Presymptomatic geographical distribution of ALS patients suggests the involvement of environmental factors in the disease pathogenesis.

BACKGROUND: Given that the pathogenetic process of ALS begins many years prior to its clinical onset, examining patients' residential histories may offer insights on the disease risk factors. Here, we analyzed the spatial distribution of a large ALS cohort in the 50 years preceding the disease onset. METHODS: Data from the PARALS register were used. A spatial cluster analysis was performed at the time of disease onset and at 1-year intervals up to 50 years prior to that. RESULTS: A total of 1124 patients were included. The analysis revealed a higher-incidence cluster in a large area (435,000 inhabitants) west of Turin. From 9 to 2 years before their onset, 105 cases were expected and 150 were observed, resulting in a relative risk of 1.49 (P = 0.04). We also found a surprising high number of patients pairs (51) and trios (3) who lived in the same dwelling while not being related. Noticeably, these occurrences were not observed in large dwellings as we would have expected. The probability of this occurring in smaller buildings only by chance was very low (P = 0.01 and P = 0.04 for pairs and trios, respectively). CONCLUSIONS: We identified a higher-incidence ALS cluster in the years preceding the disease onset. The cluster area being densely populated, many exposures could have contributed to the high incidence ALS cluster, while we could not find a shared exposure among the dwellings where multiple patients had lived. However, these findings support that exogenous factors are likely involved in the ALS pathogenesis.

Plateaus in amyotrophic lateral sclerosis progression: results from a population-based cohort.

BACKGROUND AND PURPOSE: The aim was to assess the frequency of plateaus in amyotrophic lateral sclerosis (ALS) progression using a large population-based cohort. METHODS: Data from the Piemonte and Valle d'Aosta ALS register were used. Patients who were diagnosed between 2007 and 2014 were considered. The follow-up period was extended until 31 December 2018. Visits after tracheostomy were excluded. A plateau was defined as a stable Amyotrophic Lateral Sclerosis Functional Rating Scale revised (ALSFRSr) score lasting at least 6, 12 or 18 months. RESULTS: Out of 1214 patients, 200 (16.5%), 93 (7.7%) and 52 (4.3%) showed at least one plateau lasting a minimum of 6, 12 and 18 months, respectively. Plateaus occurred mostly at high ALSFRSr scores and were more frequent during the initial phases of the disease course. Spinal onset [odds ratio (OR) 1.83, 95% confidence interval (CI) 1.16-2.95, P value 0.01) and predominant upper motor neuron phenotype (OR 2.18, 95% CI 1.36-3.48, P value 0.001) conferred a higher risk for the subsequent appearance of plateaus; conversely, older age at diagnosis (OR 0.25, 95% CI 0.11-0.54, P value 0.002 for >75 year age class) reduced this risk. CONCLUSIONS: Plateaus in ALS progression lasting at least 6 months appear in about one out of six patients and could last even 12, 18 months or more in a smaller subgroup of patients. Plateau occurrence should not lead the neurologist to automatically reconsider ALS diagnosis and should be considered for future clinical trial design.

Minimally invasive rehabilitation of the worn dentition: a case report utilising adhesive additive techniques and digital technologies.

The management of the worn dentition presents an increasing challenge that is encountered more frequently in daily dental practice. The consequences of tooth wear tend to be multifactorial and while they may initially only involve the loss of surface enamel it can progressively lead to significant destruction of the dentition. This paper discusses the management of a tooth wear case where a significant amount of tooth structure has been lost from both the anterior and posterior teeth. Protocols for assessment, treatment planning and restorative management of the tooth wear case are presented demonstrating the use of adhesive additive techniques and digital technologies to achieve functional and aesthetic rehabilitation of the dentition.

