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Cited by 29Amyotrophic Lateral Sclerosis ResearchTraumatic Brain Injury ResearchSpinal Cord Injury Research

Prevalence of potential sports‐associated risk factors in Swiss amyotrophic lateral sclerosis patients

Open access
Feddermann‐Demont, Nina, Junge, Astrid, Weber, Konrad P., Weller, Michael, Dvořák, Jiří, Tarnutzer, Alexander A.·2017·Brain and Behavior
DOI 10.1002/brb3.630PMC PMC5390828
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Abstract

Objectives: Amyotrophic lateral sclerosis (ALS) has been reported to occur with increased incidence amongst physically active people. The role of extrinsic risk factors as physical activity, head trauma and drug/pesticide‐exposure in the pathophysiology of ALS and especially in the context of practising sports remains controversial. Materials and Methods: We retrospectively studied exposure to extrinsic factors in 92 ALS patients in the presymptomatic stage. Metabolic equivalents (METs) were calculated and the association of physical activity, drug intake, head trauma and participation in specific sports (football [soccer], ice hockey) with age at symptom‐onset was evaluated. Results: Ninety‐five percent of patients considered themselves physically active before symptom‐onset. Total MET‐values varied broadly and there was no correlation between vigorous physical activity and age at symptom‐onset. Mild traumatic brain injury (prevalence = 16.7%) was the most frequent diagnosis after head/neck injury. A history of ≥1 head/neck injuries was associated with a younger age at symptom‐onset (61.8 ± 11.0 vs. 54.1 ± 13.0, p = .013). In former football and ice hockey players the rate of vigorous physical activities was increased (p < .05), whereas total MET‐values, frequency of head injuries and analgesic intake were not different compared to other ALS patients. Conclusions: History of head injuries was the only extrinsic risk factor associated with accelerated neurodegeneration in ALS. There was no evidence for extrinsic factors predisposing former football and ice hockey players to ALS. Our data therefore support the hypothesis that not increased physical activity per se, but other unknown environmental factors and/or genetic profile or lifestyle‐promoting physical fitness increases ALS susceptibility.

AI snapshot

Written from the paper’s full text.

TL;DR

In 92 Swiss ALS patients, a history of head/neck injury was associated with younger age at symptom onset, while vigorous physical activity was not. Former football and ice hockey players showed more vigorous activity but no clear excess of head injuries, analgesic intake, or significantly earlier symptom onset.

Key findings

  • Ninety-five percent of patients considered themselves physically active before symptom onset; vigorous physical activities were identified in 51.1%. There was no correlation between vigorous physical activity and age at symptom onset (p = .247), while higher total MET values correlated with later symptom onset (Pearson correlation = .201, p = .032).
  • A history of ≥1 head/neck injuries was associated with younger age at symptom onset (54.1 ± 13.0 vs. 61.8 ± 11.0 years, p = .013). Mild traumatic brain injury was the most frequent diagnosis after head/neck injury (prevalence = 16.7%).
  • Former football and ice hockey players had a higher rate of vigorous physical activities (80.0% vs. 45.5%; OR 4.8, 95% CI 1.3–18.4), but total MET values, frequency of head injuries, and analgesic intake were not different from other ALS patients.
  • Former football/ice hockey players did not show significantly earlier symptom onset: male football players 52.7 ± 13.4 vs. 57.8 ± 11.9 years (p = .237), male ice hockey players 50.4 ± 15.3 vs. 57.3 ± 11.9 years (p = .237), and female football players 59 vs. 62.2 ± 11.0 years (p = .776). None of the former football players reported exposure to fertilizers, pesticides, herbicides, or solvents.

Methods

  • Retrospective questionnaire study of 92 ALS patients from the registry of the Swiss Federation for Joint Tasks of Health Insurers (SVK); all 175 ALS patients who submitted riluzole requests in 2011 were contacted, with a response rate of 52.6% (92/175).
  • A 44-question anonymous questionnaire covered disease onset and current symptoms (including ALS functional rating scale), head injuries, drug intake, and presymptomatic physical activities, with specific questions on football and ice hockey.
  • Metabolic equivalents (METs) were calculated; total MET values = MET value × duration in years × hours per week, and vigorous activity was defined as MET >6. ANOVA and odds ratios were used (SPSS Version 22). Former football/ice hockey participation was defined as participating in a club or school team at least once a week for at least 1 year.

