The epidemiology of amyotrophic lateral sclerosis in the Mount Etna region: a possible pathogenic role of volcanogenic metals

Presymptomatic geographical distribution of ALS patients suggests the involvement of environmental factors in the disease pathogenesis

BACKGROUND

Given that the pathogenetic process of ALS begins many years prior to its clinical onset, examining patients' residential histories may offer insights on the disease risk factors. Here, we analyzed the spatial distribution of a large ALS cohort in the 50 years preceding the disease onset.

METHODS

Data from the PARALS register were used. A spatial cluster analysis was performed at the time of disease onset and at 1-year intervals up to 50 years prior to that.

RESULTS

A total of 1124 patients were included. The analysis revealed a higher-incidence cluster in a large area (435,000 inhabitants) west of Turin. From 9 to 2 years before their onset, 105 cases were expected and 150 were observed, resulting in a relative risk of 1.49 (P = 0.04). We also found a surprising high number of patients pairs (51) and trios (3) who lived in the same dwelling while not being related. Noticeably, these occurrences were not observed in large dwellings as we would have expected. The probability of this occurring in smaller buildings only by chance was very low (P = 0.01 and P = 0.04 for pairs and trios, respectively).

CONCLUSIONS

We identified a higher-incidence ALS cluster in the years preceding the disease onset. The cluster area being densely populated, many exposures could have contributed to the high incidence ALS cluster, while we could not find a shared exposure among the dwellings where multiple patients had lived. However, these findings support that exogenous factors are likely involved in the ALS pathogenesis.

Spatial clustering of amyotrophic lateral sclerosis in Sardinia, Italy: The contribution of age, sex, and genetic factors

INTRODUCTION/AIMS

Several microgeographic clusters of higher/lower incidence of amyotrophic lateral sclerosis (ALS) have been identified worldwide. Differences in the distribution of local factors were proposed to explain the excess ALS risk, whereas the contribution of known genetic/epigenetic factors remains unclear. The aim is to identify restricted areas of higher risk in Sardinia and to assess whether age, sex, and the most common causative genetic mutations in Sardinia (C9orf72 and TARDBP mutations) contributed to the variation in the ALS risk.

METHODS

We performed an ad hoc analysis of the 10-y population-based incident cohort of ALS cases from a recent study of a large Sardinian area. Cluster analysis was performed by age- and sex-adjusted Kulldorff's spatial scan statistic.

RESULTS

We identified a statistically significant cluster of higher ALS incidence in a relatively large area including 34 municipalities and >100,000 individuals. The investigated genetic mutations were more frequent in the cluster area than outside. Regardless of the genetic mutations, the excess of ALS risk was significantly associated with either sex or with age ≥ 65 y. Finally, an additive interaction between older age and male sex contributed to the excess of ALS risk in the cluster area but not outside.

DISCUSSION

Our analysis demonstrated that known genetic factors, age, and sex may contribute to microgeographic variation in ALS incidence. The significant additive interaction between older age and male sex we found in the high-incidence cluster could suggest the presence of a third factor connecting the analyzed risk factors.

Risk factors associated with amyotrophic lateral sclerosis based on the observational study: a systematic review and meta-analysis

Objective

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder affecting the upper and lower motor neurons. Though the pathogenesis of ALS is still unclear, exploring the associations between risk factors and ALS can provide reliable evidence to find the pathogenesis. This meta-analysis aims to synthesize all related risk factors of ALS to understand this disease comprehensively.

Methods

We searched the following databases: PubMed, EMBASE, Cochrane library, Web of Science, and Scopus. Moreover, observational studies, including cohort studies, and case-control studies, were included in this meta-analysis.

Results

A total of 36 eligible observational studies were included, and 10 of them were cohort studies and the rest were case-control studies. We found six factors exacerbated the progression of disease: head trauma (OR = 1.26, 95% CI = 1.13, 1.40), physical activity (OR = 1.06, 95% CI = 1.04, 1.09), electric shock (OR = 2.72, 95% CI = 1.62, 4.56), military service (OR = 1.34, 95% CI = 1.11, 1.61), pesticides (OR = 1.96, 95% CI = 1.7, 2.26), and lead exposure (OR = 2.31, 95% CI = 1.44, 3.71). Of note, type 2 diabetes mellitus was a protective factor for ALS. However, cerebrovascular disease (OR = 0.99, 95% CI = 0.75, 1.29), agriculture (OR = 1.22, 95% CI = 0.74, 1.99), industry (OR = 1.24, 95% CI = 0.81, 1.91), service (OR = 0.47, 95% CI = 0.19, 1.17), smoking (OR = 1.25, 95% CI = 0.5, 3.09), chemicals (OR = 2.45, 95% CI = 0.89, 6.77), and heavy metal (OR = 1.5, 95% CI = 0.47, 4.84) were not risk factors for ALS based on meta-analyses.