Correlation between Apolipoprotein E genotype and brain metabolism in amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: The aim of the study was to evaluate the metabolic correlates of Apolipoprotein E (APOE) genotype in amyotrophic lateral sclerosis (ALS) and to investigate the role of ε2 as a risk factor for cognitive impairment. METHODS: A total of 159 ALS cases underwent APOE and ALS-related genes analysis, neuropsychological assessment and cerebral 18 F-2-fluoro-2-deoxy-D-glucose positron emission tomography. The APOE genotype was regressed against whole brain metabolism as assessed by 18 F-2-fluoro-2-deoxy-D-glucose positron emission tomography, with age, sex, education, type of onset and C9orf72 status as covariates. RESULTS: Brain metabolism was significantly positively correlated with APOE genotype from ε2/ε2 to ε3/ε4 in the left prefrontal [Brodmann area (BA) 10], orbitofrontal (BAs 11, 45, 47) and anterior cingulate (BA 32) cortices. There was a tendency to a relative hypometabolism going towards the ε2/ε2 extreme. CONCLUSIONS: We found a highly significant, relatively lower metabolism in association with the ε2 allele in extra-motor areas typically affected in frontotemporal dementia (left prefrontal, orbitofrontal and anterior cingulate cortices), strengthening the finding of a role of ε2 as a risk factor for cognitive impairment in ALS. Our data suggested a link between cholesterol homeostasis and neurodegeneration.

Cardiovascular diseases may play a negative role in the prognosis of amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: Only a few studies have considered the role of comorbidities in the prognosis of amyotrophic lateral sclerosis (ALS) and have provided conflicting results. METHODS: Our multicentre, retrospective study included patients diagnosed from 1 January 2009 to 31 December 2013 in 13 referral centres for ALS located in 10 Italian regions. Neurologists at these centres collected a detailed phenotypic profile and follow-up data until death in an electronic database. Comorbidities at diagnosis were recorded by main categories and single medical diagnosis, with the aim of investigating their role in ALS prognosis. RESULTS: A total of 2354 incident cases were collected, with a median survival time from onset to death/tracheostomy of 43 months. According to univariate analysis, together with well-known clinical prognostic factors (age at onset, diagnostic delay, site of onset, phenotype, Revised El Escorial Criteria and body mass index at diagnosis), the presence of dementia, hypertension, heart disease, chronic obstructive pulmonary disease, haematological and psychiatric diseases was associated with worse survival. In multivariate analysis, age at onset, diagnostic delay, phenotypes, body mass index at diagnosis, Revised El Escorial Criteria, dementia, hypertension, heart diseases (atrial fibrillation and heart failure) and haematological diseases (disorders of thrombosis and haemostasis) were independent prognostic factors of survival in ALS. CONCLUSIONS: Our large, multicentre study demonstrated that, together with the known clinical factors that are known to be prognostic for ALS survival, hypertension and heart diseases (i.e. atrial fibrillation and heart failure) as well as haematological diseases are independently associated with a shorter survival. Our findings suggest some mechanisms that are possibly involved in disease progression, giving new interesting clues that may be of value for clinical practice and ALS comorbidity management.

Spatial epidemiology of amyotrophic lateral sclerosis in Piedmont and Aosta Valley, Italy: a population-based cluster analysis.

BACKGROUND AND PURPOSE: The analysis of the spatial distribution of cases could give important cues on putative environmental causes of a disease. Our aim was to perform a spatial analysis of an amyotrophic lateral sclerosis (ALS) cohort from the Piedmont and Aosta Valley ALS register (PARALS) over a 20-year period. METHODS: The address at the moment of diagnosis was considered for each ALS case. Municipalities' and census divisions' resident populations during the 1995-2014 period were obtained. A cluster analysis was performed adopting both Moran's index and the Kulldorff spatial scan statistic. RESULTS: A total of 2702 ALS patients were identified. An address was retrieved for 2671 (99%) patients. Moran's index was -0.01 (P value 0.83), thus revealing no clusters. SaTScan identified no statistically significant clusters. When census divisions were considered, Moran's index was 0.13 (P value 0.45); SaTScan revealed one statistically significant small cluster in the province of Alessandria. Here, 0.0099 cases were expected and three cases were observed (relative risk 304.60; 95% confidence interval 109.83-845.88, P value 0.03). DISCUSSION: Our study showed a substantial homogeneous distribution of ALS cases in Piedmont and Aosta Valley. The population-based setting and the adoption of proper statistical analyses strengthen the validity of our results. Such a finding further suggests the involvement of multiple environmental and genetic factors in ALS pathogenesis.

