modification on the association with diabetes by sex. We did find a significant modification by age at ALS diagnosis and age at first mention of diabetes in the hospital registers. The protective association was stronger with increasing age at ALS diagnosis (P = .01), and the odds ratio for first mention of diabetes was 1.66 (95% CI, 0.85-3.21) before age 40 years but 0.52 (95% CI, 0.39-0.70) for older ages. These results are consistent with different associations for type 1 vs type 2 diabetes.

CONCLUSIONS AND RELEVANCE

In this Danish nationwide study to investigate the association between diabetes and ALS diagnosis, our findings are in agreement with previous reports of a protective association between vascular risk factors and ALS and suggest that type 2 diabetes, but not type 1, is protective for ALS.

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.

Establishing the UK DNA Bank for motor neuron disease (MND)

In 2003 the Motor Neurone Disease (MND) Association, together with The Wellcome Trust, funded the creation of a national DNA Bank specific for MND. It was anticipated that the DNA Bank would constitute an important resource to researchers worldwide and significantly increase activity in MND genetic research. The DNA Bank houses over 3000 high quality DNA samples, all of which were donated by people living with MND, family members and non-related controls, accompanied by clinical phenotype data about the patients. Today the primary focus of the UK MND DNA Bank still remains to identify causative and disease modifying factors for this devastating disease.

Comparison of diagnoses of amyotrophic lateral sclerosis by use of death certificates and hospital discharge data in the Danish population

Because ALS is rare, large-scale studies are difficult. Hospital and death certificate data are valuable tools, but understanding of how well they capture cases is needed. We identified 3650 incident cases in the Danish National Patient Register (NPR) between 1982 and 2009, using ICD-8 (before 1994) or ICD-10 codes. Death certificates were obtained from the Danish Register of Causes of Death. We obtained medical records for 173 of the cases identified in the NPR and classified these according to the El Escorial criteria. We compared ALS identification from death certificates to hospital discharges, and both to medical records. Results showed that the sensitivity for use of death certificates was 84.2% (95% CI 82.9-85.5%) and was significantly higher for females, subjects younger than 77 years, and when coded with ICD-8. Using only the underlying cause of death resulted in significantly lower sensitivity. The estimated overall positive predictive value (PPV) was 82.0% (95% CI 80.0-83.8%). Sensitivity and PPV were similar compared with medical records. In conclusion, we found that use of hospital discharges and death certificates is highly reliable and, therefore, a valuable tool for ALS epidemiologic studies. The possible effects on findings of slight differences by age, gender, and ICD coding should be considered.

The Epidemiology of Amyotrophic Lateral Sclerosis in New Hampshire, USA, 2004-2007

BACKGROUND/AIMS

Trends in disease incidence and mortality can provide clues to disease etiology. Previously, we described a town in New Hampshire (N.H.), USA, with 25 times the expected incidence rate of amyotrophic lateral sclerosis (ALS). This study aimed to describe the incidence and mortality of ALS across the state to assess rates relative to other states and industrialized nations.

METHOD

A retrospective review of records from regional ALS centers, clinics and ALS organizations was conducted to obtain demographics and diagnostic details for patients diagnosed with ALS or primary lateral sclerosis in N.H. from January 2004 to December 2007. Data on mortality from review of death certificates were obtained for a similar time frame.

RESULTS

We identified 113 N.H. residents diagnosed with ALS in 2004-2007, yielding an age-standardized incidence rate ranging from 1.3 to 2.2 per 100,000 of the population per year. During the same period, the standardized mortality rate per 100,000 varied from 2.6 to 3.5. ALS was more common among men (ratio 1.6:1), who were more likely than women to have an earlier age at onset (59 ± 14.2 vs. 65 ± 11.8 years, p = 0.01).

CONCLUSION

While localized areas in N.H. with high ALS incidence rates have been reported previously, the overall incidence and mortality rates of ALS in N.H. are similar to those in other industrialized nations.

