Identifying potential risk factors for developing amyotrophic lateral sclerosis

A geographical study on amyotrophic lateral sclerosis in Rio Grande Do Norte, Brazil, from 2005 to 2018

OBJECTIVE

amyotrophic lateral sclerosis (ALS) is a rare and fatal neurodegenerative disorder with variable incidence and prevalence worldwide. However, clinical-epidemiological studies on ALS are scarce in Brazil. Thus, this study investigated whether ALS incidence had uniform spatial distribution in population-based cluster analysis in Rio Grande do Norte state (Brazil), from 2005 to 2018.

METHODS

new cases of ALS were identified in a database of the ALS multidisciplinary care center of the Onofre Lopes University Hospital in Natal (Rio Grande do Norte, Brazil). Approaches were based on incidence (empirical Bayes estimator and Moran's I analysis) and cluster analyses (Moran scatter plot and spatial correlogram).

RESULTS

a total of 177 patients (59% males) participated in the study; the mean age of ALS onset was 57 years. Mean annual incidence of ALS was 0.3769 per 100,000 inhabitants (95% confidence interval of 0.0889), higher in males than in females (0.4516 per 100,000 vs. 0.3044 per 100,000). According to spatial statistics, patients were homogeneously distributed throughout the studied area.

CONCLUSION

a low estimate was observed compared with other populations. Results did not indicate areas of increased risk or significant spatial geographic dependence, suggesting a random ALS incidence in Rio Grande do Norte.

Association between alcohol exposure and the risk of amyotrophic lateral sclerosis in the Euro-MOTOR study

OBJECTIVES

Several studies focused on the association between alcohol consumption and amyotrophic lateral sclerosis (ALS), although with inconsistent findings. Antioxidants may play a role since lyophilised red wine was found to prolong SOD1 mice lifespan. The aim of this international population-based case-control study performed in Ireland, The Netherlands and Italy was to assess the role of alcohol, and red wine in particular, in developing ALS.

METHODS

Euro-MOTOR is a case-control study where patients with incident ALS and controls matched for gender, age and area of residency were recruited in a population-based design. Logistic regression models adjusted for sex, age, cohort, education, leisure time physical activity, smoking, heart problems, hypertension, stroke, cholesterol and diabetes were performed.

RESULTS

1557 patients with ALS and 2922 controls were enrolled in the study. Exposure to alcohol drinking was not significantly associated with ALS risk. A stratified analysis of exposure to alcohol by cohort revealed significant ORs in The Netherlands and in Apulia, with opposite directions (respectively 0.68 and 2.38). With regard to red wine consumption, only in Apulia the double-fold increased risk (OR 2.53) remained significant. A decreased risk was found for current alcohol drinkers (OR 0.83), while a significantly increased risk was detected among former drinkers (OR 1.63). Analysis of cumulative exposure to alcohol revealed no significant associations with ALS risk.

CONCLUSION

With few exceptions, no significant association was found between alcohol consumption and ALS. The study of the association between alcohol and ALS requires a thorough exploration, especially considering the role of different type of alcoholic beverages.

Epidemiological evidence that physical activity is not a risk factor for ALS

To elucidate whether physical activity (PA) and sport increase the risk of developing amyotrophic lateral sclerosis (ALS), a literature review of epidemiological studies was conducted according to the Meta-analysis of Observational Studies in Epidemiology guidelines. Six databases (Pubmed, Scopus, ScienceDirect, IngentaConnect, Refdoc and the Cochrane database) were searched to April 2014. Experts were asked to identify studies in press. Studies of interest were examined for their level of evidence and synthetized using Armon's classification for exogenous risk factors for ALS. Of 37 epidemiological works included in the review, two (5.5%) provided class I evidence, and five (13.5%) class II. Others offered evidence of class III (n = 8, 21.6%), IV (n = 16, 43.2%) and V (n = 6, 16.2%). Results were stratified according to type of exposure: (1) PA related to sport and work (n = 14), (2) soccer and American football (n = 9), (3) occupation (n = 12), (4) proxies of PA (n = 2). Among articles which considered "PA related to sport and work", two class I studies and one class II study concluded that PA is not a risk factor for ALS. This evidence establishes (level A) that PA is not a risk factor for ALS. As regards "occupational related activity" a level of evidence of U was obtained (it is unknown whether the professional category "physical worker" is a risk factor for ALS). Football/soccer may be considered as a possible risk factor for ALS (level C) and there is a need for further research taking into account the numerous confounding factors that may arise in this field.

Genetic counselling in ALS: facts, uncertainties and clinical suggestions

The clinical approach to patients with amyotrophic lateral sclerosis (ALS) has been largely modified by the identification of novel genes, the detection of gene mutations in apparently sporadic patients, and the discovery of the strict genetic and clinical relation between ALS and frontotemporal dementia (FTD). As a consequence, clinicians are increasingly facing the dilemma on how to handle genetic counselling and testing both for ALS patients and their relatives. On the basis of existing literature on genetics of ALS and of other late-onset life-threatening disorders, we propose clinical suggestions to enable neurologists to provide optimal clinical and genetic counselling to patients and families. Genetic testing should be offered to ALS patients who have a first-degree or second-degree relative with ALS, FTD or both, and should be discussed with, but not offered to, all other ALS patients, with special emphasis on its major uncertainties. Presently, genetic testing should not be proposed to asymptomatic at-risk subjects, unless they request it or are enrolled in research programmes. Genetic counselling in ALS should take into account the uncertainties about the pathogenicity and penetrance of some genetic mutations; the possible presence of mutations of different genes in the same individual; the poor genotypic/phenotypic correlation in most ALS genes; and the phenotypic pleiotropy of some genes. Though psychological, social and ethical implications of genetic testing are still relatively unexplored in ALS, we recommend multidisciplinary counselling that addresses all relevant issues, including disclosure of tests results to family members and the risk for genetic discrimination.