The role of pre-morbid diabetes on developing amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: The literature on the association between diabetes and amyotrophic lateral sclerosis (ALS) consists of a limited number of studies. This cohort study was developed in order to assess the role of diabetes on the risk of developing ALS. METHODS: The study population was represented by all residents in Turin (Italy) at the beginning of 1996 who participated in the 1991 census, over 14 years of age (n = 727 977) and followed up for ALS occurrence from 1998 to 2014. Presence of diabetes at baseline or during follow-up was ascertained through two Piedmont regional sources: the Diabetes Registry and the Anatomical Therapeutic Chemical Drug Prescription Archive. The risk of ALS was estimated using the Piedmont and Valle d'Aosta ALS Registry (PARALS). The association of diabetes, treated as a time-dependent variable, with ALS onset was estimated through Cox proportional hazard regression models adjusted for age, gender, education and marital status. RESULTS: During follow-up, 397 subjects developed ALS, 24 of whom were already diabetic before ALS onset. Diabetes was associated with a significantly decreased risk of ALS [hazard ratio, 0.30 (95% confidence interval, 0.19-0.45)] without differences in risk by gender, age class or ALS phenotype. CONCLUSION: The results support the protective role of diabetes toward ALS.

Occupations and amyotrophic lateral sclerosis: are jobs exposed to the general public at higher risk?

Background: Aim of this study was to assess whether previous employment in certain occupations could be a risk factor for Amyotrophic Lateral Sclerosis (ALS) incidence. This topic has been explored by several studies, but no risk factor has been firmly identified. Methods: The study population consisted of all subjects over 30 years old resident in Turin in 1996 who worked or were unemployed at 1991 Italian census (n = 284 406), followed up for ALS occurrence from 1996 to 2014. The risk of ALS was estimated in relation to the occupation held in 1991, using the Italian classification of occupations at the greatest detail. The association between occupations and ALS risk was estimated through Huber-White sandwich multivariate Poisson regression models adjusted for age, gender, education and marital status. Results: During the follow-up, 208 subjects developed ALS. ALS risk was significantly associated with previous employment as bank teller (IRR = 7.33), general practitioner (IRR = 4.61) and sales representative (IRR = 3.06). Categorizing all occupations as exposed or unexposed to direct contact with general public, it was found that previous employment in this group of occupations increased significantly ALS risk (IRR = 1.51), mainly driven by occupations in direct contact with customers (IRR = 1.79). Conclusions: The study results indicate that ALS risk may be increased by previous employment in occupations implying direct contact with the general public, in particular customers. A possible explanation of this finding, partly supported by the literature, is that workers in contact with the public could be more exposed to certain infections, which would increase their ALS risk.

Specialist palliative care improves the quality of life in advanced neurodegenerative disorders: NE-PAL, a pilot randomised controlled study.

BACKGROUND: This study analysed the impact on palliative care outcomes of a new specialist palliative care service for patients severely affected by amyotrophic lateral sclerosis (ALS/MND), multiple sclerosis, Parkinson's disease and related disorders (multiple system atrophy progressive supranuclear palsy, MSA-PSP). METHODS: The design followed the Medical Research Council Framework for the evaluation of complex interventions. A phase II randomised controlled trial (RCT) was undertaken comparing an immediate referral to the service (FT, fast track) to a 16-week wait (standard track (ST), standard best practice) using a parallel arm design. The main outcome measures were Quality of Life (measured with Schedule for the Evaluation of Individual Quality of Life Direct Weight, SEIQoL-DW) and burden of the carers (Caregivers Burden Inventory, CBI), with secondary outcomes of symptoms, psychosocial and spiritual issues. RESULTS: 50 patients severely affected by neurodegenerative conditions and their informal family carers were randomised: 25 FT, 25 ST. At baseline (T0), there were no differences between groups. 4 patients died during the follow-up (2 FT, 2 ST) and 2 FT patients dropped out before the end of the study. After 16 weeks (T1), FT participants scored significant improvement in the SEIQoL-DW index, pain dyspnoea sleep disturbance and bowel symptoms. CONCLUSIONS: This exploratory RCT provides evidence that no harm was experienced by SPCS for patients severely affected by neurodegenerative disorders. There was an improvement in quality of life and physical symptoms for neurological patients in palliative care. Caregiver burden was not affected by the service.

Monocytes of patients with amyotrophic lateral sclerosis linked to gene mutations display altered TDP-43 subcellular distribution.

