Physical activity and amyotrophic lateral sclerosis: A European population-based case-control study

Amyotrophic lateral sclerosis and environmental factors

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that affects central and peripheral motor neuron cells. Its etiology is unknown, although a relationship between genetic background and environmental factors may play a major role in triggering the neurodegeneration. In this review, we analyze the role of environmental factors in ALS: heavy metals, electromagnetic fields and electric shocks, pesticides, β-N-methylamino-L-alanine, physical activity and the controversial role of sports. The literature on the single issues is analyzed in an attempt to clarify, as clearly as possible, whether each risk factor significantly contributes to the disease pathogenesis. After summarizing conflicting observations and data, the authors provide a final synthetic statement.

Motor neuron disease: biomarker development for an expanding cerebral syndrome

Descriptions of motor neuron disease (MND) documented more than a century ago remain instantly recognisable to the physician. The muscle weakness, typically with signs of upper and lower motor neuron dysfunction, is uniquely relentless. Over the last 30 years, a wider cerebral pathology has emerged, despite the lack of overt cognitive impairment in the majority of patients. From the initial linkage of a small number of cases to mutations in SOD1, diverse cellular pathways have been implicated in pathogenesis. An increasingly complex clinical heterogeneity has emerged around a significant variability in survival. Defining a cellular signature of aggregated TDP-43 common to nearly all MND and a large proportion of frontotemporal dementia (FTD), has placed MND alongside more traditional cerebral neurodegeneration. With new genetic causes, most notably a hexanucleotide expansion in C9orf72 associated with both MND and FTD, the development of biomarkers against which to test therapeutic candidates is a priority.

Pathogenesis of amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) or motor neuron disease is a rapidly progressive neurodegenerative disorder. The primary involvement is of motor neurons in the brain, spinal cord and peripherally. There is secondary weakness of muscles and primary involvement of other brain regions, especially involving cognition.

SOURCES OF DATA

Peer-reviewed journal articles and reviews. PubMed.gov

AREAS OF AGREEMENT

The pathogenesis of ALS remains largely unknown. There are a wide range of potential mechanisms related to neurodegeneration. An increasing number of genetic factors are recognized.

AREAS OF CONTROVERSY

There remains controversy, or lack of knowledge, in explaining how cellular events manifest as the complex human disease. There is controversy as to how well cellular and animal models of disease relate to the human disease.

GROWING POINTS

Large-scale international collaborative genetic epidemiological studies are replacing local studies. Therapies related to pathogenesis remain elusive, with the greatest advances to date relating to provision of care (including multidisciplinary management) and supportive care (nutrition and respiratory support).

AREAS TIMELY FOR DEVELOPING RESEARCH

The identification of C9orf72 hexanucleotide repeats as the most frequent genetic background to ALS, and the association with frontotemporal dementia, gives the potential of a genetic background against which to study other risk factors, triggers and pathogenic mechanisms, and to develop potential therapies.

Cardiovascular disease and diagnosis of amyotrophic lateral sclerosis: A population based study

Amyotrophic lateral sclerosis (ALS) is a rapidly fatal neurodegenerative disease of unknown etiology. We investigated the association between ALS diagnosis and prior cardiovascular disease (CVD), and CVD-specific, hospital admissions in the Danish population. We conducted a population based nested case-control study, including 3182 Danish residents diagnosed with ALS at age ≥20 years (1982-2009) and 100 randomly selected controls for each case, matched on age, gender and vital status. We estimated odds ratios (OR) associated with CVD, and CVD-specific hospital admissions, adjusting for socioeconomic and marital status, region of residence and past diabetes and obesity diagnoses. The estimated adjusted OR for any CVD admission at least three years prior to the date of ALS diagnosis was 1.15 (95% CI 1.04-1.27). Our results varied across cause-specific admissions; for atherosclerosis the OR was 1.36 (95% CI 1.02-1.80) and for ischemic heart disease 1.14 (95% CI 0.99-1.31), while we observed no association with hypertensive and cerebrovascular diseases. Adjusting for or stratifying by COPD status, a cigarette-smoking correlate, did not change our results. In conclusion, in our population based study we found evidence for a moderately elevated association with CVD that was stronger for specific conditions, such as atherosclerosis. Our findings may have important implications for ALS pathogenesis.

Long-term physical activity: an exogenous risk factor for sporadic amyotrophic lateral sclerosis?

