Epidemiology and Clinical History of ALS

Halfway through the twentieth century the first epidemiological studies of a disease characterised by a combination of dementia, Parkinson´s and ALS found in the native population of Guam (where the incidence of ALS was 50 to 150 times more than that in the rest of the world) were published. The latter fact aroused great interest among researchers since it allowed ALS to be looked at from a different perspective 5. ALS, along with Alzheimers and Parkinsons, is one of the more significant neurodegenerative diseases.

The average onset age for ALS is between 60-69 years of age, with a peak incidence between 70-75 years of age and a lowering of the rate of incidence after that, as opposed to what occurs with Parkinsons or Alzheimers 6. It is worth mentioning that cases of hereditary origin occur at earlier ages, some 10 years before in many instances 7. In general, incidence amongst men is slightly higher than amongst women, but in studies of Afro-Americans this difference is inverted.

In the case of Spain, it is probable that the average onset age is below that observed internationally, since it essentially appears between the ages of 40 and 70 8. According to a recent survey, the average onset age for non-specific symptoms was 48.8 years, while that for clear weakness or atrophy was 50.2 years 9.  Therefore the majority of people diagnosed in Spain are of working age, fully productive and have all of their lives ahead of them.

The number of those affected by ALS is low in comparison with other illnesses, which means that it is an invisible and minority condition. In general, the epidemiological studies carried out make it clear that there is an incidence of between 1 to 2 cases per 100,000 inhabitants per year, these number being exceeded in areas of high incidence (the island of Guam, the Kii peninsula, the population of Irian Jayan, the Anguru tribe in Australia and the population of Guadeloupe in the Caribbean) 6, suggesting that each year some 120,000 new cases worldwide are diagnosed 10. From this data it is estimated that ALS will affect one person in every 400-800, should they live long enough 6.  In spite of the current incidence not being extremely high, in the last decades an increase in the number of cases diagnosed has been observed, probably due to improvements in diagnosis and greater longevity of the population in general.

In Spain, the incidence is similar to that of other developed countries since 1.4 cases per 100,000 inhabitants are detected annually 6.  It is estimated that in Spain 3 new cases are diagnosed every day, meaning 900 new cases each year. In this sense, it is worth noting that ALS is an unpredictable disease which can appear in anyone, and it is calculated that some 40,000 Spaniards alive today will develop the disease during their lives 8.

The prevalence of this disease is low due to the high mortality rate associated with it; published studies show that in general there are 2 – 5 cases per 100,000 inhabitants6, and it is estimated that in the world there are only half a million people with the condition11–13. Nonetheless, in spite of the low number of cases, ALS is considered to be the most common motor neurone disease amongst adults, as well as being the most serious. The pathology is more frequent in men than in women. The average onset age varies between 55 and 65 years approximately; however, hereditary cases manifest themselves at earlier ages, some 10 year earlier in many instances. In the majority of cases the condition starts with spinal symptoms, and less frequently (around 1/3 of cases), with bulbar symptoms. 

In Spain few epidemiological studies have been carried out, but in the most recent one, slightly higher levels than those found in the world in general have been observed, with an incidence of 5.4 cases per 100,000 inhabitants6, probably due to the higher life expectancy of our country. From this data, it is estimated that there are some 4,000 people affected in Spain at this point in time8.

Therefore, since the incidence is low, ALS is considered to be a minority disease. This has very negative repercussions on those affected since the authorities do not deem this disease to be a priority, and patients are frequently forgotten about, lacking sufficient resources either for research or to cover the many care and support requirements that they have. 

In ALS a progressive degeneration of the motor neurone system can be observed, affecting the skeletal musculature as a result. The clinical characteristics typical of ALS are those resulting in a loss of function in the upper and lower motor neurons to different degrees, depending on the stage of the disease15. ALS can be characterised as a passage through symptoms affecting the primary and secondary motor neurons. In cases of bulbar onset the average survival rate tends to be 2-3 years, whilst in cases of spinal onset it is approximately 3-5 years14.

The overall mortality rate for Spain is calculated to be 1.49 per 100,000, being somewhat higher in men, with a peak between the ages of 60-69 years. According to the INE (Instituto Nacional de Estadistica (Spanish National Statistics Institute), 965 patients in Spain died of ALS in 2011, practically the same number as the new cases diagnosed in the same year. The number of deaths has been progressively increasing since 2000, when there were 682, probably down to better classification and knowledge of the disease6,16.

These figures make the enormous impact the disease has in terms of mortality very clear, since the average survival rate does not rise above 2-5 years17. The number of cases in Spain is so high that it is identical to that of the number of new cases diagnosed annually. This fact causes the incidence of ALS to be kept very low compared to other diseases which although having the same frequency, have a much higher survival rate.

