Effect modification of the association between total cigarette smoking and ALS risk by intensity, duration and time-since-quitting: Euro-MOTOR

Exploring the impact of circular RNA on ALS progression: A systematic review

Amyotrophic lateral sclerosis is a neurodegenerative disease that damages motor neurons and causes gradual muscular weakening and paralysis. Although studies have linked a number of genetic and environmental factors to ALS, the specific causes and mechanisms of the disease are still unclear. The pivotal role of circular RNA in the pathogenesis of ALS is a newly emerging area of research. The term "circular RNA" describes a particular class of RNA molecule that, in contrast to most RNA molecules, has a closed-loop structure. According to recent research, circular RNA might be essential for the development and progression of ALS. It has been discovered that these circular RNAs support important cellular functions related to ALS, including protein turnover, mitochondrial function, RNA processing, and cellular transport. Gaining knowledge about the precise roles and processes of circular RNA in the development of ALS could assist in understanding the pathophysiology of the disease and possibly pave the way for the development of targeted therapies. However, the understanding of circular RNA in ALS is still limited, and more research is needed to fully elucidate its role. In order to gain a comprehensive understanding of the role of circRNAs in ALS, it is imperative to delve into the various mechanisms through which circRNAs may contribute to the development and progression of the disease. Examining the current status of circRNA research in ALS and offering insights into their potential as therapeutic targets and diagnostic markers are the primary objectives of this review.

Lifestyle and medical conditions in relation to ALS risk and progression-an introduction to the Swedish ALSrisc Study

BACKGROUND

This study was an introduction to the Swedish ALSrisc Study and explored the association of lifestyle and medical conditions, with risk and progression of amyotrophic lateral sclerosis (ALS).

METHODS

We included 265 newly diagnosed ALS patients during 2016-2022 in Stockholm and 207 ALS-free siblings and partners of the patients as controls. Information on body mass index (BMI), smoking, and history of head injuries, diabetes mellitus, hypercholesterolemia, and hypertension was obtained through the Euro-MOTOR questionnaire at recruitment. Patients were followed from diagnosis until death, invasive ventilation, or November 30, 2022.

RESULTS

Higher BMI at recruitment was associated with lower risk for ALS (OR 0.89, 95%CI 0.83-0.95), especially among those diagnosed after 65 years. One unit increase in the average BMI during the 3 decades before diagnosis was associated with a lower risk for ALS (OR 0.94, 95%CI 0.89-0.99). Diabetes was associated with lower risk of ALS (OR 0.38, 95%CI 0.16-0.90), while hypercholesterolemia was associated with higher risk of ALS (OR 2.10, 95%CI 1.13-3.90). Higher BMI at diagnosis was associated with lower risk of death (HR 0.91, 95%CI 0.84-0.98), while the highest level of smoking exposure (in pack-years) (HR 1.90, 95%CI 1.20-3.00), hypercholesterolemia (HR 1.84, 95%CI 1.06-3.19), and hypertension (HR 1.76, 95%CI 1.03-3.01) were associated with higher risk of death, following ALS diagnosis.

CONCLUSIONS

Higher BMI and diabetes were associated with lower risk of ALS. Higher BMI was associated with lower risk of death, whereas smoking (especially in high pack-years), hypercholesterolemia, and hypertension were associated with higher risk of death after ALS diagnosis.

Air pollution exposure and mortality from neurodegenerative diseases in the Netherlands: A population-based cohort study

BACKGROUND

Long-term exposure to ambient air pollution has been linked with all-cause mortality and cardiovascular and respiratory diseases. Suggestive associations between ambient air pollutants and neurodegeneration have also been reported, but due to the small effect and relatively rare outcomes evidence is yet inconclusive. Our aim was to investigate the associations between long-term air pollution exposure and mortality from neurodegenerative diseases.

METHODS

A Dutch national cohort of 10.8 million adults aged ≥30 years was followed from 2013 until 2019. Annual average concentrations of air pollutants (ultra-fine particles (UFP), nitrogen dioxide (NO2), fine particles (PM2.5 and PM10) and elemental carbon (EC)) were estimated at the home address at baseline, using land-use regression models. The outcome variables were mortality due to amyotrophic lateral sclerosis (ALS), Parkinson's disease, non-vascular dementia, Alzheimer's disease, and multiple sclerosis (MS). Hazard ratios (HR) were estimated using Cox models, adjusting for individual and area-level socio-economic status covariates.