OBJECTIVES

To conduct a geographically defined, UK-based case-control study, to examine any association between physical activity (PA) and amyotrophic lateral sclerosis (ALS).

METHODS

A novel historical PA questionnaire was designed, validated, and subsequently administered in individual face-to-face interviews of 175 newly diagnosed sporadic ALS cases and 317 age- and sex-matched community controls. Historical PA energy expenditure and time spent in vigorous-intensity PA were derived from questionnaire data and compared between cases and controls.

RESULTS

Participation in an extra 10kJ/kg/day of PA (equivalent to approximately 45minutes brisk walking) was consistently associated with an increased risk of ALS, with the strongest association observed for adulthood exercise-related PA (OR 1.47, 95% CI 1.10-1.97). An extra 10mins/day of vigorous PA was also associated with the odds of ALS (OR 1.03, 95% CI 1·01-1·05). Results were slightly attenuated following adjustment for smoking and educational attainment.

CONCLUSIONS

To our knowledge this is the first study to demonstrate a positive association between ALS and PA participation using a specifically designed and validated historical PA questionnaire. Despite the well-established health benefits of PA, a high activity lifestyle may also be associated with elevated risk of ALS. Large-scale prospective studies in the future may help to confirm this association.

Recent advances in amyotrophic lateral sclerosis

ALS is a relentlessly progressive and fatal disease, with no curative therapies available to date. Symptomatic and palliative care, provided in a multidisciplinary context, still remains the cornerstone of ALS management. However, our understanding of the molecular mechanisms underlying the disease has advanced greatly over the past years, giving new hope for the development of novel diagnostic and therapeutic approaches. Here, we have reviewed the most recent studies that have contributed to improving both clinical management and our understanding of ALS pathogenesis.

No association between soil constituents and amyotrophic lateral sclerosis relative risk in Ireland

INTRODUCTION

We have recently mapped ALS spatial risk in Ireland using Bayesian and cluster analysis methods at electoral division (ED) and small area (SA) levels. As a number of metal elements (both minerals and toxins) have been proposed as risk factors for ALS, here we extend this analysis to include soil constituents from the Irish National Soils Database as Bayesian conditional auto-regression covariates to determine associations with small area ALS risk.

METHODS

Data on 45 different soil parameters were obtained under license from National Soils Database (via Irish EPA). We interpolated average values of each soil constituent for each small area using ordinary kriging. All cases of ALS in Ireland from January 1995 to December 2013 were identified from the Irish ALS register and observed and age and gender standardised expected cases were calculated for each SA. Besag-York-Mollié (BYM) models were then built including each parameter from the national soils database in turn as a Bayesian covariate in the BYM model. Models were compared using the deviance information criterion (DIC) and separate models were built for ALS subtypes.

RESULTS

1701 ALS patients were included - 959 (56%) were male, 938 (55%) had limb onset ALS. 315 Bayesian models were built in total. Of the 315 models built, only one resulted in a coefficient that did not overlap zero. For limb onset cases, total magnesium had a mean coefficient of 0.319 (credible interval 0.033-0.607).

DISCUSSION

We report the first spatial analysis of potential association between ALS and soil minerals using a population-based dataset collected over 18 years. Our sole non-zero finding is likely a random finding due to the high number of models built. We did not find any evidence to support soil mineral and toxin levels as risk factors for ALS. However as soil parameters are an ecological assessment of exposure in a given area, individual level measures of exposure are required.

Participation in Physical Activity and Risk for Amyotrophic Lateral Sclerosis Mortality Among Postmenopausal Women

IMPORTANCE

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal disease with no known cause. Case studies primarily of athletes and several case-control studies have suggested that high levels of strenuous physical activity (PA) may increase the risk for ALS. This relationship has yet to be evaluated among women in population-based cohort studies.

OBJECTIVE

To evaluate the relationship between PA and risk for ALS mortality in a large cohort of postmenopausal women.

DESIGN, SETTING, AND PARTICIPANTS

The Women's Health Initiative (WHI) enrolled 161 809 postmenopausal women, aged 50 to 79 years (mean [SD] age, 63.6 [7.24] years), between 1993 and 1998 into either a clinical trial or an observational study at 40 clinical research centers across the United States. We conducted a cohort study from November 2014 to September 2015 using baseline and mortality data during an average of 9.6 years of follow-up from the entire WHI cohort, through September 1, 2013 (with 1.1% lost to follow-up), to address whether there is a relationship between PA and ALS mortality.

