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Amyotrophic lateral sclerosis (ALS) is a relatively rare but fatal neurodegenerative disease with the progressive loss of both upper and lower motor neurons. Although electromyography, imaging and multi-omics technologies have suggested numerous functional, structural, circulating and microbiota markers for ALS, no clinically validated markers have, as yet, been identified. Here we summarize the advances to characterize markers underlying ALS pathophysiology as well as their potential use in diagnosis, prognosis and therapy., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Experimental observations have suggested a role of infection in the etiology of neurodegenerative disease. In human studies, however, it is difficult to disentangle whether infection is a risk factor or rather a comorbidity or secondary event of neurodegenerative disease. To this end, we examined the risk of 3 most common neurodegenerative diseases in relation to previous inpatient or outpatient episodes of hospital-treated infections., Methods and Findings: We performed a nested case-control study based on several national registers in Sweden. Cases were individuals newly diagnosed with Alzheimer's disease (AD), Parkinson's disease (PD), or amyotrophic lateral sclerosis (ALS) during 1970 to 2016 in Sweden, identified from the National Patient Register. For each case, 5 controls individually matched to the case on sex and year of birth were randomly selected from the general population. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) with adjustment for potential confounders, including sex, year of birth, area of residence, educational attainment, family history of neurodegenerative disease, and Charlson comorbidity index. Infections experienced within 5 years before diagnosis of neurodegenerative disease were excluded to reduce the influence of surveillance bias and reverse causation. The analysis included 291,941 AD cases (median age at diagnosis: 76.2 years; male: 46.6%), 103,919 PD cases (74.3; 55.1%), and 10,161 ALS cases (69.3; 56.8%). A hospital-treated infection 5 or more years earlier was associated with an increased risk of AD (OR = 1.16, 95% CI: 1.15 to 1.18, P < 0.001) and PD (OR = 1.04, 95% CI: 1.02 to 1.06, P < 0.001). Similar results were observed for bacterial, viral, and other infections and among different sites of infection including gastrointestinal and genitourinary infections. Multiple infections before age 40 conveyed the greatest risk of AD (OR = 2.62, 95% CI: 2.52 to 2.72, P < 0.001) and PD (OR = 1.41, 95% CI: 1.29 to 1.53, P < 0.001). The associations were primarily due to AD and PD diagnosed before 60 years (OR = 1.93, 95% CI: 1.89 to 1.98 for AD, P < 0.001; OR = 1.29, 95% CI: 1.22 to 1.36 for PD, P < 0.001), whereas no association was found for those diagnosed at 60 years or older (OR = 1.00, 95% CI: 0.98 to 1.01 for AD, P = 0.508; OR = 1.01, 95% CI: 0.99 to 1.03 for PD, P = 0.382). No association was observed for ALS (OR = 0.97, 95% CI: 0.92 to 1.03, P = 0.384), regardless of age at diagnosis. Excluding infections experienced within 10 years before diagnosis of neurodegenerative disease confirmed these findings. Study limitations include the potential misclassification of hospital-treated infections and neurodegenerative diseases due to incomplete coverage of the National Patient Register, as well as the residual confounding from unmeasured risk or protective factors for neurodegenerative diseases., Conclusions: Hospital-treated infections, especially in early- and mid-life, were associated with an increased risk of AD and PD, primarily among AD and PD cases diagnosed before 60 years. These findings suggest that infectious events may be a trigger or amplifier of a preexisting disease process, leading to clinical onset of neurodegenerative disease at a relatively early age. However, due to the observational nature of the study, these results do not formally prove a causal link., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: JL coordinates a study (independent of the present study) on behalf of the Swedish IBD quality register (SWIBREG). That study has received funding from Janssen Corporation. Other authors declared no competing interests.

Background: Studying whether medications act as potential risk factors for amyotrophic lateral sclerosis (ALS) can contribute to the understanding of disease etiology as well as the identification of novel therapeutic targets. Therefore, we conducted a systematic review to summarize the existing evidence on the association between medication use and the subsequent ALS risk., Methods: A systematic review was conducted in Medline, Embase, and Web of Science from the date of database establishment to December 10, 2021. References of identified articles were further searched for additional relevant articles. Studies were included if (1) published in English, (2) explored medication use as exposure and development of ALS as outcome, and (3) the design was a human observational study. Clinical trials, reviews, comments, editorials, and case reports were excluded. Quality assessment was performed using a pre-validated tool for non-randomized studies, the Newcastle-Ottawa Assessment Scale (NOS)., Results: Of the 4760 studies identified, 25 articles, including 13 case-control studies, five nested case-control studies, six cohort studies, and one retrospective chart review, were included in the review. Among these studies, there were 22 distinct study populations that included 171,407 patients with ALS, seven classes of medication examined, and 23 studies with a NOS ≥ 5. There was a general lack of agreement between studies on the associations of cholesterol-lowering drugs, anti-inflammatory drugs, immunosuppressants, antibiotics, oral contraceptives (OCs) or hormone replacement therapy (HRT), antihypertensive drugs, antidiabetics, and drugs for psychiatric and neurological disorders with the subsequent risk of ALS. However, it appeared that statins, aspirin, OCs/HRT, antihypertensives, and antidiabetics were unlikely related to a higher risk of ALS. The positive associations noted for antibiotics, antidepressants, and skeletal muscle relaxants might be attributable to prodromal symptoms of ALS., Conclusions: There is currently no strong evidence to link any medication use with ALS risk., (© 2022. The Author(s).)