RESULTS

We had a follow-up of 71 million person-years. The adjusted HRs for non-vascular dementia were significantly increased for NO2 (1.03; 95% confidence interval (CI) 1.02-1.05) and PM2.5 (1.02; 95%CI 1.01-1.03) per interquartile range (IQR; 6.52 and 1.47 μg/m3, respectively). The association with PM2.5 was also positive for ALS (1.02; 95%CI 0.97-1.07). These associations remained positive in sensitivity analyses and two-pollutant models. UFP was not associated with any outcome. No association with air pollution was found for Parkinson's disease and MS. Inverse associations were found for Alzheimer's disease.

CONCLUSION

Our findings, using a cohort of more than 10 million people, provide further support for associations between long-term exposure to air pollutants (PM2.5 and particularly NO2) and mortality of non-vascular dementia. No associations were found for Parkinson and MS and an inverse association was observed for Alzheimer's disease.

Serum heat shock protein concentrations are not associated with amyotrophic lateral sclerosis risk or survival in three European populations

Introduction: Serum heat shock protein (HSP) concentrations have been reported as potential biomarkers for amyotrophic lateral sclerosis (ALS). Here, we investigate the role of serum HSP70, HSP90, and DNAJC7 as biomarkers for ALS. Methods: Serum samples were collected from ALS patients and volunteer controls from three different clinical cohorts (in Germany, Ireland, and Italy). Serum HSP concentrations were determined using enzyme-linked immunosorbent assay. Descriptive statistics, generalized logistic regression, and Cox proportional hazards models were used to model associations between log serum HSP concentrations and ALS risk. Results: In total, 251 ALS patients and 184 healthy volunteers were included. Logistic regression models failed to find associations between ALS risk and log serum concentration of HSP70 (OR 0.43, 95% CI: 0.10-1.78, p = 0.242), HSP90 (OR 0.95, 95% CI: 0.39-2.37, p = 0.904), or DNAJC7 (OR 1.55, 95% CI: 0.90-2.68, p = 0.118). Survival of ALS patients was not associated with log serum concentration of HSP HSP70 (HR1.06, 95% CI: 0.36-3.14, p = 0.916), HSP90 (HR 1.17, 95% CI: 0.67-2.02, p = 0.584), or DNAJC7 (HR 0.83, 95% CI: 0.57-1.21, p = 0.337). Discussion: We did not replicate previous findings that serum HSP70 and HSP90 concentrations were associated with risk of ALS. DNAJC7 was not associated with ALS risk, and there were no obvious longitudinal patterns in log serum concentrations of HSP70, HSP90, or DNAJC7. In addition, serum HSP concentrations were not associated with ALS survival.

Role of the Exposome in Neurodegenerative Disease: Recent Insights and Future Directions

Neurodegenerative diseases are increasing in prevalence and place a significant burden on society. The causes are multifactorial and complex, and increasing evidence suggests a dynamic interplay between genes and the environment, emphasizing the importance of identifying and understanding the role of lifelong exposures, known as the exposome, on the nervous system. This review provides an overview of recent advances toward defining neurodegenerative disease exposomes, focusing on Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We present the current state of the field based on emerging data, elaborate on key themes and potential mechanisms, and conclude with limitations and future directions. ANN NEUROL 2024;95:635-652.

The amyotrophic lateral sclerosis exposome: recent advances and future directions

Amyotrophic lateral sclerosis (ALS) is a fatal disease of motor neuron degeneration with typical survival of only 2-5 years from diagnosis. The causes of ALS are multifactorial: known genetic mutations account for only around 70% of cases of familial ALS and 15% of sporadic cases, and heritability estimates range from 8% to 61%, indicating additional causes beyond genetics. Consequently, interest has grown in environmental contributions to ALS risk and progression. The gene-time-environment hypothesis posits that ALS onset occurs through an interaction of genes with environmental exposures during ageing. An alternative hypothesis, the multistep model of ALS, suggests that several hits, at least some of which could be environmental, are required to trigger disease onset, even in the presence of highly penetrant ALS-associated mutations. Studies have sought to characterize the ALS exposome - the lifetime accumulation of environmental exposures that increase disease risk and affect progression. Identifying the full scope of environmental toxicants that enhance ALS risk raises the prospect of preventing disease by eliminating or mitigating exposures. In this Review, we summarize the evidence for an ALS exposome, discussing the strengths and limitations of epidemiological studies that have identified contributions from various sources. We also consider potential mechanisms of exposure-mediated toxicity and suggest future directions for ALS exposome research.