Limitations

  • The paper states that the retrospective, questionnaire-based design carries potential recall bias; there was no age- and gender-matched control group; the ~50% response rate risks selection bias, including language bias because only a German-language questionnaire was available (88% reported German as mother tongue); and sports-inclined patients may have been more willing to participate, possibly overestimating the role of physical activity.
  • Evident from the text: the sample and sport subgroups were small (11 football players, 5 ice hockey players), limiting statistical power; exposures and diagnoses were self-reported; and without a control population, rates such as physical activity and MET values could not be compared with the general Swiss population. The paper also notes that pesticide/solvent exposure may have remained unrecognized by former football players.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1002/brb3.630

Cites

38 of 38 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

8 of 33 cited sources checked · 7 supported · 0 flagged · accuracy not yet measured

  • Findingown data

    None of the patients reported former intake of performance-enhancing substances such as anabolic steroids.

    “None of the patients (n = 89, missing value in three subjects) reported former intake of performance‐enhancing substances such as anabolic steroids.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
  • Findingown data

    Total MET values varied broadly among the ALS patients.

    “Total MET‐values varied broadly”
    • Also stated in: § Physical activity profiles before symptom‐onset · plain
      “individual total MET values varied considerably between patients”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
  • Findingown data

    Higher total MET values were correlated with later age at symptom onset (n = 91, Pearson correlation = .201, p = .032).

    “Higher total MET values were correlated with symptom‐onset later in life (n = 91, missing value in 1 subject, Pearson correlation = .201, p = .032)”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
  • Findingown data

    Vigorous physical activities were identified in 51.1% of patients.

    “Vigorous physical activities were identified in 51.1% of patients.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
  • Findingown data

    Analgesic intake was not different between former football/ice hockey players and other ALS patients.

    “rates of analgesic intake were not different (Table 4).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
  • May combine two claims. 20
  • Classified as probably not a substantial claim. 21

  • May combine two claims.

    Premisecitation

    In two studies, excess occurrence of head injury was significant only within 1 year after head injury, suggesting accidents provoked by early signs of ALS rather than ALS secondary to head trauma.

    “However, in two studies excess occurrence was significant only within 1 year after head injury (Peters et al., 2013; Turner et al., 2010), rather suggesting accidents provoked by early signs of ALS than ALS secondary to head trauma (Turner et al., 2010).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites Peters et al., 2013 source
    • cites Turner et al., 2010

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Increased risk of ALS has been reported in Italian football players, American football players, and sport-related physical exercise in general.

    “While an increased risk has been reported in Italian football players (Belli & Vanacore, 2005; Chio et al., 2005), American football players (Lehman et al., 2012), and sport‐related physical exercise in general (Beghi et al., 2010), no such link has been found in population‐based case–control studies in Europe (Pupillo et al., 2014) and the US (Longstreth et al., 1998).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites Belli & Vanacore, 2005 source
    • cites Chio et al., 2005

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Lehman et al., 2012 source

  • May combine two claims.

    Premisecitation

    In a Dutch study, rates of vigorous physical activities were not different between patients and controls (16% vs 14%, adjusted OR=1.24, 95% CI=0.96-1.61), not supporting an association between vigorous physical activity and ALS risk.

    “Likewise, rates for participants with vigorous physical activities (including marathon and triathlon) were not different for patients and controls (16% vs. 14%, adjusted OR = 1.24, 95%‐CI = 0.96–1.61) in a Dutch study, not supporting an association between vigorous physical activity and the ALS risk (Huisman et al., 2013).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Huisman et al., 2013 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The hypothesis that not increased physical activity per se but other factors increase ALS susceptibility was supported by the observed discrepancy between increased risk with higher leisure time physical activities and lack of association with occupational physical activity and absence of dose-response relationship.

    “This hypothesis was supported by the observed discrepancy between an increased risk for ALS with higher levels of leisure time physical activities and lack of association of ALS risk and occupational physical activity and the absence of a dose–‐response relationship (Huisman et al., 2013).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Huisman et al., 2013 source

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    It was proposed that not increased physical activity per se, but rather a yet unknown genetic profile or lifestyle-promoting physical fitness increases ALS susceptibility.

