Incidence of motor neuron disease/amyotrophic lateral sclerosis in South Africa: a 4-year prospective study

Sex biology in amyotrophic lateral sclerosis

Although sex differences in amyotrophic lateral sclerosis (ALS) have not been studied systematically, numerous clinical and preclinical studies have shown sex to be influential in disease prognosis. Moreover, with the development of advanced imaging tools, the difference between male and female brain in structure and function and their response to neurodegeneration are more definitive. As discussed in this review, ALS patients exhibit a sex bias pertaining to the features of the disease, and their clinical, pathological, (and pathophysiological) phenotypes. Several epidemiological studies have indicated that this sex disparity stems from various aetiologies, including sex-specific brain structure and neural functioning, genetic predisposition, age, gonadal hormones, susceptibility to traumatic brain injury (TBI)/head trauma and lifestyle factors.

Global Prevalence and Incidence of Amyotrophic Lateral Sclerosis: A Systematic Review

BACKGROUND AND OBJECTIVES

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disorder affecting upper and lower motor neurons. Due to its rarity and rapidly progressive nature, studying the epidemiology of ALS is challenging, and a comprehensive picture of the global burden of this disease is lacking. The objective of this systematic review was to describe the global incidence and prevalence of ALS.

METHODS

We searched MEDLINE, Embase, Global Health, PsycInfo, Cochrane Library, and CINAHL to identify articles published between January 1, 2010, and May 6, 2021. Studies that were population based and reported estimates of prevalence, incidence, and/or mortality of ALS were eligible for inclusion. This study focuses on the incidence and prevalence. Quality assessment was performed using a tool developed to evaluate methodology relevant to prevalence and incidence studies. This review was registered with PROSPERO, CRD42021250559.

RESULTS

This search generated 6,238 articles, of which 140 were selected for data extraction and quality assessment. Of these, 85 articles reported on the incidence and 61 on the prevalence of ALS. Incidence ranged from 0.26 per 100,000 person-years in Ecuador to 23.46 per 100,000 person-years in Japan. Point prevalence ranged from 1.57 per 100,000 in Iran to 11.80 per 100,000 in the United States. Many articles identified cases with ALS from multiple data sources.

DISCUSSION

There is variation in reported incidence and prevalence estimates of ALS across the world. While registries are an important and powerful tool to quantify disease burden, such resources are not available everywhere. This results in gaps in reporting of the global epidemiology of ALS, as highlighted by the degree of variation (and quality) in estimates of incidence and prevalence reported in this review.

Motor neuron disease in black African patients at a tertiary care hospital in Soweto, South Africa

INTRODUCTION

In this brief report, we describe the nature of ALS in a South African cohort of patients of Black African ancestry - a population which has been historically understudied.

METHODS

We performed a chart review of all patients attending the ALS/MND clinic at the Chris Hani Baragwanath Academic Hospital in Soweto, Johannesburg, South Africa, during the period 1 January 2015 to 30 June 2020. Cross-sectional demographic and clinical data captured at the time of diagnosis was collected.

RESULTS

Seventy-one patients were included in the study. Males constituted 66% (n = 47), with a male to female sex ratio of 2:1. The median age at onset of symptoms was 46 years (IQR 40-57) with a median disease duration at diagnosis (diagnostic delay) of 2 years (IQR 1-3). The onset was spinal in 76% and bulbar in 23%. The median ALSFRS-R score at time of presentation was 29 (IQR 23-38.5). The median ALSFRS-R slope (unit/month) was 0.80 (IQR 0.43-1.39). Sixty five patients (92%) were diagnosed with the classic ALS phenotype. Fourteen patients were known to be HIV positive, and of those, 12 were on antiretroviral treatment (ART). None of the patients had familial ALS.

CONCLUSION

Our findings of an earlier age at symptom onset and seemingly advanced disease at presentation in patients with Black African ancestry support the existing literature on the African population.

Epidemiology of amyotrophic lateral sclerosis in the north east Tuscany in the 2018–2021 period

Background

The incidence of Amyotrophic Lateral Sclerosis (ALS) varies among different geographical areas and seems to increase over time. This study aimed to examine the epidemiologic data of ALS in the north-east Tuscany and compare the results with those of similar surveys.