Risk factors for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease. It is typically fatal within 2-5 years of symptom onset. The incidence of ALS is largely uniform across most parts of the world, but an increasing ALS incidence during the last decades has been suggested. Although recent genetic studies have substantially improved our understanding of the causes of ALS, especially familial ALS, an important role of non-genetic factors in ALS is recognized and needs further study. In this review, we briefly discuss several major genetic contributors to ALS identified to date, followed by a more focused discussion on the most commonly examined non-genetic risk factors for ALS. We first review factors related to lifestyle choices, including smoking, intake of antioxidants, physical fitness, body mass index, and physical exercise, followed by factors related to occupational and environmental exposures, including electromagnetic fields, metals, pesticides, β-methylamino-L-alanine, and viral infection. Potential links between ALS and other medical conditions, including head trauma, metabolic diseases, cancer, and inflammatory diseases, are also discussed. Finally, we outline several future directions aiming to more efficiently examine the role of non-genetic risk factors in ALS.

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.

Thr175-phosphorylated tau induces pathologic fibril formation via GSK3β-mediated phosphorylation of Thr231 in vitro

We have previously shown that amyotrophic lateral sclerosis with cognitive impairment can be characterized by pathologic inclusions of microtubule-associated protein tau (tau) phosphorylated at Thr(175) (pThr(175)) in association with GSK3β activation. We have now examined whether pThr(175) induces GSK3β activation and whether this leads to pathologic fibril formation through Thr(231) phosphorylation. Seventy-two hours after transfection of Neuro2A cells with pseudophosphorylated green fluorescent protein-tagged 2N4R tau (Thr(175)Asp), phosphorylated kinase glycogen synthase kinase 3 beta (active GSK3β) levels were significantly increased as was pathologic fibril formation and cell death. Treatment with each of 4 GSK3β inhibitors or small hairpin RNA knockdown of GSK3β abolished fibril formation and prevented cell death. Inhibition of Thr(231) phosphorylation (Thr(231)Ala) prevented pathologic tau fibril formation, regardless of Thr(175) state, whereas Thr(231)Asp (pseudophosphorylated at Thr(231)) developed pathologic tau fibrils. Ser(235) mutations did not affect fibril formation, indicating an unprimed mechanism of Thr(231) phosphorylation. These findings suggest a mechanism of tau pathology by which pThr(175) induces GSK3β phosphorylation of Thr(231) leading to fibril formation, indicating a potential therapeutic avenue for amyotrophic lateral sclerosis with cognitive impairment.

Amyotrophic lateral sclerosis: a long preclinical period?

The onset of amyotrophic lateral sclerosis (ALS) is conventionally considered as commencing with the recognition of clinical symptoms. We propose that, in common with other neurodegenerations, the pathogenic mechanisms culminating in ALS phenotypes begin much earlier in life. Animal models of genetically determined ALS exhibit pathological abnormalities long predating clinical deficits. The overt clinical ALS phenotype may develop when safety margins are exceeded subsequent to years of mitochondrial dysfunction, neuroinflammation or an imbalanced environment of excitation and inhibition in the neuropil. Somatic mutations, the epigenome and external environmental influences may interact to trigger a metabolic cascade that in the adult eventually exceeds functional threshold. A long preclinical and subsequent presymptomatic period pose a challenge for recognition, since it offers an opportunity for protective and perhaps even preventive therapeutic intervention to rescue dysfunctional neurons. We suggest, by analogy with other neurodegenerations and from SOD1 ALS mouse studies, that vulnerability might be induced in the perinatal period.

Population-based surveillance of amyotrophic lateral sclerosis in New Jersey, 2009-2011

BACKGROUND

Limited epidemiological data exist about amyotrophic lateral sclerosis (ALS) in the United States (US). The Agency for Toxic Substances and Disease Registry maintains the National ALS Registry and funded state and metropolitan surveillance projects to obtain reliable, timely information about ALS in defined geographic areas.

METHODS

Neurologists submitted case reports for ALS patients under their care between January 1, 2009 and December 31, 2011 who were New Jersey residents. A medical record verification form and electromyogram (EMG) report were requested for a sample of case reports. Incidence rates were standardized to the 2000 US Standard Population.

RESULTS

The average crude annual incidence rate was 1.87 per 100,000 person-years, the average age-adjusted annual incidence rate was 1.67 per 100,000 person-years, and the point prevalence rate on December 31, 2011 was 4.40 per 100,000 persons. Average annual incidence rates and point prevalence rates were statistically higher for men compared with women; Whites compared with Blacks/African Americans and Asians; and non-Hispanics compared with Hispanics.

