Amyotrophic Lateral Sclerosis Descriptive Epidemiology: The Origin of Geographic Difference

Abstract

Amyotrophic lateral sclerosis (ALS) epidemiology has rapidly developed in the last 30 years alongside the evolving changes in concepts in the field of clinical ALS and also due to the recent proposals of new classification system for motor neuron diseases. Many of these changes in the clinical scenario have been determined through the results of ALS population-based studies conducted in the last 20 years primarily in Europe. All the evidences converge to show that ALS risk is different across continents and ethnicities. In a European registry consortium named EURALS, ALS incident cases were drawn from a source population comprising almost 24 million people across Europe (ALS cases: 1028) and the estimated incidence was 2.2 per 100,000 person-years (py) for the general population. In contrast, other population-based studies have measured the lowest incidence in East Asia to be 0.89 per 100,000 py and in South Asia to be 0.79 per 100,000 py. A large part of Africa, Latin America and Asia does not have any population-based studies. The origin of geographic difference in ALS incidence is a matter of debate. Probably, this is partly due to genes (C9ORF72) and partly due to environmental risk factors. The rapid disappearance of ALS Foci in Guam, Kii, and West Guinea underline the importance of changes in lifestyle and environmental factors. The Global Burden of Disease, a project aiming to describe the burden of all diseases and injuries across all the countries of the world with a standardized protocol, has collected heterogeneous sources of data to estimate the burden of motor neuron diseases. The demographic changes related to increased expectation of life and the growth of the world population indicate that the load of motor neuron disease is rapidly moving toward 400 thousand prevalent cases. The burden is expected to shift toward Asia and Africa in the next decades for the rapid increase of expectation of life of countries with high demographic impact.

ALS is a multistep process in South Korean, Japanese, and Australian patients

“…Geographic differences in ALS incidence have been documented, with incidence being highest in the European (Caucasian) and lowest in southeast Asian patients. 13 The origin of these geographic differences remains a matter of debate, being ascribed to variations in genetic and environmental factors as well as life expectancy. 13 Furthermore, it could be argued that a greater number of steps are required to develop ALS in the Asian population, thereby leading to lower incidence rates.…”

“…13 The origin of these geographic differences remains a matter of debate, being ascribed to variations in genetic and environmental factors as well as life expectancy. 13 Furthermore, it could be argued that a greater number of steps are required to develop ALS in the Asian population, thereby leading to lower incidence rates. Establishing a multistep model in the South Korean and Japanese ALS population, particularly the number of required steps, could be of pathophysiologic importance.…”

Role of plants, environmental toxins and physical neurotoxicological factors in Amyotrophic lateral sclerosis, Alzheimer Disease and other Neurodegenerative Diseases

“…Two had family history of ALS, and one, of parkinsonism-dementia. These indings con irm that Kii type ALS occurs continuously in and near the Hohara focus'' [41].…”

“…The demographic changes related to increased expectation of life and the growth of the world population indicate that the load of motor neuron disease is rapidly moving toward 400 thousand prevalent cases. The burden is expected to shift toward Asia and Africa in the next decades for the rapid increase of expectation of life of countries with high demographic impact" [41].…”

The NGS technology for the identification of genes associated with the ALS. A systematic review

“…The c9orf72 repeat expansion accounts for a significant percentage of familial and sporadic ALS in Caucasian populations but is rare in Asian cohorts. The origin of this mutation dates back 1500 years to the Vikings contributing to its spread through their European invasion 56,57 . At present, we known that the most common genetic mutation in Caucasian population is c9orf72, accounting more than 40% of FALS and 5%‐20% of SALS, with particular high prevalence in Finland 57 .…”