Conclusions

Head trauma, physical activity, electric shock, military service, pesticides, and lead were risk factors for ALS onset and progression. But DM was a protective factor. This finding provides a better understanding of ALS risk factors with strong evidence for clinicians to rationalize clinical intervention strategies.

INPLSY registration number

https://inplasy.com/inplasy-2022-9-0118/, INPLASY202290118.

Metal ratios as possible biomarkers for amyotrophic lateral sclerosis

BACKGROUND AND OBJECTIVES

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with unknown aetiology. Metals have been suspected to contribute to ALS pathogenesis since mid-19th century, yet studies on measured metal concentrations in ALS patients have often yielded conflicting results, with large individual variation in measured values. Calculating metal concentration ratios can unveil possible synergistic effects of neurotoxic metals in ALS pathogenesis. The aim of this study was to investigate if ratios of different metal concentrations in cerebrospinal fluid (CSF) and blood plasma, respectively, differ between ALS patients and healthy controls.

METHODS

Cerebrospinal fluid and blood plasma were collected from 17 ALS patients and 10 controls. Samples were analysed for 22 metals by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), and all possible 231 metal ratios calculated in each body fluid.

RESULTS

Fifty-three metal ratios were significantly elevated in ALS cases as compared to controls (p < 0.05); five in blood plasma, and 48 in CSF. The finding of fewer elevated ratios in blood plasma may indicate specific transport of metals into the central nervous system. The elevated metal ratios in CSF include Cd/Se (p = 0.031), and 16 ratios with magnesium, such as Mn/Mg (p = 0.005) and Al/Mg (p = 0.014).

CONCLUSION

Metal ratios may be used as biomarkers in ALS diagnosis and as guidelines for preventive measures.

Early-onset, conjugal, twin-discordant, and clusters of sporadic ALS: Pathway to discovery of etiology via lifetime exposome research

The identity and role of environmental factors in the etiology of sporadic amyotrophic lateral sclerosis (sALS) is poorly understood outside of three former high-incidence foci of Western Pacific ALS and a hotspot of sALS in the French Alps. In both instances, there is a strong association with exposure to DNA-damaging (genotoxic) chemicals years or decades prior to clinical onset of motor neuron disease. In light of this recent understanding, we discuss published geographic clusters of ALS, conjugal cases, single-affected twins, and young-onset cases in relation to their demographic, geographic and environmental associations but also whether, in theory, there was the possibility of exposure to genotoxic chemicals of natural or synthetic origin. Special opportunities to test for such exposures in sALS exist in southeast France, northwest Italy, Finland, the U.S. East North Central States, and in the U.S. Air Force and Space Force. Given the degree and timing of exposure to an environmental trigger of ALS may be related to the age at which the disease is expressed, research should focus on the lifetime exposome (from conception to clinical onset) of young sALS cases. Multidisciplinary research of this type may lead to the identification of ALS causation, mechanism, and primary prevention, as well as to early detection of impending ALS and pre-clinical treatment to slow development of this fatal neurological disease.

Spatio-temporal clustering of amyotrophic lateral sclerosis in France: A population-based study

OBJECTIVE

To assess spatial aggregates of amyotrophic lateral sclerosis (ALS) incident cases, using a solid geo-epidemiological statistical method, in France.

METHODS

This population-based study (2003-2011) investigated 47.1 million person-years of follow-up (PYFU). Case ascertainment of incident ALS cases was based on multiple sources (ALS referral centers, hospital centres and health insurance data). Neurologists confirmed all ALS diagnoses. Exhaustiveness was estimated through capture-recapture. Aggregates were investigated in four steps: (a) geographical modelling (standardized incidence ratio (SIR) calculation), (b) analysis of the spatial distribution of incidence (Phothoff-Winttinghill's test, Global Moran's Index, Kulldorf's spatial scan statistic, Local Moran's Index), (c) classification of the level of certainty of spatial aggregates (i.e. definite cluster; probable over-incidence area; possible over-incidence area) and (d) evaluation of the robustness of the results.