    “With several extensive literature reviews reporting no evidence for a link between sports‐ or work‐related physical activity and ALS (Armon, 2007; Hamidou et al., 2014; Veldink et al., 2005), it was proposed that not increased physical activity per se, but rather a—yet unknown—genetic profile or lifestyle‐promoting physical fitness increases ALS susceptibility (Huisman et al., 2013; Turner, Wotton”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Huisman et al., 2013 source
    • cites Turner et al., 2012

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingcitation

    The gender distribution (male-to-female ratio = 1.24:1) and gender-dependent differences in average age at symptom onset (56.8 vs 62.1 years) in the cohort were in line with values from previous ALS populations.

    “Furthermore, both the distribution of gender (male‐to‐female ratio = 1.24:1) and gender‐dependent differences in average age at symptom onset (56.8 vs. 62.1 years) were in line with values from previous ALS populations, reporting male‐to‐female ratios ranging between 0.8:1 and 2.7:1 (Alonso et al., 2009; Cronin et al., 2007; Uenal et al., 2014) and a tendency for earlier symptom‐onset in men than”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites Alonso et al., 2009 source

      The Results report 470 men and 360 women with MND, a male-to-female case ratio of about 1.31:1, consistent with the cited range. The Results and Discussion also report higher incidence in men. They do not report a sex-specific average age at symptom onset or establish earlier onset in men; the Results say incidence peaked at ages 75–79 in both sexes. No page numbers are available in our copy. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites Cronin et al., 2007 source
    • cites Uenal et al., 2014 source

  • May combine two claims.

    Interpretationcitation

    Our observations fit well into the hypothesis that not increased physical activity per se but other unknown environmental factors and/or an unknown genetic profile or lifestyle-promoting physical fitness increases ALS susceptibility.

    “While (repetitive) head traumata may be linked to earlier symptom onset, our observations fit well into the previously stated hypothesis that not increased physical activity per se but other unknown environmental factors and/or an—as yet unknown—genetic profile or lifestyle‐promoting physical fitness increases ALS susceptibility (Huisman et al., 2013).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Huisman et al., 2013 source

  • May combine two claims.

    Findingown data

    Eleven ALS patients participated in football (12.0%) and five in ice hockey (5.4%) regularly before symptom onset.

    “Eleven ALS patients participated in football (11/92, 12.0%) before symptom onset, five in ice hockey (5/92, 5.4%) regularly”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.

  • May combine two claims.

    Findingown data

    Total individual MET values were not dominated by football or ice hockey; other physical activities substantially contributed to total MET values.

    “However, total individual MET values were not dominated by football or ice hockey, i.e., other physical activities substantially contributed to total MET values as well.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Most frequent causes of head/neck injury were falls during activities of daily life and traffic-related accidents (8/26 each), followed by sports-related injuries (4/26) and work-related injuries (4/26).

    “Most frequent causes were falls during activities of daily life (8/26) and traffic‐related accidents (8/26), followed by sports‐related injuries (4/26) and work‐related injuries (4/26).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.

  • May combine two claims.

    Findingown data

    Former male football players became symptomatic earlier by on average 5.1 years, and ice hockey players by 6.9 years, but these differences were not significant.

    “While former male football players and ice hockey players became symptomatic earlier by on average 5.1 and 6.9 years, respectively, these differences were not significant.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Information on the presence/absence of previous head/neck injuries was provided by 70 patients (76.1%).

    “Information on the presence/absence of previous head/neck injuries was provided by 70 patients (76.1%).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Diagnosis of ALS was confirmed by the registry using a standardized registration form that distinguishes patients meeting accepted diagnostic criteria from ALS mimics.

    “Specifically, the SVK has designed a standardized registration form that systematically asks about ALS‐related findings in order to distinguish between patients that meet accepted diagnostic criteria for ALS (involvement of upper and lower motor neurons in at least two regions) and ALS mimics not eligible for riluzole.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Response rate for questionnaires was 52.6% (92/175).

    “Response rate for questionnaires was 52.6% (92/175).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The data support the hypothesis that not increased physical activity per se, but other unknown environmental factors and/or genetic profile or lifestyle-promoting physical fitness increases ALS susceptibility.

