Research to date has revealed that up to 25% of people with a REM sleep disorder had, at some point in their youth, a head trauma. A new study, carried out by researchers at Clínic-IDIBAPS and which has just been published in the Journal of Neurology, has now shown that playing football professionally is also a factor that predisposes to these disorders and possibly associates it with the greater possibility that these people have of suffering a concussion.

To carry out this study, the researchers analyzed the characteristics of 338 patients diagnosed with a REM sleep disorder and treated between March 1994 and March 2022 at the Sleep Disorders Center of the Neurology Service of the Clínic. Of these, 228 were men, of whom 6 had been professional footballers with an average career of 13 years, representing 2.6% of patients. "The vast majority of patients were not professional footballers, but we do see that there is a predisposition when we compare these data with a control group or with the general population," explains Àlex Iranzo, neurologist at Hospital Clínic Barcelona and head of the Clinical Neurophysiology group at IDIBAPS.

The way to demonstrate this predisposition was to compare this group of patients with REM sleep disorders with another group of patients with other sleep disorders, also of 228 patients. In this case it was seen that there were no players in the control group. Likewise, the data of all federated footballers between the 60s and 70s were searched and it could be seen that these represented 0.6% of the entire Spanish population.

"These data are important, but now it would also be essential if they could be replicated through other studies in other centers," adds Iranzo, who pointed out that although this association between professional football and REM sleep disorders has been seen, it is not known exactly what is the cause of this. "Traumatic brain injury may be the most plausible hypothesis, but there could also be other causes, such as the use of certain insecticides on the playing fields, the diet followed by these people or other causes."

Relationship with neurodegenerative diseases

Previous studies led by Iranzo had already shown that REM sleep behavior disorder is the first manifestation of neurodegenerative diseases, such as Parkinson's disease or dementia with Lewy bodies, all characterized by the accumulation of deposits of the alpha-synuclein protein. "We have seen that five years after the diagnosis of REM sleep disorder, 25% of patients develop one of these neurodegenerative diseases. At ten years, the percentage rises to 75%. And by age 15, it's already 90%," says the neurologist.

The study that is now presented is the first of its kind in Spain, but not the first to analyze professional footballers and their relationship with neurodegenerative diseases. There are two previous studies, one carried out in Scotland and the other in Sweden that have also investigated this relationship, although from a different perspective.

"The design of these studies has been very different. In Scotland and Sweden they went to investigate how many players there were federated and then checked in their files what were the causes of their death and what illnesses they had had. Ours is different because we have treated people who came with a problem and we have investigated what their profession had been, "says Iranzo, noting that in any case they are two sides of the same coin.

The results obtained in these studies are in line, however, with research carried out in other contact sports, such as American football, boxing or martial arts, where head injuries also frequently occur. "It has been seen that in general all these contact sports pose a risk of between 3 and 4% of greater proportion of propensity to neurodegenerative diseases," says Iranzo.

Consequences of the study

All these data are very possible that they could have consequences in the near future, as pointed out Gil Rodas, consultant doctor of Sports Medicine of the Clínic. "It is true that we have greatly minimized these injuries over the years and important institutions, such as FIFA, have realized the consequences that these traumas can have in the long term."

Thus, Gil Rodas points out the establishment of action protocols when a traumatic brain injury occurs during the game or in training and that any player who suffers from them should not participate again until at least six days after the incident to evaluate that there have indeed been no serious sequelae of the impact. "However, we still need to study more preventive strategies that help limit the number of head strokes in training and matches. What is clear is that the studies we have explain that having these blows repetitively can have long-term consequences and is something we must consider."

Despite these results, we also wanted to convey a message of calm and tranquility. "It should be borne in mind that most patients with REM stage sleep disorders were not professional footballers and that most professional footballers do not develop neurodegenerative diseases. There are many other causes involved, but it is true that playing football professionally is another risk factor," concludes Iranzo.

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