AIMS: Cytoplasmic accumulation of the nuclear protein transactive response DNA-binding protein 43 (TDP-43) is an early determinant of motor neuron degeneration in most amyotrophic lateral sclerosis (ALS) cases. We previously disclosed this accumulation in circulating lymphomonocytes (CLM) of ALS patients with mutant TARDBP, the TDP-43-coding gene, as well as of a healthy individual carrying the parental TARDBP mutation. Here, we investigate TDP-43 subcellular localization in CLM and in the constituent cells, lymphocytes and monocytes, of patients with various ALS-linked mutant genes. METHODS: TDP-43 subcellular localization was analysed with western immunoblotting and immunocytofluorescence in CLM of healthy controls (n = 10), patients with mutant TARDBP (n = 4, 1 homozygous), valosin-containing protein (VCP; n = 2), fused in sarcoma/translocated in liposarcoma (FUS; n = 2), Cu/Zn superoxide dismutase 1 (SOD1; n = 6), chromosome 9 open reading frame 72 (C9ORF72; n = 4), without mutations (n = 5) and neurologically unaffected subjects with mutant TARDBP (n = 2). RESULTS: TDP-43 cytoplasmic accumulation was found (P < 0.05 vs. controls) in CLM of patients with mutant TARDBP or VCP, but not FUS, in line with TDP-43 subcellular localization described for motor neurons of corresponding groups. Accumulation also characterized CLM of the healthy individuals with mutant TARDBP and of some patients with mutant SOD1 or C9ORF72. In 5 patients, belonging to categories described to carry TDP-43 mislocalization in motor neurons (3 C9ORF72, 1 TARDBP and 1 without mutations), TDP-43 cytoplasmic accumulation was not detected in CLM or in lymphocytes but was in monocytes. CONCLUSIONS: In ALS forms characterized by TDP-43 mislocalization in motor neurons, monocytes display this alteration, even when not manifest in CLM. Monocytes may be used to support diagnosis, as well as to identify subjects at risk, of ALS and to develop/monitor targeted treatments.

NADPH oxidase 2 (NOX2) enzyme activation in patients with chronic inflammatory demyelinating polyneuropathy.

BACKGROUND AND PURPOSE: Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired immunomediated condition affecting the peripheral nervous system where probably macrophages are the primary effector cells for demyelination. Reactive oxygen species (ROS), catalyzed by the NOX family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzymes, can induce peroxidation and are potentially injurious to myelin. Our aim was to assess the activity of NOX2, an isoform of NOX, in a series of CIDP patients and to analyze the effect of intravenous immunoglobulin (IVIg) on NOX2. METHODS: Thirty CIDP patients treated with IVIg and 30 control subjects were enrolled. To evaluate NOX2 activity, neutrophil and monocyte oxidative burst was measured directly in fresh whole blood using the Phagoburst™ assay, a fluorescence-activated cell sorting method. The mean fluorescence intensity, emitted in response to different stimuli, leads to the production of ROS and corresponds to the percentage of oxidizing cells and their enzymatic activity. RESULTS: Mean fluorescence intensity values for granulocyte and monocyte burst in patients (mean 633.3, SD 191; mean 111.8, SD 28.5) were different from those measured in healthy controls (granulocytes, mean 436.6, SD 137.0, P = 0.0003; monocytes, mean 78.2, SD 17.3, P = 0.000001). Moreover, IVIg administration increased both granulocyte (P = 0.005) and monocyte (P = 0.0009) burst. CONCLUSION: Our findings demonstrate that oxidative burst is significantly increased in CIDP patients and that treatment with IVIg enhances oxidative values, thus representing a possible IVIg therapeutic effect linked to a regulatory effect of ROS. Based on this, the development of treatments targeting the specific activation of NOX may be beneficial in autoimmune disorders.

Global epidemiology of amyotrophic lateral sclerosis: a systematic review of the published literature.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is relatively rare, yet the economic and social burden is substantial. Having accurate incidence and prevalence estimates would facilitate efficient allocation of healthcare resources. OBJECTIVE: To provide a comprehensive and critical review of the epidemiological literature on ALS. METHODS: MEDLINE and EMBASE (1995-2011) databases of population-based studies on ALS incidence and prevalence reporting quantitative data were analyzed. Data extracted included study location and time, design and data sources, case ascertainment methods and incidence and/or prevalence rates. Medians and interquartile ranges (IQRs) were calculated, and ALS case estimates were derived using 2010 population estimates. RESULTS: In all, 37 articles met the inclusion criteria. In Europe, the median incidence rate (/100,000 population) was 2.08 (IQR 1.47-2.43), corresponding to an estimated 15,355 (10,852-17,938) cases. Median prevalence (/100,000 population) was 5.40 (IQR 4.06-7.89), or 39,863 (29,971-58,244) prevalent cases. CONCLUSIONS: Disparity in rates among ALS incidence and prevalence studies may be due to differences in study design or true variations in population demographics such as age and geography, including environmental factors and genetic predisposition. Additional large-scale studies that use standardized case ascertainment methods are needed to more accurately assess the true global burden of ALS.