Methods

Data from ALS cases diagnosed in Florence and Prato Hospitals were prospectively collected from 1st June 2018 to 31st May 2021.

Results

The age- and sex-adjusted incidence rate of ALS in cases per 100,000 population was 2.71 (M/F ratio: 1.21), significantly higher as compared to that reported in the 1967-1976 decade in the same geographical area (0.714). The age- and sex-adjusted incidence rate among resident strangers was similar to that of the general population (2.69). A slightly higher incidence rate (4.36) was observed in the north-east area of Florence province, which includes the Mugello valley. The mean prevalence was of 7.17/100,00. The mean age at diagnosis was 69.7 years, with a peak between 70 and 79 years among men and a smoother age curve among women.

Conclusions

ALS epidemiological features in north-east Tuscany are in line with other Italian and European Centers. The dramatic increase of the local disease burden over the last decades probably reflects better ascertainment methods and health system.

Sex and gender differences in Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis: a narrative review

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), exhibit high phenotypic variability and they are very common in the general population. These diseases are associated with poor prognosis and a significant burden on patients and their caregivers. Although increasing evidence suggests that biological sex is an important factor for the development and phenotypical expression of some NDs, the role of sex and gender in the diagnosis and prognosis of NDs has been poorly explored. Current knowledge relating to sex- and gender-related differences in the epidemiology, clinical features, biomarkers, and treatment of AD, PD, and ALS will be summarized in this narrative review. The cumulative evidence hitherto collected suggests that sex and gender are factors to be considered in explaining the heterogeneity of these NDs. Clarifying the role of sex and gender in AD, PD, and ALS is a key topic in precision medicine, which will facilitate sex-specific prevention and treatment strategies to be implemented in the near future.

Age of Onset and Length of Survival of Queensland Patients with Amyotrophic Lateral Sclerosis: Details of Subjects with Early Onset and Subjects with Long Survival

INTRODUCTION

The aims of the study were to document the characteristics of amyotrophic lateral sclerosis (ALS) patients in Queensland, to examine factors influencing age of onset, and survival, and to study those with early-onset (<45 years) disease and those with long (>5 years) survival.

METHODS

We studied subjects seen at the ALS Clinic at the Royal Brisbane and Women's Hospital. We recorded sex, age of onset, region of onset, length of survival, presence of family history, type of disease, and evidence of cognitive involvement. We analysed the influence of these features on age of onset and survival. We analysed the features of patients with early onset of disease and patients with long survival.

RESULTS

There were 855 ALS patients (505 males) in the cohort. The age of onset was lower in males than females, in patients with a family history of ALS compared to those without, and in patients with spinal onset compared to bulbar onset. Early-onset disease was seen in 10% of patients, and had a greater proportion of males, spinal onset, and classical ALS phenotype compared to late-onset disease. Survival was shorter in females, in patients with bulbar onset, and in patients with classical ALS. Long survival was seen in 18% of patients. Patients with long survival had younger age of onset, greater proportion of males, spinal onset, and fewer patients with classical ALS.

CONCLUSION

Our study confirms that ALS is more prevalent in males and that spinal onset is more common than bulbar onset. Males have earlier onset but longer survival. We found that overall, patients with classical ALS have worse survival than ALS variants, but some patients who were considered to have classical ALS had long survival. This study confirms the similarity of ALS in our region to ALS in other geographical regions.

Amyotrophic lateral sclerosis mortality rates in Latin America and the Caribbean: a meta-analysis