Amyotrophic lateral sclerosis (ALS), characterized by a loss of motor neurons in the brain and spinal cord, is a relatively rare but currently incurable neurodegenerative disease. The global incidence of ALS is estimated as 1.75 per 100,000 person-years and the global prevalence is estimated as 4.1-8.4 per 100,000 individuals. Contributions from outside the central nervous system to the etiology of ALS have been increasingly recognized. Gut microbiome is one of the most quickly growing fields of research for ALS. In this article, we performed a comprehensive review of the results from existing animal and human studies, to provide an up-to-date summary of the current research on gut microbiome and ALS. In brief, we found relatively consistent results from animal studies, suggesting an altered gut microbiome composition in experimental ALS. Publication bias might however be a concern. Findings from human studies are largely inconclusive. A few animal and human studies demonstrated the usefulness of intervention with microbial-derived metabolites in modulating the disease progression of ALS. We discussed potential methodological concerns in these studies, including study design, statistical power, handling process of biospecimens and sequencing data, as well as statistical methods and interpretation of results. Finally, we made a few proposals for continued microbiome research in ALS, with the aim to provide valid, reproducible, and translatable findings., (© 2021 The Authors. Journal of Internal Medicine published by John Wiley & Sons Ltd on behalf of Association for Publication of The Journal of Internal Medicine.)

Background: Evidence has accumulated to support the involvement of gastrointestinal (GI) dysfunction, possibly via gut microbial dysbiosis and alterations in the enteric nervous system, in the pathophysiology of different neurodegenerative diseases. However, whether patients with GI dysfunction have altered risk of amyotrophic lateral sclerosis (ALS) remains unknown. Methods: Based on a historical nationwide cohort study-ESPRESSO-in Sweden, we compared the risk of ALS among individuals with a previous GI biopsy finding of normal mucosa or non-specific inflammation, as two conditions of GI dysfunction, to that of individuals without any GI biopsy. We identified all individuals with a GI biopsy result of either normal mucosa ( n  = 483,442) or non-specific inflammation ( n  = 566,663) during 1965-2016 in Sweden as the exposed groups. For each exposed individual, we randomly selected up to five controls from the general Swedish population after individual matching by age and sex. Both the exposed and unexposed individuals were followed from date of biopsy (exposed individuals) or date of selection (unexposed individuals) until ALS diagnosis, emigration out of Sweden, death, or 31 December 2016, whichever came first. Stratified Cox regression models were used to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs). Results: Compared to individuals without GI biopsy, individuals with a GI biopsy result of normal mucosa had an increased risk of ALS (HR = 1.22; 95%CI: 1.04-1.42) after excluding the first 2 years of follow-up to alleviate concern of surveillance bias. This increased risk was noted among male (HR = 1.20; 95%CI: 0.94-1.51) and female (HR = 1.23; 95%CI: 1.01-1.50), as well as among younger (<60 years; HR = 1.17; 95%CI: 0.94-1.44) and older (≥60 years; HR = 1.24; 95%CI: 0.99-1.56) individuals. In contrast, no association was observed for a GI biopsy result of non-specific inflammation (HR = 1.00; 95%CI: 0.88-1.15). Neither of the GI biopsy results was related to the mortality risk after ALS diagnosis. Conclusions: Individuals with a GI biopsy result of normal mucosa-representing potentially a distinct type of GI dysfunction-had a higher future risk of ALS. No association was however noted for a GI biopsy result of non-specific inflammation. Further studies are needed to validate this finding and to understand the underlying reasons for the contrasting result pattern.

The use of proton pump inhibitors (PPIs) has been proposed as a potential risk factor for neurodegenerative diseases, but little is known regarding its role in amyotrophic lateral sclerosis (ALS). We therefore aimed to assess the association of PPI use with the subsequent risk of ALS, and performed a register-based nationwide nested case-control study, including 2,484 ALS cases diagnosed during July 2006-December 2013 in Sweden and 10 population controls per case that were individually matched to the case by sex, age, and area of residence. Dispenses and cumulative defined daily doses (cDDDs) of PPIs were extracted from the Swedish Prescribed Drug Register. The association of PPI use with the risk of ALS was assessed using conditional logistic regression, after applying different lag windows to avoid reverse causation. ALS patients were more likely to be dispensed with PPIs before diagnosis than controls. However, previous PPI use was not associated with an increased risk of ALS (OR = 1.08, 95% CI 0.97-1.19), and there was no dose-response relationship between cDDDs of PPIs and ALS risk (p = 0.0874), after excluding dispenses during the year before ALS diagnosis. The results were similar after excluding dispenses during the 2 or 3 years before ALS diagnosis.