    “Our data therefore support the hypothesis that not increased physical activity per se, but other unknown environmental factors and/or genetic profile or lifestyle‐promoting physical fitness increases ALS susceptibility.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.
    • Rests on an assumption: The 52.6% response rate did not introduce selection bias that materially affects the observed associations.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Longstreth and colleagues hypothesized that the effect of toxins on motor neurons could be potentiated by vigorous physical activity.

    “Harwood and colleagues proposed that such a susceptibility could be reflected in a specific physical constitution with a relatively larger fraction of type 1 muscle fibers (Harwood et al., 2009) and Longstreth and colleagues hypothesized that the effect of toxins on motor neurons could be potentiated by vigorous physical activity (Longstreth, Nelson, Koepsell, & van Belle, 1991).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Longstreth et al., 1991 source

  • May combine two claims.

    Study design and conductown data

    Reasons for not having returned the questionnaire include death in the same year as registration and missing German-language skills.

    “Reasons for not having returned the questionnaire include death in the same year as registration to the registry used to identify ALS patients and missing German‐language skills (we only had a questionnaire available in German).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Exposure to fertilizers, pesticides/herbicides, or solvents may have remained unrecognized by the players.

    “While none of the former football players reported exposure to fertilizers, pesticides/herbicides, or solvents, such exposure may have remained unrecognized by the players.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    The study did not obtain a control population, so the rate of physical activity cannot be put in relation to the general Swiss population.

    “Since we did not obtain a control population, we cannot put this value in relation to the rate in the general Swiss population.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The higher rate of 95% physically active patients might be related to how the question was phrased in the questionnaire.

    “The higher rate of 95% of physically active patients obtained here might be related to how this question was phrased in the questionnaire.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationcitation

    Physical activity may be protective against motor neuron disease.

    “The positive correlation between total MET values and age at symptom onset is in line with recent work, suggesting that physical activity may eventually be even protective against motor neuron disease (Pupillo et al., 2014).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Pupillo et al., 2014 source

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Others considered an impact of drugs or dietary supplements on ALS as more likely.

    “An impact of drugs or dietary supplements was considered as more likely by others (Armon, 2007; Belli & Vanacore, 2005).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Armon, 2007 source
    • cites Belli & Vanacore, 2005 source

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductnone given

    Subgroup analyses within the case series could be performed without restrictions emerging from potential recall bias.

    “However, with a focus on sports‐related physical activities and their possible association with ALS, subgroup analyses could be performed within our case series without any restrictions emerging from this potential bias.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In one study, the rate of physically active people was lower in ALS patients (in the presymptomatic stage) than in controls (67% vs 74%, adjusted OR=0.65, 95% CI=0.48-0.89).

    “previously, the rate of physically active people was reportedly lower in ALS patients (in the presymptomatic stage) than in the controls (67% vs. 74%, adjusted OR = 0.65, 95%‐CI = 0.48–0.89) in one study (Pupillo et al., 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pupillo et al., 2014 source

  • May combine two claims.

    Study design and conductown data

    The study did not include an age- and gender-matched control group, limiting interpretation of findings.

    “We did not include an age‐ and gender‐matched control group in this study, which poses certain limitations on the interpretation of our findings, including the frequency of certain sports activities and the representativeness of MET‐values calculated.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    The questionnaire did not provide any requirements to qualify for "being physically active".

    “Noteworthy, we did not provide any requirements that had to be met to qualify for “being physically active” in our questionnaire.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Several extensive literature reviews report no evidence for a link between sports- or work-related physical activity and ALS.

    “With several extensive literature reviews reporting no evidence for a link between sports‐ or work‐related physical activity and ALS (Armon, 2007; Hamidou et al., 2014; Veldink et al., 2005), it was proposed that not increased physical activity per se, but rather a—yet unknown—genetic profile or lifestyle‐promoting physical fitness increases ALS susceptibility (Huisman et al., 2013; Turner, Wotton”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Armon, 2007 source
    • cites Hamidou et al., 2014 source
    • cites Veldink et al., 2005 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Anabolic steroids might increase the risk for ALS via their anabolic or androgen-like effect.

    “This includes anabolic steroids, which might increase the risk for ALS via their anabolic or androgen‐like effect (Armon, 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Armon, 2007 source

  • Classified as probably not a substantial claim.