Background: Recent studies have described a low occurrence of Amyotrophic Lateral Sclerosis (ALS) in Latin America. Significant differences in ALS risk have been reported among ethnic populations in the region. We conducted a meta-analysis using population-based data to describe ALS mortality rates in Latin America. We explored sources of heterogeneity among key covariates.Methods: National mortality registries from Latin American countries were searched to identify ALS deaths according to the International Classification of Diseases (ICD-9: code 335.2 and ICD-10: code G12.2). Crude and standardized mortality rates were calculated. A random-effect meta-analysis was conducted to estimate pooled mortality rates. Subgroup analysis was performed as a means of investigating heterogeneity.Results: Overall, 28,548 ALS deaths and 819 million person-years of follow-up (PYFU) from ten Latin American countries were considered. Standardized mortality varied among countries. The highest mortality rates were observed in Uruguay and Costa Rica at 1.3 and 1.2 per 100,000 PYFU, respectively. The pooled crude mortality rate was 0.38 (95%CI: 0.28-0.53) and the pooled standardized mortality was 0.62 (95%CI: 0.49-0.77) per 100,000 PYFU. Heterogeneity was high (I2: 99.9%, Cochran's Q p < 0.001). Subgroup analysis showed a higher mortality rate among countries with a higher proportion of Caucasian populations and higher income levels.Conclusion: There is a lower ALS occurrence in Latin America compared to Europe and North America. This meta-analysis supports the hypothesis of a higher ALS risk among the Caucasian population. Further studies are needed to investigate the role of ancestral origins in ALS, taking socioeconomic status into consideration.

Adaptation and norming of the Edinburgh Cognitive and behavioural amyotrophic lateral sclerosis screen (ECAS) for three language groups in South Africa

Objectives: To adapt and translate the Edinburgh Cognitive and behavioural amyotrophic lateral sclerosis screen (ECAS); to generate preliminary normative data for three language groups in South Africa (SA); to assess the convergent validity of the ECAS in SA samples. Methods: The ECAS was linguistically and culturally adapted for Afrikaans-, isiXhosa-, and English-speaking SA adults (n = 108, 100, and 53, respectively). Each language group was stratified by age and educational level. Cutoff scores for cognitive impairment were set at the group mean minus two standard deviations (SDs). A pilot sample of ALS patients and controls (n = 21 each) were administered the ECAS and an extensive neuropsychological evaluation (NPE) and the Montreal Cognitive Assessment (MoCA) to assess convergent validity. Results: Across the three language groups, the total ECAS cutoff scores ranged from 68 to 97. The ECAS score correlated significantly positively with educational level (p < 0.001) and negatively with age (p < 0.005). The restricted letter fluency task demonstrated a floor effect, particularly in Afrikaans-speakers. The mean total ECAS score (±SD) was similar in ALS patients (103.52 ± 11.90) and controls (100.67 ± 20.49; p = 0.58). Three (14.3%) ALS patients scored below the cutoff for cognitive impairment. Correlations between individual ECAS subtests and analogous NPE tests ranged from weak to moderate. The MoCA score was significantly positively correlated with the ECAS total score (r = 0.59; p = < 0.001). Conclusions: The adapted ECAS and associated normative data will aid cognitive screening of African ALS patients. Larger participant numbers are needed to assess the validity of the adapted instrument.

Analysis of incidence of motor neuron disease in England 1998-2019: use of three linked datasets

Objective: This study uses three linked datasets to provide an estimate of incidence of motor neuron disease (MND) in England from 1998 to 2019. Comparison is made to previous British studies. It examines age at diagnosis and ethnicity of those affected.

Methods: The literature was searched for studies of MND incidence in Great Britain from 1995 to date. The QResearch and linked Hospital Episode Statistics and Death register databases were searched from 1998 to 2019 for cases of MND, and incidence calculated from 16.8 million adults and 112 million adult years of data.

Results: We found 6437 adults with a diagnosis of MND giving an incidence of MND of 5.69/100,000 person years (95% CI 5.51–5.88); 6.57 (6.41–6.99) in men and 4.72 (4.49–4.97) in women when age-standardized to the 2011 UK population. The median age of diagnosis was 72 years. Peak incidence occurred in the 80–84 year age group in men and 75–79 in women. Age-standardized incidence was as high in Bangladeshi, Black Caribbean, Indian, other Asian and Pakistani people as in White people. Black African and Chinese people had a lower incidence.

Conclusion: The use of three linked national datasets captured 33% more people than a primary care dataset alone. Patients were older than in previous studies and rates were high in all ethnic groups studied except Black African and Chinese people. We present the highest incidence of MND reported globally in the past 50 years. Methodological differences may in part explain differences with previous reports. The use of national datasets may have captured additional MND patients with serious comorbidities who have not seen a neurologist before death. A limitation of this approach is that unlike population registers, which minimize false positive diagnosis by neurologist review of each patient, we cannot review diagnosis for individuals as data are anonymized.