Amongst the signs of impairment of the primary or upper motor neuron we may observe: loss of dexterity, loss of muscle strength (weakness), increase in spasticity, excess muscle stretching or pathological hyperreflexia, pathological reflexes, excess reflexes in atrophic extremities, pseudobulbar paralysis (spastic) and emotional lability1. Speech is also slow and forced, there is emotional lability and chin reflexes are pronounced15.

On the other hand, if we focus on the signs of impairment of the secondary or lower motor neuron we can highlight: loss of muscle strength (weakness), muscular atrophy, hyperreflexia, muscular hypotonia or weakness, twitching, muscular cramps and bulbar syndrome1. Speech is distorted, the tongue being weak and atrophied15

The advance of this disease, in the majority of cases, is rapid and unpredictable, leading to respiratory failure and resulting in death. The bulbar functions are severely affected (the ability to speak and swallow) 18. Patients also present symptoms such as twitching, loss of muscle mass and weakness19.


The initial stages of ALS do not present a unique and defined clinical pattern, rather they are characterised by a great clinical variation. Individuals with ALS do not experience the same symptoms or the same sequences of modes of progression, and the illness can start interchangeably in the speech muscles, in those required to swallow, or even in the hands, arms, legs or feet. Many of these symptoms are easily put down to other diseases, which enormously complicates the diagnosis since professionals can easily confuse them with other pathologies. This fact, together with the absence of biological markers, to a great extent makes early, certain diagnosis difficult 20. For this reason, diagnostic criteria based on the presence of certain clinical signs have been established, making something like a differential diagnosis possible.

In 1990, the World Neurological Federation, at a meeting in El Escorial (Madrid), created a series of criteria for the diagnosis of this disease, known as the ¨El Escorial Criteria¨. These criteria, which were re-evaluated in 2000 21, have enabled greater uniformity in diagnosis, fundamental in terms of epidemiological and physiopathological studies and in tests of new therapies.

Hardly anybody affected by ALS is seen directly, at the first consultation, by a neurologist. However, in many cases, general practitioners do not have sufficient information about the symptoms and alarm bells to be able to detect the disease17.

This lack of information often leads to an incorrect diagnosis which in turn leads to wrong referrals to other specialisms such as ear, nose and throat or traumatology, resulting in long delays to the final diagnosis which has to be carried out by a neurologist. In the same way, these errors can cause unnecessary and even counterproductive treatments for ALS patients 7.


In spite of the intense research efforts into the subject, the causes of ALS remain fairly unclear. Currently there are no effective treatments for it, the priority being placed on obtaining preclinical data to underpin therapy which will alleviate the progress of the disease. However, many studies have been undertaken with a view to improving the quality of life and survival potential of patients.

ALS patients present a series of characteristic signs and symptoms which have to be identified and treated in specific ways, amongst others these are: sialorrhoea (salivary hypersecretion), cramps, spasticity, emotional lability, depression, sleep disturbance, constipation and vein thrombosis. Symptomatic treatment of patients, as far as is possible, allows their quality of life to be improved.

Currently there is no curative treatment for the illness, but the quality of life of patients as well as their survival time can be changed significantly with the application of appropriate medical attention. However, the care required by ALS patients is complex, and the healthcare system is not geared up for this complexity.

In the last few years research has advanced sufficiently to be able to demonstrate that nutritional and pneumonological treatment of patients is capable of not only improving the quality of life of patients but also their life expectancy. The use of non-invasive mechanical ventilation reduces patients´ breathing difficulties as well as improving their rest22.

In this way, within a multidisciplinary treatment coordinated by the neurologist and supported first of all by pneumonology and then by other disciplines such as rehabilitation (of the limbs as well as the respiratory system), digestive and nutrition specialists, psychologists, ear nose and throat and palliative experts, it can be shown that patients treated in these types of multidisciplinary and coordinated centres not only see their quality of life improved but also an extension of their life expectancy; all of this presupposes the best internationally confirmed treatment that currently exists for ALS patients22.

In spite of not having problems accessing clinical treatment, patients suffer the consequences of a fragmented healthcare system which is incapable of providing their needs in a coordinated manner. Today, patients with ALS do not receive coordinated care from all of the professionals associated with their wellbeing, be it in the healthcare or the social sector23.

The integrated attention needed by patients requires the organisation of multidisciplinary units relying on the involvement of different specialists. However, in our country, this is the exception rather than the rule, so that not all ALS patients receive the same quality of care 9,24.


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