Gene-Environment Interactions in Repeat Expansion Diseases: Mechanisms of Environmentally Induced Repeat Instability

Short tandem repeats (STRs) are units of 1-6 base pairs that occur in tandem repetition to form a repeat tract. STRs exhibit repeat instability, which generates expansions or contractions of the repeat tract. Over 50 diseases, primarily affecting the central nervous system and muscles, are characterized by repeat instability. Longer repeat tracts are typically associated with earlier age of onset and increased disease severity. Environmental exposures are suspected to play a role in the pathogenesis of repeat expansion diseases. Here, we review the current knowledge of mechanisms of environmentally induced repeat instability in repeat expansion diseases. The current evidence demonstrates that environmental factors modulate repeat instability via DNA damage and induction of DNA repair pathways, with distinct mechanisms for repeat expansion and contraction. Of particular note, oxidative stress is a key mediator of environmentally induced repeat instability. The preliminary evidence suggests epigenetic modifications as potential mediators of environmentally induced repeat instability. Future research incorporating an array of environmental exposures, new human cohorts, and improved model systems, with a continued focus on cell-types, tissues, and critical windows, will aid in identifying mechanisms of environmentally induced repeat instability. Identifying environmental modulators of repeat instability and their mechanisms of action will inform preventions, therapies, and public health measures.

1,2-Dehydropyrrolizidine Alkaloids: Their Potential as a Dietary Cause of Sporadic Motor Neuron Diseases

Sporadic motor neuron diseases (MNDs), such as amyotrophic lateral sclerosis (ALS), can be caused by spontaneous genetic mutations. However, many sporadic cases of ALS and other debilitating neurodegenerative diseases (NDDs) are believed to be caused by environmental factors, subject to considerable debate and requiring intensive research. A common pathology associated with MND development involves progressive mitochondrial dysfunction and oxidative stress in motor neurons and glial cells of the central nervous system (CNS), leading to apoptosis. Consequent degeneration of skeletal and respiratory muscle cells can lead to death from respiratory failure. A significant number of MND cases present with cancers and liver and lung pathology. This Perspective explores the possibility that MNDs could be caused by intermittent, low-level dietary exposure to 1,2-dehydropyrrolizidine alkaloids (1,2-dehydroPAs) that are increasingly recognized as contaminants of many foods consumed throughout the world. Nontoxic, per se, 1,2-dehydroPAs are metabolized, by particular cytochrome P450 (CYP450) isoforms, to 6,7-dihydropyrrolizines that react with nucleophilic groups (-NH, -SH, -OH) on DNA, proteins, and other vital biochemicals, such as glutathione. Many factors, including aging, gender, smoking, and alcohol consumption, influence CYP450 isoform activity in a range of tissues, including glial cells and neurons of the CNS. Activation of 1,2-dehydroPAs in CNS cells can be expected to cause gene mutations and oxidative stress, potentially leading to the development of MNDs and other NDDs. While relatively high dietary exposure to 1,2-dehydroPAs causes hepatic sinusoidal obstruction syndrome, pulmonary venoocclusive disease, neurotoxicity, and diverse cancers, this Perspective suggests that, at current intermittent, low levels of dietary exposure, neurotoxicity could become the primary pathology that develops over time in susceptible individuals, along with a tendency for some of them to also display liver and lung pathology and diverse cancers co-occurring with some MND/NDD cases. Targeted research is recommended to investigate this proposal.

Incidence of and Mortality From Amyotrophic Lateral Sclerosis in National Football League Athletes

Importance

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease; understanding ALS risk factors is a critical public health issue.

