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08-11-2018 | Neurology | Main feed | News

Global burden of motor neuron diseases quantified

medwireNews: High-income countries currently have the highest rates of motor neuron diseases worldwide, and the burden is increasing with the ageing population, shows an analysis of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016.

“Despite the absence of a cure for motor neuron diseases, these findings are important to health service planning as the care of patients with motor neuron disease is intensive and expensive”, Giancarlo Logroscino (University of Bari Aldo Moro, Italy) and the GBD 2016 Motor Neuron Disease Collaborators remark in The Lancet Neurology.

The GBD includes data from 195 countries and territories that were collected between 1990 and 2016 and the current analysis focused on amyotrophic lateral sclerosis, spinal muscular atrophy, hereditary spastic paraplegia, primary lateral sclerosis, progressive muscular atrophy and pseudobulbar palsy.

In 2016, there were 330,918 individuals worldwide who had a motor neuron disease. In the same year, motor neuron diseases caused 926,090 disability-adjusted life–years (DALYs) and 34,325 deaths.

The worldwide all-age prevalence was 4.5 per 100,000 people, and the researchers found that between 1990 and 2016, all-age prevalence increased more than the age-standardised prevalence (18.8 vs 4.5%), “indicating that the largest part of the global prevalence increase was due to ageing”, they write.

The all-age incidence rate was 0.78 per 100,000 person–years, while the all-age cause specific mortality rate was 0.46 per 100,000 person–years.

Approximately half of the prevalent cases worldwide occurred in countries with the highest sociodemographic indices (SDI). Specifically, the highest age-standardised prevalence was in high-income North America (16.8 per 100,000 people) followed by Australasia (14.7 per 100,000 people) and western Europe (12.9 per 100,000 people).

By contrast, the lowest age-standardised prevalence was in central sub-Saharan Africa (1.2 per 100,000 people).

Logroscino et al suggest that some of the geographic differences could be due to more accurate diagnosis in the high SDI countries compared with the low and middle SDI countries, but they also point out that high SDI countries in the Asia Pacific region had a “lower than expected” prevalence and incidence.

“This geographical heterogeneity suggests that the differences in the prevalence and incidence of motor neuron disease might be due to ethnicities and ancestries, and that the apparent relationship with SDI might be spurious”, the researchers remark

Furthermore, the team found that none of the 84 risk factors quantified in GBD showed an association with motor neuron disease incidence “suggesting other unmeasured risk factors might have a role.”

In an accompanying comment, Orla Hardiman from Trinity College Dublin, Ireland describes the analysis as “an important first step in defining the societal impact” of motor neuron diseases.

“The study provides a useful framework within which the global impact of these diseases can be examined, and shows the substantial gaps in our knowledge, particularly relating to understudied populations of non-European or mixed ancestry”, she concludes.

By Laura Cowen

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