RESULTS

The standardized incidence of ALS was 2.46/100,000 PYFU (95% CI 2.31-2.63, European population as reference) based on 1199 incident cases. We identified 13 areas of spatial aggregates: one cluster (stable in robustness analysis), five probable over-incidence areas (2 stable in robustness analysis) and seven possible over-incidence areas (including 4 stable areas in robustness analysis). A cluster was identified in the Rhône-Alpes region: 100 observed vs 54.07 expected cases for 2,411,514 PYFU, SIR: 1.85 (95% CI 1.50-2.25).

CONCLUSION

We report here one of the largest investigations of incidence and spatial aggregation of ALS ever performed in a western country. Using a solid methodology framework for case ascertainment and cluster analysis, we identified 13 areas that warrant further investigation.

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.

Incidence, survival and geoepidemiological analysis of meningiomas and glioblastomas in the province of Catania during the 2003-2016 period

BACKGROUND

Meningiomas are the most common primary brain tumors, followed by glioblastomas. Nevertheless, no previous studies have been conducted to evaluate the epidemiology of meningiomas and glioblastomas in the southern region of Italy. Thus, the aim of our study was to evaluate incidence, temporal trend and survival rate of meningiomas and glioblastomas in the province of Catania during the study period. Moreover, a geoepidemiological analysis was performed in order to identify possible geographical and temporal clusters.

METHODS

All subjects with meningiomas and glioblastomas diagnosed from 2003 to 2016 in the province of Catania were collected, using the local cancer registry. Incidence rate (IR) was calculated by gender, age-groups and tumor behavior. Temporal changes in incidence trend were assessed using a Joinpoint regression analysis while survival analysis was performed using Kaplan-Meier method. Cluster analysis was performed using Kulldorff's spatial scan statistic.

RESULTS

In the province of Catania, a total of 1488 cases of meningiomas and 443 cases of glioblastomas were identified from 2003 to 2016, with an IR of 9.8/100,000 person-years (95%CI 9.3-10.3) and 2.9/100,000 person-years (95%CI 2.7-3.2), respectively. Meningiomas were more common among women (p-value<0.0001), while glioblastomas among men (p-value<0.0001). IR progressively increased over the ages, reaching a peak in the 75-84 and 65-74 years-old group in, respectively, meningiomas and glioblastomas. Mean survival was higher in subjects diagnosed with meningiomas as compared to those with glioblastomas (10.7 years and 15.8 months, respectively), with age as the strongest risk factor for death. Spatial and space-time cluster of high incidence of meningiomas was detected in a small community on the eastern flank of the Mt. Etna volcano.

CONCLUSIONS

Epidemiology of meningioma and glioblastoma in the province of Catania is close to that reported worldwide. Spatial and space-time cluster of meningiomas were found in Pedara. Further studies on risks factor are necessary.

Identification by MicroRNA Analysis of Environmental Risk Factors Bearing Pathogenic Relevance in Non-Smoker Lung Cancer

MicroRNA and DNA adduct biomarkers may be used to identify the contribution of environmental pollution to some types of cancers. The aim of this study was to use integrated DNA adducts and microRNAs analyses to study retrospectively the contribution of exposures to environmental carcinogens to lung cancer in 64 non-smokers living in Sicily and Catania city near to the Etna volcano. MicroRNAs were extracted from cancer lung biopsies, and from the surrounding lung normal tissue. The expression of 2549 human microRNAs was analyzed by microarray. Benzo(a)Pyrene-DNA adducts levels were analyzed in the patients’ blood by HPLC−fluorescence detection. Correlations between tetrols and environmental exposures were calculated using Pearson coefficients and regression variable plots. Compared with the healthy tissue, 273 microRNAs were downregulated in lung cancer. Tetrols levels were inversely related both with the distance from Etna and years since smoking cessation, but they were not significantly correlated to environmental exposures. The analysis of the microRNA environmental signatures indicates the contribution of environmental factors to the analyzed lung cancers in the following decreasing rank: (a) car traffic, (b) passive smoke, (c) radon, and (d) volcano ashes. These results provide evidence that microRNA analysis can be used to retrospectively investigate the contribution of environmental factors in human lung cancer occurring in non-smokers.

Estimated Prevalence and Incidence of Amyotrophic Lateral Sclerosis and SOD1 and C9orf72 Genetic Variants

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a rare neurological disorder characterized by progressive deterioration of motor neurons. Assessment of the size/geographic distribution of the ALS population, including ALS with genetic origin, is needed to understand the burden of the disease and the need for clinical intervention and therapy.