Objectives

To evaluate the incidence of and mortality from ALS in National Football League (NFL) athletes and to describe characteristics associated with ALS within this cohort.

Design, Setting, and Participants

This population-based cohort study included all 19 423 NFL athletes who debuted between 1960 and 2019 and played 1 or more professional game. It was conducted between October 3, 2020, and July 19, 2021.

Exposure

Participation in the NFL, including playing 1 or more professional games.

Main Outcomes and Measures

Cases of ALS and death information were identified based on public records from NFL statistics aggregators, news reports, obituaries, and National Death Index results. The standardized incidence ratio and the standardized mortality ratio were calculated based on data acquired from surveillance studies of ALS accounting for age, sex, and race. Secondary analyses examined the association of body mass index, NFL career duration, race, birth location, and markers of fame, using a nested case-control design, matching athletes with ALS to athletes without ALS, by NFL debut year.

Results

A total of 19 423 male former and current NFL players (age range, 23-78 years) were included in this cohort study and were followed up for a cumulative 493 168 years (mean [SD] follow-up, 30.6 [13.7] years). Thirty-eight players received a diagnosis of ALS, and 28 died during the study time frame, representing a significantly higher incidence of ALS diagnosis (standardized incidence ratio, 3.59; 95% CI, 2.58-4.93) and mortality (standardized mortality ratio, 3.94; 95% CI, 2.62-5.69) among NFL players compared with the US male population, adjusting for age and race. Among NFL athletes, nested-case-control analyses found that those who received a diagnosis of ALS had significantly longer careers (mean [SD] duration, 7.0 [3.9] years) than athletes without ALS (mean [SD] duration, 4.5 [3.6] years; odds ratio, 1.2; 95% CI, 1.1-1.3). There were no differences in ALS status based on proxies of NFL fame, body mass index, position played, birth location, or race.

Conclusions and Relevance

The age-, sex-, and race-adjusted incidence of and mortality from ALS among all NFL players who debuted between 1960 and 2019 were nearly 4 times as high as those of the general population. Athletes with a diagnosis of ALS had longer NFL careers than those without ALS, suggesting an association between NFL duration of play and ALS. The identification of these risk factors for ALS helps to inform the study of pathophysiological mechanisms responsible for this fatal neurodegenerative disease.

Coffee and Tea Consumption Impact on Amyotrophic Lateral Sclerosis Progression: A Multicenter Cross-Sectional Study

Background/objectives: Amyotrophic lateral sclerosis (ALS) is a devastating and still untreatable motor neuron disease. The causes of ALS are unknown, but nutritional factors may impact the rate of disease progression. We aimed to ascertain the influence of coffee and tea consumption on ALS progression rate.

Subjects/methods: In this multicenter cross-sectional study, we recruited 241 patients, 96 females, and 145 males; the mean age at onset was 59.9 ± 11.8 years. According to El Escorial criteria, 74 were definite ALS, 77 probable, 55 possible, and 35 suspected; 187 patients had spinal onset and 54 bulbar. Patients were categorized into three groups, according to their ΔFS (derived from ALS Functional Rating Scale-Revised score and disease duration from onset): slow (81), intermediate (80), and fast progressors (80).

Results: Current coffee consumers were 179 (74.3%), 34 (14.1%) were non-consumers, and 22 (9.1%) were former consumers, whereas six (2.5%) consumed decaffeinated coffee only. The log-ΔFS was weakly correlated with the duration of coffee consumption (p = 0.034), but not with the number of cup-years, or the intensity of coffee consumption (cups/day). Current tea consumers were 101 (41.9%), 6 (2.5%) were former consumers, and 134 (55.6%) were non-consumers. Among current and former consumers, 27 (25.2%) consumed only green tea, 51 (47.7%) only black tea, and 29 (27.1%) both. The log-ΔFS was weakly correlated only with the consumption duration of black tea (p = 0.028) but not with the number of cup-years.

Conclusions: Our study does not support the hypothesis that coffee or tea consumption is associated with the ALS progression rate.

