Background There are limited data on the nature, type and incidence of illness in football. Previous studies indicate that gastrointestinal and respiratory tract illnesses are most common.
Aim To describe the incidence and burden of illness in male professional football.
Methods Over the 4-year study period, 2011–2014, 73 professional football teams in Europe participated, with a total of 1 261 367 player-days recorded. All time-loss illnesses were recorded by the medical staff of each club. A recordable illness episode was any physical or psychological symptom (not related to injury) that resulted in the player being unable to participate fully in training or match play.
Results A total of 1914 illness episodes were recorded. The illness incidence was 1.5 per 1000 player-days, meaning that, on average, a player experienced an illness episode every second season, with a median of 3 days absence per illness episode. Severe illness (absence >4 weeks) constituted 2% of all illnesses. Respiratory tract illness was the most common (58%), followed by gastrointestinal illness (38%). Respiratory tract illness, gastrointestinal illness and cardiovascular illness caused the highest illness burden.
Conclusions The illness incidence among male professional football players is low compared with the injury incidence. We found that the highest illness burden was caused by illness to the respiratory tract, gastrointestinal tract and cardiovascular system.
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Several studies have evaluated the nature and incidence of injury in male professional football.1 ,2 There is, however, a lack of data on the nature and impact of illness in male professional football.
In a prospective study, Orhant et al3 followed a male football team for three consecutive seasons. They found that each player had, on average, 2.5 illness symptoms during a season, and approximately 20% of these resulted in absence from training or match play. Thus, following these results, half of the players will experience a time-loss illness period per season. In comparison, players at Champions League level will sustain on average two time-loss injuries per season.1 Recent studies from male international tournaments have shown an illness incidence from 7.7 to 16.5 per 1000 player-days, with approximately 40% leading to absence.4 ,5 Most players with a time-loss illness episode were able to return to play within 3 days.4 ,5 Symptoms from the upper respiratory tract and gastrointestinal tract are the most common causes of illness.3–5 Few studies have described the incidence and burden of illness in football, and we are not aware of any previous study investigating illnesses in several male professional teams over consecutive seasons.
The aim of this study was to describe the incidence and burden of illness in male professional football.
Materials and methods
All clubs in the male premier leagues (PLs) in Norway (Tippeligaen), Sweden (Allsvenskan) and England (English Premier League), and teams participating in the UEFA Champions League were invited to participate in the study. The Norwegian clubs were followed prospectively for four consecutive seasons, 2011–2014. The Swedish clubs were followed in 2011. The PL and UEFA clubs participated in three consecutive seasons, 2011/2012 to 2013/2014. A total of 73 different teams participated over the four-season study period for a varying number of seasons (1–4). In 2011, 28 Swedish and Norwegian clubs participated, 10 Norwegian clubs in 2012, 11 in 2013 and 9 in 2014. From the Champions League/PL cohorts, 31 teams participated in the 2011/2012 season, 33 in the 2012/2013 season and 38 in the 2013/2014 season. A total of 5070 player-seasons were reported, with 1 261 367 player-days recorded in total.
All players with a first-team contract were eligible for inclusion. Participation was voluntary and could be ended at any time. Players who had an ongoing illness when they were included in the study were allowed to participate, however, the existing illness episode was not recorded. Players who left the club on transfer before the end of a season were included for as long as they could participate.
The development of the UEFA Elite Club Injury Study (UEFA ECIS),6 and the data collection, have been described previously.7 From inception to the 2010 season, only injuries have been included in the surveillance, but starting from January 2011, illnesses were also recorded in the Norwegian and Swedish cohorts, and from July 2011 in the English Premier League and UEFA cohorts. Informed consent was collected from players at the start of each new season. A representative from each club medical team was responsible for reporting exposure and illness data to the study group. In the Norwegian and Swedish cohort, the illness registrations were, in most cases, conducted by the team physiotherapist, however, in the PL and UEFA cohorts, the team physician was responsible for recording illnesses. Exposure registration included individual player participation in football activity (minutes of exposure) on a standard exposure form. The attendance record was modified in December 2010 to also include illness as a reason for absence from training and match play, and a standard illness form was created. The illness form included questions regarding illness date, return date and type of illness.