    Premisecitation

    The role of physical activity, head trauma and drug/pesticide exposure in the pathophysiology of ALS, especially in the context of participation in specific sports, remains controversial.

    “Overall, the role of physical activity, head trauma and drug/pesticide exposure in the pathophysiology of ALS, and especially in the context of participation in specific sports remains controversial.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Beghi, 2013 source

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The positive correlation between total MET values and age at symptom onset may be explained by patients with later disease onset remaining physically active longer.

    “However, this finding must be interpreted with caution, as disease onset at higher age may have allowed those patients to remain physically active longer, resulting in higher total MET values.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Head injury may accelerate disease progression in ALS, resulting in earlier symptomatic presentation.

    “While not increasing the risk for ALS, head injury may accelerate disease progression, resulting in earlier symptomatic presentation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    The rates of physically active patients (95%) and vigorous physical activities (51%) in the ALS cohort were larger than in the literature.

    “Overall, both rates of patients that considered themselves physically active (95%) and reported vigorous physical activities during their presymptomatic stage (51%) were larger than in the literature: previously, the rate of physically active people was reportedly lower in ALS patients (in the presymptomatic stage) than in the controls (67% vs. 74%, adjusted OR = 0.65, 95%‐CI = 0.48–0.89) in one”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Pupillo et al., 2014 source

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Premisecitation

    Harwood and colleagues proposed that ALS susceptibility could be reflected in a specific physical constitution with a relatively larger fraction of type 1 muscle fibers.

    “Harwood and colleagues proposed that such a susceptibility could be reflected in a specific physical constitution with a relatively larger fraction of type 1 muscle fibers (Harwood et al., 2009) and Longstreth and colleagues hypothesized that the effect of toxins on motor neurons could be potentiated by vigorous physical activity (Longstreth, Nelson, Koepsell, & van Belle, 1991).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Harwood et al., 2009 source

  • May combine two claims.

    Interpretationown data

    One or several episodes of head trauma may accelerate neurodegeneration in ALS, resulting in earlier clinical manifestation.

    “Our data suggests that one or several episodes of head trauma may accelerate neurodegeneration in ALS, resulting in earlier clinical manifestation.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    Physically active/sports inclined patients may have been more willing to participate than average ALS patients, risking overestimation of the role of physical activities in ALS.

    “Due to the focus of this study on physical activities and sports, physically active/sports inclined patients may have been more willing to participate than average ALS patients. This bears a certain risk that our study overestimates the role of physical activities in ALS.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning

    The questionnaire focused on physical activities and sports many years or decades ago and controlled for age at exposure, making it unlikely that these activities were performed after disease onset.

    “However, the focus of our questionnaire was on physical activities and sports already many years or decades ago. This was also controlled by asking for age at exposure to a certain condition, making it unlikely that these activities were performed after onset of disease.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: There is an asymptomatic period in ALS.

  • May combine two claims.

    Interpretationown data

    The composition of the ALS population was representative for ALS as well as for participation in football.

    “This suggests that the composition of our ALS population was representative for this disorder as well as for participation in football.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Underlying mechanisms for the effect of head trauma on ALS may be related to microtrauma or oxidative stress of motor neurons.

    “Underlying mechanisms for such an effect remain unclear, but may be related to microtrauma or oxidative stress of motor neurons.”
    Quote in the paperNot a substantial claim
38 of 38

  • The paper relies on this without support.

    Patients' retrospective self-reports of presymptomatic physical activity, head injuries, and drug intake are accurate and not systematically biased.

    “invited to answer a questionnaire anonymously with 44 questions covering disease onset and current symptoms (including the ALS functional rating scale) as well as head injuries, intake of pharmaceuticals and physical activities in the presymptomatic stage”

  • The paper relies on this without support.

    Reported head/neck injuries occurred before ALS symptom onset and were not a consequence of early disease.

    “head injuries, intake of pharmaceuticals and physical activities in the presymptomatic stage”

  • The paper relies on this without support.

    The observed association between head injury history and younger age at symptom onset reflects a causal acceleration of neurodegeneration rather than reverse causation or confounding.

    “History of head injuries was the only extrinsic risk factor associated with accelerated neurodegeneration in ALS.”