Associations between lifestyle and amyotrophic lateral sclerosis stratified by C9orf72 genotype: a longitudinal, population-based, case-control study

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is considered to be caused by both genetic and environmental factors. The causal cascade is, however, not known. We aimed to assess lifestyle during the presymptomatic phase of ALS, stratified by C9orf72 mutation, and examine evidence supporting causality of lifestyle factors.

METHODS

This study was a longitudinal, population-based, case-control study that used data from the Prospective ALS study the Netherlands. We included patients with a C9orf72 mutation (C9+ group), patients without a C9orf72 mutation (C9- group), and controls. Patients fulfilled the revised El Escorial criteria and were recruited through neurologists and rehabilitation physicians in the Netherlands as well as the Dutch Neuromuscular Patient Association and ALS Centrum website. 1322 population-based controls, matched for age and sex, were enrolled via the patients' general practitioners. Blood relatives or spouses of patients were not eligible as controls. We studied the relationship between ALS risk and smoking, alcohol, physical activity, body-mass index (BMI), and energy intake by the use of structured questionnaires. Smoking, physical activity, and BMI were longitudinally assessed up to 50 years before onset (defined as the period before onset of muscle weakness or bulbar symptoms for cases, or age at completing the questionnaire for controls). We calculated posterior probabilities (P(θ|x)) for causal effects of smoking, alcohol, and BMI, using Bayesian instrumental variable analyses.

FINDINGS

Between Jan 1, 2006 and Jan 27, 2016, we included 143 patients in the C9+ group, 1322 patients in the C9- group, and 1322 controls. Compared with controls, cigarette pack-years (C9+ group mean difference from control 3·15, 95% CI 0·36 to 5·93, p=0·027; C9- group 3·20, 2·02 to 4·39, p<0·0001) and daily energy intake at symptom onset (C9+ group 712 kJ, 95% CI 212 to 1213, p=0·0053; C9- group 497, 295 to 700, p<0·0001) were higher in the C9+ and C9- groups, whereas current BMI (C9+ group -2·01 kg/m², 95% CI -2·73 to -1·29, p<0·0001; C9- group -1·35, -1·64 to -1·06, p<0·0001) and lifetime alcohol consumption (C9+ group -5388 units, 95% CI -9113 to -1663, p=0·0046; C9- group -2185, -3748 to -622, p=0·0062) were lower in the C9+ and C9- groups. Median BMI during the presymptomatic phase for the C9+ group was lower (-0·69 kg/m², 95% CI -1·24 to -0·13, p=0·015) and physical activity was similar (-348 metabolic equivalent of task [MET], 95% CI -966 to 270, p=0·27) to controls, whereas both the median BMI during the presymptomatic phase (0·27 kg/m², 95% CI 0·04 to 0·50, p=0·022) and physical activity (585 MET, 291 to 878, p=0·0001) were higher in the C9- group than controls. Longitudinal analyses showed more cigarette pack-years in the C9- (starting 47 years pre-onset) and C9+ (starting 24 years pre-onset) groups, and higher physical activity over time in the C9- group (starting >30 years pre-onset). BMI of the C9+ group increased more slowly and was significantly lower (starting at 36 years pre-onset) than in controls, whereas the BMI of the C9- group was higher than controls (23-49 years pre-onset, becoming lower 10 years pre-onset). Instrumental variable analyses supported causal effects of alcohol consumption (P(θ|x)=0·9347) and smoking (P(θ|x)=0·9859) on ALS in the C9- group. We found evidence supporting a causal effect of increased BMI at younger age (mean 33·8 years, SD 11·7) in the C9- group (P[θ|x]=0·9272), but not at older ages.

INTERPRETATION

Lifestyle during the presymptomatic phase differs between patients with ALS and controls decades before onset, depends on C9- status, and is probably part of the presymptomatic causal cascade. Identification of modifiable disease-causing lifestyle factors offers opportunities to lower risk of developing neurodegenerative disease.

FUNDING

Netherlands ALS Foundation.