A recordable illness episode was any physical or psychological symptom (not related to injury) that resulted in the player being unable to participate fully in training or match play. A player was regarded as ill until he was declared able to fully participate in all types of training and available for match selection by the medical team. Based on the type of illness stated on the illness form, illnesses were classified as respiratory tract illness (including asthma and allergy), gastrointestinal illness (stomach pain, diarrhoea and bowl problems), unexplained fatigue, neurological (including headache, migraine and nausea), psychological, cardiovascular, ophthalmological, dental or renal illness. Other illnesses were grouped and included dermatological, haematological and immunological illnesses. Illness severity was based on the number of days that elapsed from debut of illness absence to return to play and were categorised into: slight (0 days), minimal (1–3 days), mild (4–7 days), moderate (8–28 days) and severe (>28 days).
Results are presented as illness incidence (reported illness episodes/1000 player-days) with corresponding 95% CIs and illness burden (absence days per 1000 player-days). Layoff days, and number of missed trainings and matches were presented as median with corresponding IQR.
Of a total of 1914 illness episodes recorded during the study period, 1861 illness episodes were complete and therefore included for analyses (table 1). One club did not record the type of illness (n=46), while a further six forms were incomplete. The illness incidence was 1.5 per 1000 player-days (95% CI 1.5 to 1.6), meaning that, on average, a player sustained 0.4 illnesses per season.
Illness incidence and burden
Most recorded illnesses were of the respiratory tract, followed by gastrointestinal illnesses (table 1).
Most illnesses were of minimal (66%) or mild severity (25%), resulting in an absence of 1 week or less. Nine per cent of the illness episodes led to absence of >1 week (table 2). Cardiovascular and psychological illnesses had the highest proportion of severe illness episodes, including cardiac arrest, pulmonary embolism and depression. On average, each illness episode led to absence from 3.0 (IQR 2) training sessions and 0.6 (IQR 1) matches, with a median absence of 3 days (IQR 2). The greatest illness burden was caused by respiratory tract and gastrointestinal illnesses followed by cardiovascular illness (table 1).
Variation in illness
Figure 1 shows the variation in illness over the season. Illnesses were most frequent during the winter period regardless of a spring-to-autumn season, as seen in Sweden and Norway, or a Continental autumn-to-spring season.
This is the first study to record illnesses in male professional football over consecutive seasons in several clubs from different leagues. The main finding was that the illness burden in male professional football is low compared with injury burden, with each player experiencing a time-loss illness episode every second season compared with on average two time-loss injuries each season, thus making a time-loss incident due to injury four times as likely as that due to illness.1 The highest illness burden was caused by respiratory tract, gastrointestinal and cardiovascular illnesses, with 3.1, 1.1 and 0.8 absence days per 1000 player-days, respectively.
A few methodological issues are relevant to discuss when interpreting the study findings. Our injury and illness surveillance system was established prior to recent consensus statements.8 ,9 Hence, a limitation of this study is that the illness definition and classification is not in accordance with the consensus. The illness incidence reported in the current study is probably underestimated. Illness is comparable to overuse injuries, from a surveillance perspective—a significant proportion does not lead to time loss from sports participation.4 ,5 ,10 Players often continue to train and play with illness symptoms and reduced function, as they do with pain and other overuse-related symptoms. This results in under-reporting of the true illness incidence or prevalence in surveillance studies.11 Clarsen et al12 recently developed and validated a new questionnaire to monitor health problems, where the athletes registered problems that were suffered on a weekly basis. In a study of illness and injury patterns of Norwegian athletes preparing for the 2012 Olympic and Paralympic Games, illness placed a lesser burden on the athletes than overuse injuries, but it was still greater than that from acute injuries.13 Thus, despite the low illness incidence identified in this study, future epidemiological studies in team sports should adopt a similar approach and follow recent consensus statements8 when recording injuries and illnesses in male professional football. Another limitation is the lack of exact clinical diagnoses (epidemiological vs clinical study), compromising the ability of researchers to base recommendations on accurate clinical data. In some clubs in the Norwegian and Swedish cohort, the players are not always examined by a physician, instead, the illness or injury is either diagnosed by the physiotherapist or self-reported by the players, without further examination.
A strength of this study is that the method used is in accordance with the consensus statement for injury recording in football.14 Thus, we are able to compare the absence of time-loss illness episodes with time-loss injuries. In addition, this study includes a large number of illnesses over several seasons from many clubs in several PLs in top level football.