Revealing the Mutational Spectrum in Southern Africans With Amyotrophic Lateral Sclerosis

Background and Objectives

To perform the first screen of 44 amyotrophic lateral sclerosis (ALS) genes in a cohort of African genetic ancestry individuals with ALS using whole-genome sequencing (WGS) data.

Methods

One hundred three consecutive cases with probable/definite ALS (using the revised El Escorial criteria), and self-categorized as African genetic ancestry, underwent WGS using various Illumina platforms. As population controls, 238 samples from various African WGS data sets were included. Our analysis was restricted to 44 ALS genes, which were curated for rare sequence variants and classified according to the American College of Medical Genetics guidelines as likely benign, uncertain significance, likely pathogenic, or pathogenic variants.

Results

Thirteen percent of 103 ALS cases harbored pathogenic variants; 5 different SOD1 variants (N87S, G94D, I114T, L145S, and L145F) in 5 individuals (5%, 1 familial case), pathogenic C9orf72 repeat expansions in 7 individuals (7%, 1 familial case) and a likely pathogenic ANXA11 (G38R) variant in 1 individual. Thirty individuals (29%) harbored ≥1 variant of uncertain significance; 10 of these variants had limited pathogenic evidence, although this was insufficient to permit confident classification as pathogenic.

Discussion

Our findings show that known ALS genes can be expected to identify a genetic cause of disease in >11% of sporadic ALS cases of African genetic ancestry. Similar to European cohorts, the 2 most frequent genes harboring pathogenic variants in this population group are C9orf72 and SOD1.

The Interplay Between Neuroinfections, the Immune System and Neurological Disorders: A Focus on Africa

Neurological disorders related to neuroinfections are highly prevalent in Sub-Saharan Africa (SSA), constituting a major cause of disability and economic burden for patients and society. These include epilepsy, dementia, motor neuron diseases, headache disorders, sleep disorders, and peripheral neuropathy. The highest prevalence of human immunodeficiency virus (HIV) is in SSA. Consequently, there is a high prevalence of neurological disorders associated with HIV infection such as HIV-associated neurocognitive disorders, motor disorders, chronic headaches, and peripheral neuropathy in the region. The pathogenesis of these neurological disorders involves the direct role of the virus, some antiretroviral treatments, and the dysregulated immune system. Furthermore, the high prevalence of epilepsy in SSA (mainly due to perinatal causes) is exacerbated by infections such as toxoplasmosis, neurocysticercosis, onchocerciasis, malaria, bacterial meningitis, tuberculosis, and the immune reactions they elicit. Sleep disorders are another common problem in the region and have been associated with infectious diseases such as human African trypanosomiasis and HIV and involve the activation of the immune system. While most headache disorders are due to benign primary headaches, some secondary headaches are caused by infections (meningitis, encephalitis, brain abscess). HIV and neurosyphilis, both common in SSA, can trigger long-standing immune activation in the central nervous system (CNS) potentially resulting in dementia. Despite the progress achieved in preventing diseases from the poliovirus and retroviruses, these microbes may cause motor neuron diseases in SSA. The immune mechanisms involved in these neurological disorders include increased cytokine levels, immune cells infiltration into the CNS, and autoantibodies. This review focuses on the major neurological disorders relevant to Africa and neuroinfections highly prevalent in SSA, describes the interplay between neuroinfections, immune system, neuroinflammation, and neurological disorders, and how understanding this can be exploited for the development of novel diagnostics and therapeutics for improved patient care.

Local ancestry prediction with PyLAE

Summary

We developed PyLAE, a new tool for determining local ancestry along a genome using whole-genome sequencing data or high-density genotyping experiments. PyLAE can process an arbitrarily large number of ancestral populations (with or without an informative prior). Since PyLAE does not involve estimating many parameters, it can process thousands of genomes within a day. PyLAE can run on phased or unphased genomic data. We have shown how PyLAE can be applied to the identification of differentially enriched pathways between populations. The local ancestry approach results in higher enrichment scores compared to whole-genome approaches. We benchmarked PyLAE using the 1000 Genomes dataset, comparing the aggregated predictions with the global admixture results and the current gold standard program RFMix. Computational efficiency, minimal requirements for data pre-processing, straightforward presentation of results, and ease of installation make PyLAE a valuable tool to study admixed populations.