OBJECTIVES

The main objective of this study was to estimate the number of prevalent and incident ALS cases overall and superoxide dismutase 1 (SOD1) and chromosome 9 open reading frame 72 (C9orf72) ALS in 22 countries across Europe (Belgium, France, Germany, Ireland, Italy, Netherlands, Norway, Russia, Spain, Sweden, and UK), North America (USA and Canada), Latin America (Argentina, Brazil, Colombia, Mexico, and Uruguay), and Asia (China, Japan, South Korea, and Taiwan).

METHODS

A comprehensive literature search was conducted to identify population-based studies reporting ALS prevalence and/or incidence rates. Pooled prevalence and incidence rates were obtained using a meta-analysis approach at the country and regional geographic level. A country-level pooled estimate was used when ≥2 studies were available per country and geographic regional pooled estimates were used otherwise. The proportion of cases with a SOD1 or C9orf72 mutation among sporadic (sALS) and familial (fALS) cases were obtained from a previous systematic review and meta-analysis.

RESULTS

Pooled prevalence rates (per 100,000 persons) and incidence rates (per 100,000 person-years) were 6.22 and 2.31 for Europe, 5.20 and 2.35 for North America, 3.41 and 1.25 for Latin America, 3.01 and 0.93 for Asian countries excluding Japan, and 7.96 and 1.76 for Japan, respectively. Significant heterogeneity in reported incidence and prevalence was observed within and between countries/geographic regions. The estimated number of 2020 ALS cases across the 22 countries is 121,028 prevalent and 41,128 incident cases. The total estimated number of prevalent SOD1 cases is 2,876 cases, of which, 1,342 (47%) were fALS and 1,534 (53%) were sALS, and the number of incident SOD1 cases is 946 (434 [46%] fALS and 512 [54%] sALS). The total estimated number of prevalent C9orf72 cases is 4,545 (1,198 [26%] fALS, 3,347 [74%] sALS), and the number of incident C9orf72 cases is 1,706 (450 [26%] fALS and 1,256 [74%] sALS).

DISCUSSION

The estimated number of patients with SOD1 and C9orf72 ALS suggests that although the proportions of SOD1 and C9orf72 are higher among those with fALS, the majority of SOD1 and C9orf72 ALS cases may be found among those with sALS (about 53 and 74%, respectively). These results suggest that classification of fALS based on reported family history does not capture the full picture of ALS of genetic origin.

Exposure to emissions from Mount Etna (Sicily, Italy) and incidence of thyroid cancer: a geographic analysis

An increased incidence of thyroid cancer has been reported in the area close to Mount Etna, the largest volcano in Europe located in Northeastern Sicily. We tested the hypothesis that exposure to the emissions from the volcano is associated with thyroid cancer in 186 municipalities from three provinces surrounding the volcano (1.9 million inhabitants). We measured the angle between the bearing of the municipalities and each direction, with special focus on South-East, the prevalent direction of the plume, and conducted a regression analysis on 2003–2016 incidence rates of thyroid cancer, adjusting for distance from Mount Etna, population size, and income. A 10-degree increase in the angle with South-East was associated with a decrease in thyroid cancer rates in the whole population (− 0.67 cases/100,000, p = 0.002) and in women (− 1.54/100,000, p < 0.001), and were robust to several sensitivity analyses. Similar results were obtained for East-South-East direction. These results support the hypothesis of a potential role of exposure to the plume from Mount Etna in determining the high rates of thyroid cancer. The results need to be confirmed in analytical studies, in which information of exposure to chemicals originating from the volcano, as well as other possible causes, should be carefully measured, molecular characteristics of the tumors and taken into account.

Can volcanic trace elements facilitate Covid-19 diffusion? A hypothesis stemming from the Mount Etna area, Sicily