Incidence and burden of illness
Recent studies in male international rugby and football tournaments indicate an incidence of 7.7–20.7 per 1000 player-days, with a time-loss illness incidence of 3.0–16.2 per 1000 player-days.4 ,5 ,10 The illness incidence in our study on league football players (1.5/1000 player-days) was lower. There are other possible explanations for this in addition to the methodological constraints discussed above, including higher match frequency, jetlag, reduced restitution and increased contact between players during tournaments, possibly increasing the probability of spreading of infections. Schwellnus et al10 found that approximately 50% of players with illness episodes had symptoms at least 1 day prior to contact with the medical staff. Infection should be considered as a possible cause of illness. It is therefore important to implement preventative measures such as good personal hygiene, systematic sanitation, and recognition of symptoms and isolation of athletes with illness symptoms.10
The burden of illness is lower than the burden of injury in male football. Most illnesses are of minimal or mild severity, with 91% of the players being able to return to full participation within a week, which is consistent with the findings of earlier studies.4 ,5 ,10 The burden of respiratory tract and gastrointestinal illness is the largest, however, cardiovascular illness episodes are often severe and the third largest contributing factor to the illness burden.
Most illnesses affected the respiratory tract and the gastrointestinal tract, which is in accordance with other studies from football,3 ,4 ,5 athletics,15 ,16 rugby,10 aquatics17 ,18 and tennis,19 and during both, the summer and winter Olympics.20 ,21 Infection should be considered as a possible cause of illness, thus increased attention on illness preventive measures ought to be implemented in men's professional football. For instance, after the Turin Olympic Winter Games, the Norwegian Olympic team introduced several preventive measures to reduce the illness problem in the next Olympic Winter Games in Vancouver 2010.22 These preventive measures included screening for allergies and airway problems, vaccination, single rooms for athletes with airway problems, and widespread use of disinfectant hand gels and other sanitary measures.22 The Norwegian team experienced fewer illness episodes in Vancouver 2010 compared with Turin 2006, and compared with those experienced by other nations. Our study showed that illness linked to the respiratory system is the most common type of time-loss illness in male professional football.
Few studies have evaluated the incidence of psychological illness among male professional football players. The finding that only 11 psychological illness episodes in 5 players were recorded is probably an underestimation of the mental health problem in men's professional football. One reason might be that mental health problems are masked as fatigue, headache or other non-specific symptoms, either in the communication between the player and the medical staff or in the recording from the medical staff to the study group. Further studies are needed to more thoroughly explore mental health illnesses in football.
In conclusion, the illness incidence among male professional football players is low compared with injury incidence. We found that the highest illness burden was caused by illness to the respiratory tract, gastrointestinal tract and cardiovascular system.
What are the findings?
Illness is not a major contributor to absence from football training or match play compared with injury.
How might it impact on clinical practice in the future?
This study might contribute to increased attention being directed towards the implementation of preventive respiratory, gastrointestinal and cardiovascular illness measures in team sports.
The authors are grateful to the medical contact persons from all participating clubs. The Football Research Group was established in Linköping, Sweden, in collaboration with Linköping University and through grants from the UEFA, the Swedish Football Association, the Football Association Premier League Limited and the Swedish National Centre for Research in Sports. The Oslo Sports Trauma Research Center was established at the Norwegian School of Sport Sciences through generous grants from the Royal Norwegian Ministry of Culture and Church Affairs, the South-Eastern Norway Regional Health Authority, the IOC, the Norwegian Olympic Committee & Confederation of Sport, and Norsk Tipping AS.
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Contributors JB, OR, KK, JE, MW, MH and TEA contributed to study conception, design and development of the intervention. JB, HB and KK coordinated the study and managed all aspects, including data collection. JB conducted and initialised the data analyses, which were planned and checked by all the coauthors. JB and TEA wrote the first draft of the manuscript, which was revised in several steps by all the coauthors. All the authors had access to the data and approved the final manuscript. JB and TEA are the study guarantors.
Competing interests None declared.
Ethics approval The study design was approved by the UEFA Medical Committee and the UEFA Football Development Division, Nyon, Switzerland, for the UEFA Elite Club Injury Study; the FA Medical committee for the Premier League (England); the Institutional Ethical Review Board at Linköping University, Linköping, Sweden, for the Swedish professional league (#01-062); and the Institutional Ethical Review Board at Oslo University, Oslo, Norway, for the Norwegian professional league (#S-06188).
Provenance and peer review Not commissioned; externally peer reviewed.
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