Pathophysiological Correlation between Cigarette Smoking and Amyotrophic Lateral Sclerosis

Cigarette smoke (CS) has been consistently demonstrated to be an environmental risk factor for amyotrophic lateral sclerosis (ALS), although the molecular pathogenic mechanisms involved are yet to be elucidated. Here, we propose different mechanisms by which CS exposure can cause sporadic ALS pathogenesis. Oxidative stress and neuroinflammation are widely implicated in ALS pathogenesis, with blood–spinal cord barrier disruption also recognised to be involved in the disease process. In addition, immunometabolic, epigenetic and microbiome alterations have been implicated in ALS recently. Identification of the underlying pathophysiological mechanisms that underpin CS-associated ALS will drive future research to be conducted into new targets for treatment.

The Impact of Lifetime Alcohol and Cigarette Smoking Loads on Amyotrophic Lateral Sclerosis Progression: A Cross-Sectional Study

Background—Amyotrophic lateral sclerosis (ALS) is a devastating and untreatable motor neuron disease; smoking and alcohol drinking may impact its progression rate. Objective—To ascertain the influence of smoking and alcohol consumption on ALS progression rates. Methods—Cross-sectional multicenter study, including 241 consecutive patients (145 males); mean age at onset was 59.9 ± 11.8 years. Cigarette smoking and alcohol consumption data were collected at recruitment through a validated questionnaire. Patients were categorized into three groups according to ΔFS (derived from the ALS Functional Rating Scale-Revised and disease duration from onset): slow (n = 81), intermediate (80), and fast progressors (80). Results—Current smokers accounted for 44 (18.3%) of the participants, former smokers accounted for 10 (4.1%), and non-smokers accounted for 187 (77.6%). The age of ALS onset was lower in current smokers than non-smokers, and the ΔFS was slightly, although not significantly, higher for smokers of >14 cigarettes/day. Current alcohol drinkers accounted for 147 (61.0%) of the participants, former drinkers accounted for 5 (2.1%), and non-drinkers accounted for 89 (36.9%). The log(ΔFS) was weakly correlated only with the duration of alcohol consumption (p = 0.028), but not with the mean number of drinks/day or the drink-years. Conclusions: This cross-sectional multicenter study suggested a possible minor role for smoking in worsening disease progression. A possible interaction with alcohol drinking was suggested.

Genetic analysis of ALS cases in the isolated island population of Malta

Genetic isolates are compelling tools for mapping genes of inherited disorders. The archipelago of Malta, a sovereign microstate in the south of Europe is home to a geographically and culturally isolated population. Here, we investigate the epidemiology and genetic profile of Maltese patients with amyotrophic lateral sclerosis (ALS), identified throughout a 2-year window. Cases were largely male (66.7%) with a predominant spinal onset of symptoms (70.8%). Disease onset occurred around mid-age (median age: 64 years, men; 59.5 years, female); 12.5% had familial ALS (fALS). Annual incidence rate was 2.48 (95% CI 1.59–3.68) per 100,000 person-years. Male-to-female incidence ratio was 1.93:1. Prevalence was 3.44 (95% CI 2.01–5.52) cases per 100,000 inhabitants on 31^st December 2018. Whole-genome sequencing allowed us to determine rare DNA variants that change the protein-coding sequence of ALS-associated genes. Interestingly, the Maltese ALS patient cohort was found to be negative for deleterious variants in C9orf72, SOD1, TARDBP or FUS genes, which are the most commonly mutated ALS genes globally. Nonetheless, ALS-associated repeat expansions were identified in ATXN2 and NIPA1. Variants predicted to be damaging were also detected in ALS2, DAO, DCTN1, ERBB4, SETX, SCFD1 and SPG11. A total of 40% of patients with sporadic ALS had a rare and deleterious variant or repeat expansion in an ALS-associated gene, whilst the genetic cause of two thirds of fALS cases could not be pinpointed to known ALS genes or risk loci. This warrants further studies to elucidate novel genes that cause ALS in this unique population isolate.

Blood Metal Levels and Amyotrophic Lateral Sclerosis Risk: A Prospective Cohort

OBJECTIVE

Metals have been suggested as a risk factor for amyotrophic lateral sclerosis (ALS), but only retrospective studies are available to date. We compared metal levels in prospectively collected blood samples from ALS patients and controls, to explore whether metals are associated with ALS mortality.