EXPOSURES

The WHI assessed frequency and duration of mild, moderate, and strenuous PA at baseline via self-administered questionnaire.

MAIN OUTCOMES AND MEASURES

Underlying cause of death from ALS collected from death certificates.

RESULTS

The WHI enrolled 161 809 women, of whom 165 died of ALS; women who died of ALS were older (median age, 66 years; interquartile range, 61-69 years) compared with the total WHI study population (median age, 63 years; interquartile range, 57-69 years). Age-adjusted ALS mortality rates varied from 7.4 (95% CI, 5.5-9.9)/100 000 person-years for no strenuous PA to 10.6 (95% CI, 5.6-20.0)/100 000 person-years for strenuous PA 3 or more days per week (P = .07). Adjusted for age and body mass index (calculated as weight in kilograms divided by height in meters squared), the odds ratio for death from ALS for participants with strenuous PA 3 or more days per week compared with no reported strenuous PA was 1.56 (95% CI, 1.02-2.37; P = .04).

CONCLUSIONS AND RELEVANCE

To our knowledge, this is the first cohort study to report an increased risk for ALS mortality associated with strenuous PA in postmenopausal women. The association between strenuous PA and ALS risk observed does not compromise the overall benefit of strenuous PA for total mortality, coronary heart disease, and breast cancer reported in other WHI investigations, but it may provide an important clue to the etiology of ALS, if replicated by other studies.

Physical activity and risk of Amyotrophic Lateral Sclerosis in a prospective cohort study

Previous case-control studies have suggested a possible increased risk of Amyotrophic Lateral Sclerosis (ALS) with physical activity (PA), but this association has never been studied in prospective cohort studies. We therefore assessed the association between PA and risk of death from ALS in the European Prospective Investigation into Cancer and Nutrition. A total of 472,100 individuals were included in the analysis, yielding 219 ALS deaths. At recruitment, information on PA was collected thorough standardised questionnaires. Total PA was expressed by the Cambridge Physical Activity Index (CPAI) and analysed in relation to ALS mortality, using Cox hazard models. Interactions with age, sex, and anthropometric measures were assessed. Total PA was weakly inversely associated with ALS mortality with a borderline statistically significant trend across categories (p = 0.042), with those physically active being 33% less likely to die from ALS compared to those inactive: HR = 0.67 (95% CI 0.42-1.06). Anthropometric measures, sex, and age did not modify the association with CPAI. The present study shows a slightly decreased-not increased like in case-control studies-risk of dying from ALS in those with high levels of total PA at enrolment. This association does not appear confounded by age, gender, anthropometry, smoking, and education. Ours was the first prospective cohort study on ALS and physical activity.

Physical Trauma and Amyotrophic Lateral Sclerosis: A Population-Based Study Using Danish National Registries

Prior studies have suggested that physical trauma might be associated with the development of amyotrophic lateral sclerosis (ALS). We conducted a population-based, individually matched case-control study in Denmark to assess whether hospitalization for trauma is associated with a higher risk of developing ALS. There were 3,650 incident cases of ALS in the Danish National Patient Register from 1982 to 2009. We used risk-set sampling to match each case to 100 age- and sex-matched population controls alive on the date of the case's diagnosis. Odds ratios and 95% confidence intervals were calculated using a conditional logistic regression model. History of trauma diagnosis was also obtained from the Danish Patient Register. When traumas in the 5 years prior to the index date were excluded, there was a borderline association between any trauma and ALS (odds ratio (OR) = 1.09, 95% confidence interval (CI): 0.99, 1.19). A first trauma before age 55 years was associated with ALS (OR = 1.22, 95% CI: 1.08, 1.37), whereas first traumas at older ages were not (OR = 0.97, 95% CI: 0.85, 1.10). Our data suggest that physical trauma at earlier ages is associated with ALS risk. Age at first trauma could help explain discrepancies in results of past studies of trauma and ALS.

Epidemiology of amyotrophic lateral sclerosis: A review of literature

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of motor neurons, resulting in worsening weakness of voluntary muscles until death occurs from respiratory failure. The incidence of ALS in European populations is two to three people per year per 100,000 of the general population. In Europe, crude prevalences range from 1.1/100,000 population in Yugoslavia to 8.2/100,000 in the Faroe Islands. Major advances have been made in our understanding of the genetic causes of ALS, whereas the contribution of environmental factors has been more difficult to assess and large-scale studies have not yet revealed a replicable, definitive environmental risk factor. The only established risk factors to date are older age, male gender and a family history of ALS. Median survival time from onset to death is usually 3 years from the first appearance of symptoms. Older age and bulbar onset are consistently reported to have poorer outcomes. However, there are conflicting data regarding gender, diagnostic delay and El Escorial criteria. The rate of symptom progression has been revealed to be an independent prognostic factor. Psychosocial factors and impaired cognitive function are negatively related to ALS outcome, while nutritional status and respiratory function are also related to ALS prognosis. The effect of enteral nutrition on survival is still unclear, although noninvasive positive pressure ventilation (NIPPV) has been found to improve survival. These findings have relevant implications for the design of future trials.