In December 2019, severe cases of pneumonia of unknown aetiology were reported in Wuhan city, in China. Lately, the pneumonia was related to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), and the diseases was termed coronavirus disease-2019 (COVID-19). At the end of January 2020, the infection spread all over Italy, but with high infection rates and mortality in the northern part, especially in Lombardy, the most industrialized and polluted region of the country. It is noteworthy that a strong association between severe viral respiratory disease and air pollution has been described. Air pollutant could be solid particles, liquid droplets, or gases and can be of natural origin (such as ash from a volcanic eruption) or released from motor vehicle depletes (carbon monoxide gas) or factories (sulfur dioxide). Volcanic eruptions release large amounts of sulphuric acid, hydrogen sulfide, and hydrochloric acid into the atmosphere. Pulmunary diseases spreadby means of small droplets in thebreath, also called aerosols, and air pollution may facilitate the outside survival of viruses. We suppose that ash and gases emitted from the Mount Etna contributed to air pollution, potentially favouring the major contagion of COVID-19 in the eastern flank of the mountain, as in Catania city. In fact, ash and gases (with regard to radon) are usually particularly intense in winter, with a reduction of emission of specific metals with warmer weather. This is the first paper that elaborates the hypothesis of a potential role of volcanic gases and heavy metals-related air pollution, combined to specific climatic conditions and regional topography, in favouring severe COVID-19 diffusion in Sicily. Clinical and epidemiological studies are needed to support the hypothesis and plan the due prevention and awareness-raising campaigns.

Comparison of exosomes derived from induced pluripotent stem cells and mesenchymal stem cells as therapeutic nanoparticles for treatment of corneal epithelial defects

Induced pluripotent stem cells and mesenchymal stem cells are pluripotent stem cells that represent promising therapies for treating various tissue injuries and wound healing. Exosomes are nanosized extracellular vesicles that have been identified as important mediators of therapeutic functions, which are performed via cell communication. In this study, we compared the efficacy of induced pluripotent stem cells-derived exosomes (iPSCs-Exos) and mesenchymal stem cells-derived exosomes (MSCs-Exos) in treating corneal epithelial defects. The characteristics of the two types of exosomes were not significantly different. Compared to MSCs-Exos, iPSCs-Exos had a better in vitro effect on the proliferation, migration, cell cycle promotion and apoptosis inhibition of human corneal epithelial cells. iPSCs/MSCs-Exos promoted cell regeneration by upregulating cyclin A and CDK2 to drive HCECs to enter the S phase from the G0/G1 phase. In vivo results from a corneal epithelial defect model showed that both iPSCs-Exos and MSCs-Exos accelerated corneal epithelium defect healing while the effects of iPSCs-Exos were much stronger than those of MSCs-Exos. This study demonstrated that iPSCs-Exos had a better therapeutic effect on corneal epithelial defect healing. Thus, a novel potential nanotherapeutic strategy for treating corneal epithelial defects and even more ocular surface disease could be undertaken by using iPSCs-Exos dissolved in eye drops.

Amyotrophic lateral sclerosis and lead: A systematic update

Heavy metals are considered to be among the leading environmental factors that trigger amyotrophic lateral sclerosis (ALS). However, no convincing biopathological mechanism and therapeutic clinical implication of such metals in ALS pathogenesis have been established. This is partly attributable to the technical and scientific difficulties in demonstrating a direct and causative role of heavy metals in the onset of ALS in patients. However, a body of epidemiological, clinical and experimental evidences suggest that lead (Pb), more than other metals, could actually play a major role in the onset and progression of ALS. Here, to clarify the nature of the association and the causative role of Pb in ALS, we comprehensively reviewed the scientific literature of the last decade with objective database searches and the methods typically adopted in systematic reviews, critically analysing and summarising the various scientifically sound evidence on the relationship between ALS and Pb. From these tasks, we noted a number of multidisciplinary associations between ALS and Pb, and specifically the importance of occupational exposure to Pb in ALS development and/or progression. We also report the possible involvement of TAR DNA binding protein (TDP-43)-based molecular mechanism in Pb-mediated ALS, although these data rely on a single study, which included both in vitro experiments and an animal model, and are therefore still preliminary. Finally, we briefly examined whether this knowledge could inspire new targeted therapies and policies in the fight against ALS.

CSF neurotoxic metals/metalloids levels in amyotrophic lateral sclerosis patients: comparison between bulbar and spinal onset

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of the central nervous system (CNS) that causes progressive and irreversible damage in motor neurons. Different causal hypotheses include genetic, viral, traumatic and environmental mechanisms, such as exposure to heavy metals. The aim of this study was to compare metal/metalloid levels in cerebro-spinal fluid of ALS subtypes (spinal vs bulbar clinical onset).

MATERIAL AND METHODS

This observational study consecutively screened all ALS patients referring to the Neurology Clinic of the University of Catania (Italy). Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify magnesium (Mg), cuprum (Cu), selenium (Se), iron (Fe), manganese (Mn), vanadium (V), zinc (Zn), alluminium (Al), arsenic (As), cobalt (Co), nickel (Ni), mercury (Hg), lead (Pb), cadmium (Cd) and palladium (Pd) levels.