CONCLUSIONS

The project findings contribute new, population-based, state-specific information to epidemiological data regarding ALS. The findings are generally consistent with previously published surveillance studies conducted in the US and abroad.

Modification of the association between lead exposure and amyotrophic lateral sclerosis by iron and oxidative stress related gene polymorphisms

Our objective was to examine whether functional polymorphisms in hemochromatosis (HFE; H63D and C282Y), transferrin (TfC2), and glutathione-s-transferase Pi1 (GSTP1; Ile105Val) genes modify any lead-ALS association. We measured blood lead using atomic absorption spectroscopy and bone lead - a biomarker of cumulative lead exposure - using K-shell-X-ray fluorescence in 100 neurologist-confirmed ALS cases and 194 controls, the latter recruited as part of two separate studies; all subjects lived in New England. Participants were considered variant carriers or wild-type for each polymorphism. To assess effect modification, we included cross-product terms between lead biomarkers and each polymorphism in separate adjusted polytomous logistic regression models. Compared with wild-type, the odds ratio (OR) per 15.6 μg/g patella lead (interquartile range; IQR) was 8.24 (95% CI 0.94-72.19) times greater among C282Y variant carriers, and 0.34 (95% CI 0.15-0.78) times smaller among H63D variant carriers. Results were weaker for tibia lead. Compared with wild-type the OR per 2 μg/dl blood lead (IQR) was 0.36 (95% CI 0.19-0.68) times smaller among H63D variant carriers, and 1.96 (95% CI 0.98-3.92) times greater among GSTP1 variant carriers. In conclusion, we found that HFE and GSTP1 genotypes modified the association between lead biomarkers and ALS. Contrasting modification by the HFE polymorphisms H63D and C282Y may suggest that the modification is not simply the result of increased iron.

ALS Multicenter Cohort Study of Oxidative Stress (ALS COSMOS): study methodology, recruitment, and baseline demographic and disease characteristics

Abstract In a multicenter study of newly diagnosed ALS patients without a reported family history of ALS, we are prospectively investigating whether markers of oxidative stress (OS) are associated with disease progression. Methods utilize an extensive structured telephone interview ascertaining environmental, lifestyle, dietary and psychological risk factors associated with OS. Detailed assessments were performed at baseline and at 3-6 month intervals during the ensuing 30 months. Our biorepository includes DNA, plasma, urine, and skin. Three hundred and fifty-five patients were recruited. Subjects were enrolled over a 36-month period at 16 sites. To meet the target number of subjects, the recruitment period was prolonged and additional sites were included. Results showed that demographic and disease characteristics were similar between 477 eligible/non-enrolled and enrolled patients, the only difference being type of health insurance among enrolled patients. Sites were divided into three groups by the number of enrolled subjects. Comparing these three groups, the Columbia site had fewer 'definite ALS' diagnoses. This is the first prospective, interdisciplinary, in-depth, multicenter epidemiological investigation of OS related to ALS progression and has been accomplished by an aggressive recruitment process. The baseline demographic and disease features of the study sample are now fully characterized.

An exploratory study of serum creatinine levels in patients with amyotrophic lateral sclerosis

The etiology of amyotrophic lateral sclerosis (ALS) remains unknown, but existing data argue for a role of creatinine in ALS pathophysiology. Our aim is to clarify the correlation between serum creatinine and ALS in Chinese population. A total of 512 sporadic ALS (SALS) patients and 501 age- and gender-matched healthy controls were included. Revised ALS Functional Rating Scale (ALS-FRS-R) was used to assess the motor functional status of SALS patients. Survival analysis was performed using Kaplan-Meier method. Serum creatinine levels were significantly lower in SALS patients than in controls (p < 0.001). Patients with the second, the third and highest quartiles of creatinine levels had a significantly lower presence of ALS compared to those with the lowest quartile (p for trend <0.001). However, decreased presence of ALS was not found in the highest quartiles compared with the lowest quartiles in females. Sporadic ALS patients with different site of onset have similar serum creatinine levels, but underweight patients presented lower levels of serum creatinine. Patients with low serum creatinine levels are more likely to have severe motor impairment and low body mass index (BMI) values. This study demonstrates that SALS patients have lower serum creatinine levels than well-matched controls. Higher levels of serum creatinine are less likely to be associated with the presence of ALS in Chinese populations. Low serum creatinine levels may be related to severe motor impairment in SALS patients, after adjusting the confounding factor-BMI. However, serum creatinine has no deleterious impact on survival in ALS.