METHODS

A nested ALS case-control study was conducted within the prospective EPIC (European Prospective Investigation into Cancer and Nutrition) cohort. Cases were identified through death certificates. We analyzed metal levels in erythrocyte samples obtained at recruitment, as a biomarker for metal exposure from any source. Arsenic, cadmium, copper, lead, manganese, mercury, selenium, and zinc concentrations were measured by inductively coupled plasma-mass spectrometry. To estimate ALS risk, we applied conditional logistic regression models.

RESULTS

The study population comprised 107 cases (65% female) and 319 controls matched for age, sex, and study center. Median time between blood collection and ALS death was 8 years (range = 1-15). Comparing the highest with the lowest tertile, cadmium (odds ratio [OR] = 2.04, 95% confidence interval [CI] = 1.08-3.87) and lead (OR = 1.89, 95% CI = 0.97-3.67) concentrations suggest associations with increased ALS risk. Zinc was associated with a decreased risk (OR = 0.50, 95% CI = 0.27-0.94). Associations for cadmium and lead remained when limiting analyses to noncurrent smokers.

INTERPRETATION

This is the first study to compare metal levels before disease onset, minimizing reverse causation. The observed associations suggest that cadmium, lead, and zinc may play a role in ALS etiology. Cadmium and lead possibly act as intermediates on the pathway from smoking to ALS. ANN NEUROL 20209999:n/a-n/a.

Cardiovascular comorbidities in amyotrophic lateral sclerosis

BACKGROUND

The role of cardiovascular risk factors in amyotrophic lateral sclerosis (ALS) is controversial. A favourable profile has been found in ALS patients, but previous studies have not specifically considered the profile in different disease phenotypes.

METHODS

Demographic data, smoking habits, lifetime exercise, and medical history including diabetes mellitus, arterial hypertension, hypercholesterolemia, hypertriglyceridemia, stroke, and cardiac events, were analysed in ALS patients and in controls with other neurological disorders, utilising a standardized questionnaire applied by the same neurologist. In ALS patients the results were analysed according to their different phenotypes. Univariate analyses and multinomial logistic models were applied to estimate the odds ratios (ORs) and confidence intervals (CIs) for covariates, to test potential modifiers and their effects.

RESULTS

500 consecutively assessed adult ALS patients (mean age 65.6, 47% women, and 136 bulbar-onset) and 327 age and gender-matched controls were studied. Patients with spinal-onset ALS took more exercise (p = 0.012), reported less hypertension (p = 0.002) and had fewer cardiac events (p = 0.012). Multinomial regression analysis showed that men without hypertension have a higher risk of having spinal-onset ALS (p < 0.001) while female with hypertension have a higher risk of having bulbar-onset ALS (p = 0.033).

CONCLUSIONS

Risk-factors in ALS can be influenced by gender and phenotype. This study suggests that men with spinal ALS are healthier, exercise more and have lower rate of hypertension, but females with bulbar-onset ALS are more prone to hypertension. The complex interplay between exercise, diet and comorbidities with ALS phenotype requires further investigation.

Multicentre, prospective registry study of amyotrophic lateral sclerosis in mainland China (CHALSR): study protocol

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a representative rare disease characterised by progressive, fatal motor neuron degeneration. Due to the unknown aetiology and variability of the phenotypes, there are no accurate reports concerning the epidemiology or clinical characteristics of the disease. The low prevalence, as previously reported, makes it difficult to carry out studies with large samples. The aim of this study was to explore the natural history and clinical features of ALS in mainland China through a multicentre, prospective cohort study. The findings will both offer a better understanding of ALS and also support the development of a model to study other rare diseases.

METHODS AND ANALYSIS

Patients from 88 representative hospitals in different parts of mainland China will be recruited through a specially designed online data system (http://www.chalsr.net/). We aim to recruit 4752 ALS patients over a 3-year period. Baseline data will be recorded, and follow-up data will be collected every 3 months. The primary outcome is effective survival. Overall survival and indices of disease progression will be measured as the secondary outcomes.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the ethics committee of Peking University Third Hospital (M2019388). Informed written consent will be obtained from each participant. Dissemination of the study protocol and data will take place primarily through a specially designed online data system (http://www.chalsr.net/). The collective results of the study will be published in peer-reviewed journals and shared in scientific presentations.