RESULTS

Thirty-seven patients were enrolled (62.2% females), median age of 65 years (IQR: 59-71 years). Thirty-one (83.8%) patients had a spinal onset and 6 (16.2%) a bulbar onset. Se and As levels were higher compared to the reference values (RV) both in spinal and bulbar onset, while Cu was higher than RV only in bulbar onset. Moreover, Cu (129.8 μg/L vs 29.8 μg/L), Fe (54.5 μg/L vs 33.3 μg/L), Mn (3.4 μg/L vs 1.8 μg/L), Zn (46.1 μg/L vs 35.7 μg/L), Al (12.2 μg/L vs 6.7 μg/L), Ni (2.80 μg/L vs 1.40 μg/L), and Pb (0.60 μg/L vs 0.30 μg/L) levels were higher in bulbar than in spinal onset, conversely As was slightly higher in spinal than in bulbar onset (1.40 μg/L vs 1.10 μg/L). Overall, Cu (129 μg/L vs 31 μg/L), Fe (92.2 μg/L vs 32.9 μg/L), Mn (3.35 μg/L vs 1.80 μg/L), Zn (56.5 μg/L vs 35.2 μg/L), Al (14.45 μg/L vs 6.70 μg/L), and Cd (0.40 μg/L vs 0.08 μg/L) levels were higher in patients with disease duration less than 19 months.

CONCLUSION

Our results supported the hypothesis that metals/metalloids with neurotoxic effects could be involved in the etiology of ALS, showing higher levels of Cu, Se and As. Relevant differences in Cu and Mn levels were found between bulbar and spinal onset patients.

Living near waterbodies as a proxy of cyanobacteria exposure and risk of amyotrophic lateral sclerosis: a population based case-control study

BACKGROUND

Epidemiological studies highlighted the possibility that exposure to cyanotoxins leads to the development of the neurodegenerative disease amyotrophic lateral sclerosis (ALS).

METHODS

We devised a population-based case-control study in two Italian populations. We used residential proximity of the residence to water bodies as a measure of possible exposure to cyanotoxins.

RESULTS

Based on 703 newly-diagnosed ALS cases and 2737 controls, we calculated an ALS odds ratio (OR) of 1.41 (95% CI: 0.72-2.74) for current residence in the vicinity of water bodies, and a slightly lower estimate for historical residence (OR: 1.31; 95% CI: 0.57-2.99). Subjects <65 years and people living in the Northern Italy province of Modena had higher ORs, especially when historical residence was considered.

CONCLUSIONS

Overall, despite some risk of bias due to exposure misclassification and unmeasured confounding, our results appear to support the hypothesis that cyanotoxin exposure may increase ALS risk.

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.

Incidence of multiple sclerosis in the province of Catania. A geo-epidemiological study

BACKGROUND

An increasing incidence of MS in the city of Catania was reported during 1975-2004, with a higher incidence along the south-eastern flank of the Mt.Etna. We evaluated the incidence of MS in the entire province of Catania during 2005-2015 and the spatial distribution of MS-cases using a cluster analysis.

METHODS

Patients were considered as incident MS-cases if they fulfilled the revised McDonald criteria for MS during 2005-2015 and were residents in the province of Catania at the time of disease onset. Cluster analysis was performed using both LISA and Kulldorff's spatial scan statistic. Residence address at disease onset was considered for each case. Communalities were assessed considering the centroid of their inhabited area.

RESULTS

A total of 973 MS-cases were identified. Mean annual incidence risk was 8.2/100,000 person-years (95%CI 7.7-8.7), significantly higher among women (10.5/100,000 versus 5.7/100,000). LISA identified a spatial aggregation of MS-cases in the eastern side of the province of Catania and Kulldorff's statistics confirmed the existence of a statistically significant spatial cluster in this area (SIR 1.23,95%CI 1.08-1.23, p-value 0.04).

CONCLUSIONS

Our study confirms a high incidence of MS in the province of Catania and the presence of a spatial cluster along the eastern side of the province. This area is considered the most exposed to volcanogenic ashes due to the prevailing westerly to north-westerly trade winds. Even if such distribution could be related with a greater exposure to volcanogenic metals, further studies are needed to explore possible alternative hypotheses.

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.