Amyotrophic lateral sclerosis and parkinsonism in Papua, Indonesia: 2001-2012 survey results

OBJECTIVE

Only one previous follow-up study of amyotrophic lateral sclerosis (ALS) and parkinsonism in Papua, Indonesia has been carried out since a survey undertaken in 1962-1981 by Gajdusek and colleagues. Therefore, to clarify the clinical epidemiology of ALS and parkinsonism in the southern coastal region of Papua, the clinical characteristics and prevalence of the diseases in this region were examined and assessed.

METHODS

Cases of ALS and parkinsonism were clinically examined during a 2001-2012 survey in Bade and other villages along the Ia, Edera, Dumut and Obaa rivers in Papua, Indonesia. Possible, probable and definite ALS was diagnosed clinically by certified neurologists based on El Escorial criteria. The criteria for a diagnosis of parkinsonism were the presence of at least two of the four following signs: tremor, rigidity, bradykinesia and postural impairment with a progressive course.

RESULTS

During the survey, 46 cases of ALS and/or parkinsonism were diagnosed within a population range of 7000 (2001-2002) to 13 900 (2007-2012). The 46 cases consisted of 17 probable-definite cases of ALS, including three with cognitive impairment (CI), 13 cases of overlapping possible, probable or definite ALS and parkinsonism, including five with CI, and 16 cases of parkinsonism, including one with CI. The crude point prevalence rate of pure ALS was estimated to be at least 73 (95% CI 0 to 156) to 133 (27 to 240)/100 000 people and that of overlapping ALS and parkinsonism at least 53 (0 to 126) to 98 (2 to 193)/100 000 in 2007, or 2010 in some regions.

CONCLUSIONS

While the prevalence of ALS in Papua has decreased over the past ∼30-35 years, it remains higher than the global average. There was a high prevalence of overlapping ALS, parkinsonism and CI, which has also been previously reported in Guam and Kii.

Epidemiology of amyotrophic lateral sclerosis in Emilia Romagna Region (Italy): A population based study

Our objective was to describe incidence and clinical features of ALS from a prospective population-based study in Emilia Romagna Region (ERR). From 2009 onwards, a prospective registry recorded all incident cases of ALS among residents in the ERR (population, 4.4 million inhabitants), involving 17 neurological departments. For each patient, detailed demographic and clinical information was collected by caring physicians. Results showed that from 1 January 2009 to 31 December 2011, 347 patients received a new diagnosis of ALS with a crude incidence rate of 2.63/100,000/year. There was micro-geographic heterogeneity throughout ERR, with higher incidence rates in the low density population (3.27/100,000) (p < 0.01). ALS patients have been more frequently employed in agriculture than the general ERR population (8.64% vs. 4.6%, p < 0.01). Clinical features were similar to those described in previous population based studies. In conclusion, we report incidence rates similar to those reported by European registries, reflecting good accuracy of our prospective study. We confirmed previous studies reporting higher incidence rates in rural areas and among agricultural workers. Although genetics has been gaining increasing importance in ALS aetiology, some epidemiological data are still unexplained. Identifying geographical areas or populations with high incidence rates can be a starting point for identifying environmental risk factors. Further studies having this specific aim can shed light on these topics.

Association analysis of four candidate genetic variants with sporadic amyotrophic lateral sclerosis in a Chinese population

Recently, four single nucleotide polymorphisms (SNPs), including rs2814707 in the 9p21, rs12608932 in the UNC13A gene, rs13048019 in the TIMA1 gene, and rs2228576 in the SCNN1A gene have been reported to be associated with the risk for developing amyotrophic lateral sclerosis (ALS) in Caucasian population. However, this association is not consistent among different studies and yet to be tested in ALS patients in Mainland China. This study included 397 sporadic ALS (SALS) patients and 287 unrelated Chinese healthy controls from Southwest China. Four SNPs listed above were genotyped by using Sequenom's iPLEX assay. No significant differences in the genotype distributions or minor allele frequencies in all SNPs were found between ALS group and control group, between the spinal-onset group and bulbar-onset group, and between the early-onset group and the late-onset group. Our results suggest that these SNPs are unlikely to be common cause of SALS in Chinese population.