Designing an Internationally Accessible Web-Based Questionnaire to Discover Risk Factors for Amyotrophic Lateral Sclerosis: A Case-Control Study

Background

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease with a typical survival of three to five years. Epidemiological studies using paper-based questionnaires in individual countries or continents have failed to find widely accepted risk factors for the disease. The advantages of online versus paper-based questionnaires have been extensively reviewed, but few online epidemiological studies into human neurodegenerative diseases have so far been undertaken.

Objective

To design a Web-based questionnaire to identify environmental risk factors for ALS and enable international comparisons of these risk factors.

Methods

A Web-based epidemiological questionnaire for ALS has been developed based on experience gained from administering a previous continent-wide paper-based questionnaire for this disease. New and modified questions have been added from our previous paper-based questionnaire, from literature searches, and from validated ALS questionnaires supplied by other investigators. New criteria to allow the separation of familial and sporadic ALS cases have been included. The questionnaire addresses many risk factors that have already been proposed for ALS, as well as a number that have not yet been rigorously examined. To encourage participation, responses are collected anonymously and no personally identifiable information is requested. The survey is being translated into a number of languages which will allow many people around the world to read and answer it in their own language.

Results

After the questionnaire had been online for 4 months, it had 379 respondents compared to only 46 respondents for the same initial period using a paper-based questionnaire. The average age of the first 379 web questionnaire respondents was 54 years compared to the average age of 60 years for the first 379 paper questionnaire respondents. The questionnaire is soon to be promoted in a number of countries through ALS associations and disease registries.

Conclusions

Web-based questionnaires are a time- and resource-efficient method for performing large epidemiological studies of neurodegenerative diseases such as ALS. The ability to compare risk factors between different countries using the same analysis tool will be of particular value for finding robust risk factors that underlie ALS.

Acute Traumatic Brain Injury Does Not Exacerbate Amyotrophic Lateral Sclerosis in the SOD1 (G93A) Rat Model

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease in which upper and lower motor neurons degenerate, leading to muscle atrophy, paralysis, and death within 3 to 5 years of onset. While a small percentage of ALS cases are genetically linked, the majority are sporadic with unknown origin. Currently, etiological links are associated with disease onset without mechanistic understanding. Of all the putative risk factors, however, head trauma has emerged as a consistent candidate for initiating the molecular cascades of ALS. Here, we test the hypothesis that traumatic brain injury (TBI) in the SOD1^G93A transgenic rat model of ALS leads to early disease onset and shortened lifespan. We demonstrate, however, that a one-time acute focal injury caused by controlled cortical impact does not affect disease onset or survival. Establishing the negligible involvement of a single acute focal brain injury in an ALS rat model increases the current understanding of the disease. Critically, untangling a single focal TBI from multiple mild injuries provides a rationale for scientists and physicians to increase focus on repeat injuries to hopefully pinpoint a contributing cause of ALS.

Risk factors for amyotrophic lateral sclerosis

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

Head trauma in sport and neurodegenerative disease: an issue whose time has come?

A number of small studies and anecdotal reports have been suggested that sports involving repeated head trauma may have long-term risks of neurodegenerative disease. There are now plausible mechanisms for these effects, and a recognition that these problems do not just occur in former boxers, but in a variety of sports involving repeated concussions, and possibly also in sports in which low-level head trauma is common. These neurodegenerative effects potentially include increased risks of impaired cognitive function and dementia, Parkinson's disease, and amyotrophic lateral sclerosis. Many would argue for taking a precautionary approach and immediately banning or restricting sports such as boxing. However, there are important public health issues in terms of how wide the net should be cast in terms of other sports, and what remedial measures could be taken? This in turn requires a major research effort involving both clinical and basic research to understand the underlying mechanisms, leading from head trauma to neurodegenerative disease and epidemiologic studies to assess the long-term consequences.

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.