Fungal Neurotoxins and Sporadic Amyotrophic Lateral Sclerosis

We review several lines of evidence that point to a potential fungal origin of sporadic amyotrophic lateral sclerosis (ALS). ALS is the most common form of motor neuron disease (MND) in adults. It is a progressive and fatal disease. Approximately 90% cases of ALS are sporadic, and 5-10% are due to genetic mutations (familial). About 25 genes implicated in familial ALS have been identified so far, including SOD1 and TARDBP, the gene encoding 43 kDa transactive response (TAR) DNA-binding protein (TDP-43). Despite intensive research over many decades, the aetiology of sporadic ALS is still unknown. An environmental cause, including grass or soil-associated fungal infections, is suggested from a range of widely diverse lines of evidence. Clusters of ALS have been reported in soccer players, natives of Guam and farmers. Grass-associated fungi are known to produce a range of neurotoxins and, in symbiotic associations, high levels of fungal SOD1. Exposure of neurons to fungal neurotoxins elicits a significant increase in glutamate production. High levels of glutamate stimulate TDP-43 translocation and modification, providing a link between fungal infection and one of the molecular and histologic hallmarks of sporadic ALS. A recent study provided evidence of a variety of fungi in the cerebrospinal fluid and brain tissue of ALS patients. This review provides a rational explanation for this observation. If a fungal infection could be confirmed as a potential cause of ALS, this could provide a straightforward treatment strategy for this fatal and incurable disease.

The increasing importance of environmental conditions in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons (MNs). Although a small percentage of ALS has a familial origin, the vast majority of cases are sporadic in which genetic factors and environment interact with each other leading to disease onset in genetically predisposed individuals. In the current model of the disease, each individual has a determined genetic load, some degree of cell degeneration related to age and several risky environmental exposures. In this scenario, MN degeneration would occur when the sum of these factors reach a certain threshold. To date, an extensive list of environmental factors has been associated to ALS, including different categories, such as exposure to heavy metals and other toxicants, cyanotoxins or infectious agents. In addition, in recent years, lifestyle and other demographic parameters are gaining relevance in the genesis of the disease. Among them, physical activity, nutrition, body mass index, cardiovascular risk factors, autoimmune diseases and cancer are some of the conditions which have been related to the disease. In this review, we will discuss the potential mechanisms of environmental conditions in motor neuron degeneration. Understanding the role of each one of these factors as well as their interactions appears as a crucial step in order to develop new preventive, diagnostic and therapeutic approaches for ALS patients.

Spatial epidemiology of amyotrophic lateral sclerosis in Piedmont and Aosta Valley, Italy: a population-based cluster analysis

BACKGROUND AND PURPOSE

The analysis of the spatial distribution of cases could give important cues on putative environmental causes of a disease. Our aim was to perform a spatial analysis of an amyotrophic lateral sclerosis (ALS) cohort from the Piedmont and Aosta Valley ALS register (PARALS) over a 20-year period.

METHODS

The address at the moment of diagnosis was considered for each ALS case. Municipalities' and census divisions' resident populations during the 1995-2014 period were obtained. A cluster analysis was performed adopting both Moran's index and the Kulldorff spatial scan statistic.

RESULTS

A total of 2702 ALS patients were identified. An address was retrieved for 2671 (99%) patients. Moran's index was -0.01 (P value 0.83), thus revealing no clusters. SaTScan identified no statistically significant clusters. When census divisions were considered, Moran's index was 0.13 (P value 0.45); SaTScan revealed one statistically significant small cluster in the province of Alessandria. Here, 0.0099 cases were expected and three cases were observed (relative risk 304.60; 95% confidence interval 109.83-845.88, P value 0.03).

DISCUSSION

Our study showed a substantial homogeneous distribution of ALS cases in Piedmont and Aosta Valley. The population-based setting and the adoption of proper statistical analyses strengthen the validity of our results. Such a finding further suggests the involvement of multiple environmental and genetic factors in ALS pathogenesis.

Metals and neurodegenerative diseases. A systematic review

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical presentation such as Amyotrophic Lateral Sclerosis (ALS), Alzheimer Disease (AD) and Parkinson's disease (PD). Genetic mutations have a known causative role, but the majority of cases are likely to be probably caused by a complex gene-environment interaction. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies and it is likely that each metal could be toxic through specific pathways. The possible pathogenic role of different metals has been supported by some epidemiological evidences coming from occupational and ecological studies. In order to assess the possible association between metals and neurodegenerative disorders, several case-control studies have also been carried out evaluating the metals concentration in different biological specimens such as blood/serum/plasma, cerebrospinal fluid (CSF), nail and hair, often reporting conflicting results. This review provides an overview of our current knowledge on the possible association between metals and ALS, AD and PD as main neurodegenerative disorders.