Trauma and amyotrophic lateral sclerosis: a case-control study from a population-based registry.

BACKGROUND AND PURPOSE: Published reports on the association between amyotrophic lateral sclerosis (ALS) and trauma are controversial suggesting the need for a new case-control study done in a large population. METHODS: A case-control study was undertaken in Italy to assess this association. Cases were patients with newly diagnosed ALS from four population-based registries. For each case, two hospital controls were selected, matched for age, sex, and province of residence, one with a neurological (non-degenerative) disease and one with a non-neurological disease (other than orthopedic or surgical). Traumatic events (defined as accidental events causing injuries requiring medical care) were recorded with details on type, site, timing, severity, and complications. The risks were assessed as odds ratios (ORs) with 95% confidence intervals (CI), crude and adjusted for age, sex, education, interviewee (patient or surrogate), physical activity, smoking, alcohol, and coffee. RESULTS: The study population comprised 377 patients in each of the three groups. One or more traumatic events were reported by 225 cases (59.7%), 191 neurological controls (50.7%), and 179 non-neurological controls (47.5%) (P < 0.01) (OR 1.63; 95% CI 1.25-2.14) (P < 0.01). The ORs were 3.07 (95% CI 1.86-5.05) for patients reporting 3+ traumatic events and 2.44 (95% CI 1.36-4.40) for severe traumatic events. The ORs remained significant when the analysis was limited to events that occurred 5+ and 10+ years before ALS onset, to incident ALS, and direct informant. CONCLUSION: Antecedent trauma, repeated trauma, and severe trauma may be risk factors for ALS.

Neurobehavioral dysfunction in ALS has a negative effect on outcome and use of PEG and NIV.

OBJECTIVE: To assess the effect of neurobehavioral dysfunction on amyotrophic lateral sclerosis (ALS) survival and on the use of life-prolonging therapies in a population-based setting. METHODS: Of the 132 patients diagnosed with ALS in the province of Torino, Italy, between January 1, 2007, and June 30, 2008, 128 participated in the study. Neurobehavioral dysfunction was assessed with the Frontal Systems Behavior Scale (FrSBe), using the Family Rating forms, administered within 4 months from diagnosis. RESULTS: The 128 patients included 71 men and 57 women, with a mean age at onset of 64.7 (SD 11) years. Forty-one patients (32.0%) had a neurobehavioral dysfunction and 9 (7.0%) an isolated dysexecutive behavior. Enteral nutrition (EN) and noninvasive ventilation (NIV) were performed with similar frequencies in patients with and without neurobehavioral dysfunction. Patients with neurobehavioral dysfunction had a significantly shorter survival than those with a normal FrSBe score (median survival, 3.3 vs 4.3 years; p = 0.02). Patients with isolated dysexecutive behavior had a shorter survival than those without neurobehavioral dysfunction (median survival, 2.5 vs 4.5 years; p = 0.03). Patients with neurobehavioral dysfunction had a shorter survival after EN and NIV, while patients with isolated dysexecutive behavior had a shorter survival after NIV but not after EN. The negative effect of comorbid neurobehavioral dysfunction and of isolated dysexecutive behavior on survival persisted under the Cox multivariate model. CONCLUSIONS: The presence of neurobehavioral dysfunction or of isolate dysexecutive behavior in ALS at diagnosis is a strong predictor of a poor outcome, partially related to a reduced efficacy of life-prolonging therapies.

Pain in amyotrophic lateral sclerosis: a population-based controlled study.

