The prevalence of asthma in Sweden is estimated to be 10% in the population aged 16–35 years [
The reason for the increased prevalence of asthma in winter endurance athletes is believed to be a consequence of repeated and prolonged inhalation of dry air, leading to heat loss, dehydration, and airway damage. In addition, the cooling process seems to induce bronchoconstriction via the parasympathetic nervous system, and subsequent rewarming leads to mucosal edema and further narrowing of the airways [
According to the guidelines, the first step in the treatment of asthma is a short-acting
A significant increase in use of asthma medication was documented among Finnish Olympic athletes between 2002 and 2009, even though there was no significant increase in the prevalence of either asthma or asthma symptoms, and 4% used ICS + LABA [
Selection of appropriate asthma medication is a key to disease control, and there is a lack of data on asthma control in elite endurance athletes. The primary aims of this study were to examine the level of asthma control and to determine the use of asthma medication in detail, specifically SABA/LABA, ICS, and ICS + LABA, among elite endurance athletes with current asthma. A secondary aim was to compare these findings with those in a reference population of patients with asthma recruited from health care registers.
This cross-sectional survey was part of a 5-year prospective postal questionnaire study on the prevalence, incidence, and remission of airway symptoms and asthma in Swedish elite endurance athletes. The study has been described in detail previously [
Two study populations were included. One study group included Swedish elite athletes participating in cross-country skiing, biathlons, ski-orienteering, or orienteering at international or highest national levels. These athletes consisted of students at seven National Elite Sports Schools, Swedish junior and senior national team members, students at the three Swedish Ski Universities where elite athletes combine an elite career with higher education, and the top 80 Swedish orienteers aged 20–30 years according to the national ranking in 2011. A total of 711 eligible athletes were invited to participate in a postal questionnaire survey in September 2014 and 2015. The other study (reference) group included patients who were identified through primary and specialist health care records to have been born between 1985 and 1999 in the region of Jämtland-Härjedalen and to have a diagnosis of asthma (ICD code J45) in 2011–2015. Patients with asthma who were already included in the group of athletes were excluded. In total, 1026 eligible reference subjects were invited to participate in the postal questionnaire survey in September 2016. To match the smoking habits of the athletes, ex-smokers and current smokers were excluded from the analyses.
The postal questionnaire was a shortened version of the European Community Respiratory Health Survey II, which includes questions on asthma, drug utilization, airway symptoms, smoking history, family history of asthma, and health care contacts [
The key variables investigated in the study are outlined below, along with an explanation of how each variable was assessed: “Physician-diagnosed asthma” was identified by the responses to the questions “Have you ever had asthma?” and “Was it diagnosed by a doctor?” “Medication” was identified by the responses to the question, “Have you used any asthma medication, including inhalers, sprays, or pills, during the last 12 months?” Asthma medication was categorized as SABA/LABA, ICS, or ICS + LABA. Montelukast was used by a small proportion in both study groups and is not presented in the results. The frequency of use of asthma medication was categorized as “never,” “sometimes,” “for more/less than 2 months per year,” or “daily.” “Current asthma” was defined as physician-diagnosed asthma and use of asthma medication during the previous 12 months. “Age of asthma onset” was determined by the response to the question, “How old were you when you had your first asthma attack?” “Smoking status” was determined by the responses to the questions, “Have you been smoking one or more cigarettes per day for at least one year?” and “Have you been smoking during the last month?” “Training” was assessed by the response to the question, “On average, during the last 12 months, for how many hours/week did you exercise so much that you got out of breath or became sweaty?” “Family history of asthma” was determined by the response to the question, “Do any of your parents or siblings have asthma?” “Allergy” was identified from the response to the question, “Do you have any nasal allergies, including hay fever?” “Health care contact” was assessed by the response to the question, “Have you had any health care contacts due to airway problems in the last 12 months?” “Asthma control” was assessed using the ACT and was reported both as a continuous variable ranging from 5 to 25 points and was categorized as “uncontrolled” (≤19 points), “partially controlled” (20–21 points), or “well controlled” (≥22 points) [
The assumption was made a priori that 25% of the athletes and 15% of the reference subjects would be using ICS + LABA daily. We calculated that inclusion of 146 athletes would require 294 reference subjects to reach a power of 80% with an
Reference subjects who answered “No”
Continuous variables were compared between the study groups using Student’s
After the bivariate analysis, multivariate Poisson regression analyses were performed in each group, and the data for the two study groups were then pooled to test for an independent association between the ACT score and being an elite athlete. Subject’s age, age at asthma onset, allergy, shortness of breath after exercise, and respiratory-related health care contacts during the previous 12 months were included as covariates in the model.