Pesticide exposure assessed through agricultural crop proximity and risk of amyotrophic lateral sclerosis

BACKGROUND

Epidemiologic studies have raised the possibility that some pesticide compounds induce the neurodegenerative disease amyotrophic lateral sclerosis (ALS), though the available evidence is not entirely consistent.

METHODS

We conducted a population-based case-control study in two Italian populations to assess the extent to which residence in the vicinity of agricultural crops associated with the application of neurotoxic pesticides is a risk factor for ALS, using crop acreage in proximity to the residence as an index of exposure.

RESULTS

Based on 703 cases and 2737 controls, we computed an ALS odds ratio of 0.92 (95% confidence interval 0.78-1.09) for those in proximity to agricultural land. Results were not substantially different when using alternative exposure categories or when analyzing specific crop types, with the exception of a higher risk related to exposure to citrus orchards and olive groves in Southern Italy, though based on few exposed subjects (N = 89 and 8, respectively). There was little evidence of any dose-response relation between crop proximity and ALS risk, and using long-term residence instead of current residence did not substantially change our estimates.

CONCLUSIONS

Though our index of exposure is indirect and subject to considerable misclassification, our results offer little support for the hypothesis that neurotoxic pesticide exposure increases ALS risk.

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.

Blood trace metals in a sporadic amyotrophic lateral sclerosis geographical cluster

Amyotrophic lateral sclerosis (ALS) is a fatal disorder with unknown etiology, in which genetic and environmental factors interplay to determine the onset and the course of the disease. Exposure to toxic metals has been proposed to be involved in the etiology of the disease either through a direct damage or by promoting oxidative stress. In this study we evaluated the concentration of a panel of metals in serum and whole blood of a small group of sporadic patients, all living in a defined geographical area, for which acid mine drainage has been reported. ALS prevalence in this area is higher than in the rest of Italy. Results were analyzed with software based on artificial neural networks. High concentrations of metals (in particular Se, Mn and Al) were associated with the disease group. Arsenic serum concentration resulted lower in ALS patients, but it positively correlated with disease duration. Comet assay was performed to evaluate endogenous DNA damage that resulted not different between patients and controls. Up to now only few studies considered geographically well-defined clusters of ALS patients. Common geographical origin among patients and controls gave us the chance to perform metallomic investigations under comparable conditions of environmental exposure. Elaboration of these data with software based on machine learning processes has the potential to be extremely useful to gain a comprehensive view of the complex interactions eventually leading to disease, even in a small number of subjects.

Motor neuron disease mortality and lifetime petrol lead exposure: Evidence from national age-specific and state-level age-standardized death rates in Australia

BACKGROUND

The age standardized death rate from motor neuron disease (MND) for persons 40-84 years of age in the Australian States of New South Wales, Victoria, and Queensland increased dramatically from 1958 to 2013. Nationally, age-specific MND death rates also increased over this time period, but the rate of the rise varied considerably by age-group. The historic use of lead (Pb) additives in Australian petrol is a candidate explanation for these trends in MND mortality (International Classification of Disease (ICD)-10 G12.2).

METHODS

Leveraging temporal and spatial variation in petrol lead exposure risk resulting from the slow rise and rapid phase-out of lead as a constituent in gasoline in Australia, we analyze relationships between (1) national age-specific MND death rates in Australia and age-specific lifetime petrol lead exposure, (2) annual between-age dispersions in age-specific MND death rates and age-specific lifetime petrol lead exposure; and (3) state-level age-standardized MND death rates as a function of age-weighted lifetime petrol lead exposure.

RESULTS

Other things held equal, we find that a one percent increase in lifetime petrol lead exposure increases the MND death rate by about one-third of one percent in both national age-specific and state-level age-standardized models of MND mortality. Lending support to the supposition that lead exposure is a driver of MND mortality risk, we find that the annual between-age group standard deviation in age-specific MND death rates is strongly correlated with the between-age standard deviation in age-specific lifetime petrol lead exposure.

CONCLUSION

Legacy petrol lead emissions are associated with age-specific MND death rates as well as state-level age-standardized MND death rates in Australia. Results indicate that we are approaching peak lead exposure-attributable MND mortality.