TRIAL REGISTRATION NUMBER

NCT04328675.

Relationship between smoking and ALS: Mendelian randomisation interrogation of causality

OBJECTIVE

Smoking has been widely studied as a susceptibility factor for amyotrophic lateral sclerosis (ALS), but results are conflicting and at risk of confounding bias. We used the results of recently published large genome-wide association studies and Mendelian randomisation methods to reduce confounding to assess the relationship between smoking and ALS.

METHODS

Two genome-wide association studies investigating lifetime smoking (n=463 003) and ever smoking (n=1 232 091) were identified and used to define instrumental variables for smoking. A genome-wide association study of ALS (20 806 cases; 59 804 controls) was used as the outcome for inverse variance weighted Mendelian randomisation, and four other Mendelian randomisation methods, to test whether smoking is causal for ALS. Analyses were bidirectional to assess reverse causality.

RESULTS

There was no strong evidence for a causal or reverse causal relationship between smoking and ALS. The results of Mendelian randomisation using the inverse variance weighted method were: lifetime smoking OR 0.94 (95% CI 0.74 to 1.19), p value 0.59; ever smoking OR 1.10 (95% CI 1 to 1.23), p value 0.05.

CONCLUSIONS

Using multiple methods, large sample sizes and sensitivity analyses, we find no evidence with Mendelian randomisation techniques that smoking causes ALS. Other smoking phenotypes, such as current smoking, may be suitable for future Mendelian randomisation studies.

Diet, Microbiota and Brain Health: Unraveling the Network Intersecting Metabolism and Neurodegeneration

Increasing evidence gives support for the idea that extra-neuronal factors may affect brain physiology and its predisposition to neurodegenerative diseases. Epidemiological and experimental studies show that nutrition and metabolic disorders such as obesity and type 2 diabetes increase the risk of Alzheimer's and Parkinson's diseases after midlife, while the relationship with amyotrophic lateral sclerosis is uncertain, but suggests a protective effect of features of metabolic syndrome. The microbiota has recently emerged as a novel factor engaging strong interactions with neurons and glia, deeply affecting their function and behavior in these diseases. In particular, recent evidence suggested that gut microbes are involved in the seeding of prion-like proteins and their spreading to the central nervous system. Here, we present a comprehensive review of the impact of metabolism, diet and microbiota in neurodegeneration, by affecting simultaneously several aspects of health regarding energy metabolism, immune system and neuronal function. Advancing technologies may allow researchers in the future to improve investigations in these fields, allowing the buildup of population-based preventive interventions and development of targeted therapeutics to halt progressive neurologic disability.

Role of Alcohol Drinking in Alzheimer's Disease, Parkinson's Disease, and Amyotrophic Lateral Sclerosis

Neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), increase as the population ages around the world. Environmental factors also play an important role in most cases. Alcohol consumption exists extensively and it acts as one of the environmental factors that promotes these neurodegenerative diseases. The brain is a major target for the actions of alcohol, and heavy alcohol consumption has long been associated with brain damage. Chronic alcohol intake leads to elevated glutamate-induced excitotoxicity, oxidative stress and permanent neuronal damage associated with malnutrition. The relationship and contributing mechanisms of alcohol with these three diseases are different. Epidemiological studies have reported a reduction in the prevalence of Alzheimer’s disease in individuals who drink low amounts of alcohol; low or moderate concentrations of ethanol protect against β-amyloid (Aβ) toxicity in hippocampal neurons; and excessive amounts of ethanol increase accumulation of Aβ and Tau phosphorylation. Alcohol has been suggested to be either protective of, or not associated with, PD. However, experimental animal studies indicate that chronic heavy alcohol consumption may have dopamine neurotoxic effects through the induction of Cytochrome P450 2E1 (CYP2E1) and an increase in the amount of α-Synuclein (αSYN) relevant to PD. The findings on the association between alcohol consumption and ALS are inconsistent; a recent population-based study suggests that alcohol drinking seems to not influence the risk of developing ALS. Additional research is needed to clarify the potential etiological involvement of alcohol intake in causing or resulting in major neurodegenerative diseases, which will eventually lead to potential therapeutics against these alcoholic neurodegenerative diseases.