  • The paper relies on this without support.

    The 52.6% response rate did not introduce selection bias that materially affects the observed associations.

    “Response rate for questionnaires was 52.6% (92/175).”

  • The paper relies on this without support.

    About 30% of Swiss inhabitants have a mother tongue other than German.

    “Taking in mind that about 30% of Swiss inhabitants having a mother tongue different than German, this likely suggest that there was a bias based on language.”

  • The authors state this as an assumption.

    The physical activity profile and course of disease in non-German-speaking Swiss inhabitants are not distinct from German-speaking ones.

    “However, there is no reason to assume that the physical activity profile or the course of disease in non‐German‐speaking Swiss inhabitants is distinct.”

  • The authors state this as an assumption.

    There is an asymptomatic period in ALS.

    “Obviously, there is an asymptomatic period in ALS, potentially bearing the risk that reported exposures occurred only after disease onset.”
7 of 7

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Counts of patients with multiple head injuries disagree

    Major

    The narrative reports 12 patients with multiple head/neck injuries. Table 2b places only four patients in the 2-3-injury column and one in the 4-5-injury column.

  • Head-injury counts conflict across the results

    Major

    The narrative says that 70 patients supplied head-injury information, comprising 48 without injury and 22 with injury. Table 3 instead lists 71 without injury and 21 with injury, accounting for all 92 patients.

  • Head-injury table total percentage does not match its fraction

    Minor

    The reported fraction 21/72 is 29.2%, rather than 30.0%.

    Reported 30 · recomputed 29.166667

  • Ice hockey percentage is incorrect

    Minor

    Table 2 lists five ice hockey players among 92 patients, which is 5.4%, not 9.8%. The subgroup analysis also reports 5/92 as 5.4%.

    Reported 9.8 · recomputed 5.434783

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. SUVA Medical, 2014, Versicherungsmedizin—Arbeitsmedizin—Rehabilitation

Cited by

Sorted by citations

Related

Authors
Feddermann‐Demont, N., Junge, A., Weber, K. P., Weller, M., Dvořák, J., & Tarnutzer, A. A.
Affiliations
  • University of Zurich (CH)
  • Fédération Internationale de Football Association (CH)
Corresponding author
Tarnutzer, Alexander A.
ORCID
Venue
Brain and Behavior
Publisher
Wiley
Published
2017-03-16
Volume
7
Issue
4
Pages
e00630-e00630
ISSN
  • 2157-9032 (ISSN-L)
  • 2162-3279
DOI
10.1002/brb3.630
PMC
PMC5390828
OpenAlex
W2596495043
Semantic Scholar
832b42f317650b0dc29d99f17e8cac71891ebbf1
Cited by
29
References
38
Citations by year
2026: 1 · 2025: 4 · 2024: 1 · 2023: 1 · 2022: 5 · 2021: 3 · 2020: 3 · 2019: 5 · 2018: 5 · 2017: 1
FWCI
2.29
Type
journal article
Language
en
Open access
Licence
Locations
  • Brain and Behavior (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Zurich Open Repository and Archive (University of Zurich) (acceptedVersion, cc-by)
  • PubMed Central (submittedVersion, cc-by)
  • Zurich Open Repository and Archive (University of Zurich) (submittedVersion, cc-by)
  • Zurich Open Repository and Archive (University of Zurich)
Funders
Fédération Internationale de Football Association (FIFA)
Topics
  • Health Sciences › Medicine › Neurology › Amyotrophic Lateral Sclerosis Research
  • Health Sciences › Medicine › Epidemiology › Traumatic Brain Injury Research
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Spinal Cord Injury Research
Keywords
amyotrophic lateral sclerosis, sports participation, physical activity, head trauma, traumatic brain injury, age at symptom onset, football, ice hockey, metabolic equivalents, analgesic use, pesticide exposure, extrinsic risk factors, neurodegeneration
MeSH terms
Amyotrophic Lateral Sclerosis, Athletic Injuries, Female, Craniocerebral Trauma, Humans, Male, Middle Aged, Surveys and Questionnaires, Retrospective Studies, Risk Factors, Sex Factors, Sports, Prevalence, Age of Onset, Neck Injuries

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-18.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-18.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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