Availability and implementation

The source code and installation manual are available at https://github.com/smetam/pylae.

Repeats expansions in ATXN2, NOP56, NIPA1 and ATXN1 are not associated with ALS in Africans

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized primarily by progressive loss of motor neurons. Although ALS occurs worldwide and the frequency and spectrum of identifiable genetic causes of disease varies across populations, very few studies have included African subjects. In addition to a hexanucleotide repeat expansion (RE) in C9orf72, the most common genetic cause of ALS in Europeans, REs in ATXN2, NIPA1 and ATXN1 have shown variable associations with ALS in Europeans. Intermediate range expansions in some of these genes (e.g. ATXN2) have been reported as potential risk factors, or phenotypic modifiers, of ALS. Pathogenic expansions in NOP56 cause spinocerebellar ataxia-36, which can present with prominent motor neuron degeneration. Here we compare REs in these genes in a cohort of Africans with ALS and population controls using whole genome sequencing data. Targeting genotyping of short tandem repeats at known loci within ATXN2, NIPA1, ATXN1 and NOP56 was performed using ExpansionHunter software in 105 Southern African (SA) patients with ALS. African population controls were from an in-house SA population control database (n = 25), the SA Human Genome Program (n = 24), the Simons Genome Diversity Project (n = 39) and the Illumina Polaris Diversity Cohort (IPDC) dataset (n = 50). We found intermediate RE alleles in ATXN2 (27-33 repeats) and ATXN1 (33-35 repeats), and NIPA1 long alleles (≥8 repeats) were rare in Africans, and not associated with ALS (p > 0.17). NOP56 showed no expanded alleles in either ALS or controls. We also compared the differences in allele distributions between the African and n = 50 European controls (from the IPDC). There was a statistical significant difference in the distribution of the REs in the ATXN1 between African and European controls (Chi-test p < 0.001), and NIPA1 showed proportionately more longer alleles (RE > 8) in Europeans vs. Africans (Fisher's p = 0.016). The distribution of RE alleles in ATXN2 and NOP56 were similar amongst African and European controls. In conclusion, repeat expansions in ATXN2, NIPA1 and ATXN1, which showed associations with ALS in Europeans, were not replicated in Southern Africans with ALS.

Epidemiological and genetic features of amyotrophic lateral sclerosis in Latin America and the Caribbean: a systematic review

Introduction: Heterogeneity of amyotrophic lateral sclerosis (ALS) has been suggested in terms of epidemiology, phenotypes and genetics between geographic areas and populations. However, there is limited information in Latin America. We conducted a systematic review that aimed to describe the epidemiology, frequency of genetic mutations, clinical characteristics and survival of ALS patients in this region. Methods: We reviewed Medline, Scopus, Scielo and LILACS databases up to April 2020. The search terms "Amyotrophic Lateral Sclerosis" or "Motor Neuron Disease" were used in combination with the list of Latin American countries from the United Nations. All observational studies were included. A methodological overview was performed using the principles of descriptive epidemiology. Results: Overall, 1364 publications were identified and 36 studies were selected, covering 13 Latin American countries. According to the original reports, ALS occurrence varied among countries with a standardized incidence ranging from 0.3 per 100,000 person-years follow up (PYFU) in Ecuador to 3.6 per 100,000 PYFU in Uruguay. A low proportion of the C9orf72 repeat expansion was reported in Cuba and Brazil. We identified age at onset between 50 and 60 years. Survival time was higher than 40 months in half of the studies. Data from multiethnic populations reported a higher risk of developing ALS in Caucasians compared to admixed and Black populations. Conclusion: This review provides a perspective of ALS variability across Latin America and highlights specific differences when comparing to Europe and North America. However, we cannot draw firm conclusions because of different methodological concerns within the studies.