BACKGROUND AND PURPOSE: To assess the prevalence and characteristics of pain in an epidemiological series of patients with amyotrophic lateral sclerosis (ALS) compared to population-based controls. METHODS: Of the 183 patients with ALS resident in the province of Torino, Italy, 160 accepted to be interviewed. Controls were randomly selected from the lists of general practitioners. Pain was assessed using the Brief Pain Inventory. RESULTS: Patients with ALS reported pain more frequently than controls [91 (56.9%) vs. 53 (33.1%); P = 0.001]. Pain frequency and intensity were correlated with a worse functional score and a longer disease duration. In patients with ALS, pain was more frequently located at the extremities (P = 0.006). Pain interfered with all areas of daily function, but patients reported a greater interference than controls in the domains of enjoyment of life and relation with other people. Sixty-four patients (70.3% of those with pain) and 24 controls (45.3% of those with pain) (P = 0.003) were treated for pain, most frequently with non-steroidal anti-inflammatory drugs. ALS cases were also more frequently prescribed non-opioid analgesics and opioids than controls. CONCLUSIONS: Our study indicates that pain is frequent in all stages of ALS, but that it often goes underrecognized and undertreated. It is significantly more frequent in patients with ALS than in population-based controls. Future studies need to clarify the mechanisms of pain in ALS and determine the most effective treatment strategy.

A distinct MR imaging phenotype in amyotrophic lateral sclerosis: correlation between T1 magnetization transfer contrast hyperintensity along the corticospinal tract and diffusion tensor imaging analysis.

BACKGROUND AND PURPOSE: In the search for a diagnostic marker in ALS, we focused our attention on the hyperintense signal intensity in T1 MTC MR images along the CST, detected in some patients and not found in other patients with ALS and in control subjects. The aim of this study was to investigate the relationship between the hyperintense signal intensity in T1 MTC images and white matter damage. To this purpose, we studied potential heterogeneities in DTI values within our patients by using TBSS without a priori anatomic information. MATERIALS AND METHODS: In 43 patients with ALS and 43 healthy control subjects, the presence or absence of T1 MTC hyperintense signal intensity was evaluated. With a DTI analysis with a TBSS approach, differences in FA distribution between the 2 groups (patients with T1 MTC hyperintense signal intensity and patients without it) compared with each other and with control subjects were investigated. RESULTS: We found regional differences in white matter FA between patients with T1 MTC hyperintense signal intensity (37.2%) and patients without it. Patients with T1 MTC abnormal signal intensity showed lower FA strictly limited to the motor network and the posterior aspect of the body of the CC without extramotor FA reductions, whereas patients without this sign showed FA reductions in several confluent regions within and outside the CST and in the whole CC. CONCLUSIONS: T1 MTC hyperintense signal intensity in the CST and posterior CC, when present, is specific for ALS and represents, among patients with ALS, a possible distinct phenotype of presentation of the disease with prominent UMN involvement.

ALS clinical trials: do enrolled patients accurately represent the ALS population?

OBJECTIVE: To assess the effect of eligibility criteria in amyotrophic lateral sclerosis (ALS) clinical trials on the representativeness of the enrolled population. METHODS: Patients enrolled in 8 placebo-controlled clinical trials in our ALS center from 2003 to 2008 were compared 1) to the patients included a prospective epidemiologic register (Piemonte and Valle d'Aosta register for ALS, PARALS) in the same period and 2) the subset of PARALS patients who met the usual criteria for inclusion in clinical trials (PARALS-ct) (definite, probable, probable laboratory-supported ALS; age between 18 and 75 years; disease duration <36 months; vital capacity at diagnosis ≥70%; score ≥3 at the items swallowing and respiratory insufficiency at the Amyotrophic Lateral Sclerosis Functional Rating Scale-revised scale; riluzole therapy). RESULTS: A total of 164 patients were enrolled in 8 different clinical trials. The PARALS cohort included 813 patients, of whom 539 (66.3%) met the entry criteria for clinical trials. Patients enrolled in clinical trials were different from both epidemiologic cohorts, since they were younger, had a longer diagnostic delay, and were more likely to have a spinal onset, and to be men. Tracheostomy-free survival was significantly longer in the group of patients enrolled in clinical trials (median survival time, trial patients, 3.9 years [95% confidence interval (CI) 3.4-4.4]; PARALS, 2.6 [2.4-2.8]; PARALS-ct, 2.9 [2.7-3.1]). CONCLUSIONS: Patients enrolled in clinical trials do not satisfactorily represent the ALS population; consequently, the findings of ALS trials lack of external validity (generalizability). Efforts should be made to improve patients' recruitment in trials, particularly enrolling incident rather than prevalent cases.