Four hundred and sixty-nine (66%) of the 711 athletes invited to participate in the survey responded, and all were nonsmokers. Of these, 141 (20%) reported having physician-diagnosed asthma. Three hundred and ninety-seven (39%) of the 1026 eligible reference subjects responded. Of these, 122 were excluded either because they did not have physician-diagnosed asthma
Flowchart of study participants.
A detailed description of the two study populations is presented in Table
Demographic and clinical characteristics of a group of Swedish elite endurance athletes and a health care-based reference population of patients with asthma.
Athletes |
References |
| |
---|---|---|---|
Age (years), mean (SD) | 21.5 (4.5) | 25.6 (6.4) |
|
Women | 79 (56) | 181 (66) | 0.051 |
Training (hours/week), mean (SD) | 11.7 (4.4) | 4.9 (4.5) |
|
Current asthma | 108 (77) | 243 (88) |
|
Age of asthma onset (years), mean (SD) | 13.3 (4.5) | 9.8 (6.7) |
|
Allergy | 54 (50) | 203 (74) |
|
Family history of asthma | 78 (59) | 149 (58) | 0.866 |
Health care contacts1 | 25 (18) | 75 (27) |
|
Shortness of breath2 | 27 (19) | 95 (35) |
|
The data are presented as
When classified by ACT scores, 58% of the athletes with current asthma reported that their asthma was well controlled, whereas 23% reported partially controlled asthma and 19% reported uncontrolled asthma (Table
Level and distribution of asthma control in Swedish endurance athletes with current asthma.
Uncontrolled |
Partially controlled |
Well controlled |
|
|
---|---|---|---|---|
Female sex | 11 (58) | 17 (71) | 32 (54) | 0.378 |
Age (years), mean (SD) | 19.8 (3.7) | 21.3 (4.2) | 22.2 (4.8) | 0.174 |
Age of asthma onset (years), mean (SD) | 13.4 (4.3) | 16.5 (4.0) | 12.1 (4.8) |
|
Allergy | 9 (47) | 14 (58) | 23 (44) | 0.517 |
Training (hours/week), mean (SD) | 12.9 (2.7) | 13.1 (3.8) | 11.1 (4.8) | 0.855 |
Shortness of breath1 | 8 (42) | 7 (29) | 10 (17) | 0.079 |
Health care contacts2 | 9 (47) | 8 (33) | 7 (12) |
|
Family history of asthma | 12 (63) | 13 (62) | 37 (69) | 0.828 |
Daily SABA/LABA | 14 (74) | 12 (50) | 15 (25) |
|
Daily ICS | 9 (47) | 7 (29) | 18 (31) | 0.353 |
Daily ICS + LABA | 10 (53) | 8 (33) | 13 (22) |
|
The data are presented as
Level and distribution of asthma control in a health care-based reference group of patients with current asthma who have never smoked.
Uncontrolled |
Partially controlled |
Well controlled |
|
|
---|---|---|---|---|
Females | 55 (67) | 35 (61) | 67 (66) | 0.779 |
Age (years), mean (SD) | 24.1 (4.2) | 25.6 (4.7) | 26.7 (7.8) |
|
Age of asthma onset (years), mean (SD) | 7.9 (6.2) | 9.7 (7.6) | 11.3 (6.3) |
|
Allergy | 69 (84) | 42 (74) | 74 (73) | 0.148 |
Training (hours/week), mean (SD) | 5.0 (5.5) | 5.3 (4.4) | 4.7 (3.7) | 0.827 |
Shortness of breath1 | 48 (59) | 21 (38) | 24 (24) |
|
Health care contacts2 | 39 (48) | 15 (26) | 20 (20) |
|
Family history of asthma | 46 (61) | 32 (62) | 54 (56) | 0.739 |
Daily SABA/LABA | 50 (61) | 14 (25) | 8 (8) |
|
Daily ICS | 26 (32) | 13 (23) | 17 (17) |
|
Daily ICS + LABA | 36 (44) | 13 (23) | 38 (37) |
|
The data are presented as
In the reference group, 102 patients (42%) reported well-controlled asthma (Table
Athletes whose ACT scores indicated well-controlled asthma reported no or little limitation in daily activities (Figure
Results for each ACT question. The results are stratified by study population and ACT category. (a) “In the past 4 weeks, how much of the time did your asthma keep you from getting as much done at work, school or at home?” (all of the time, most of the time, some of the time, a little of the time, or none of the time). (b) “During the past 4 weeks, how often have you had shortness of breath?” (more than once a day, once a day, 3 to 6 times a week, once or twice a week, or not at all). (c) “During the past 4 weeks, how often did your asthma symptoms (wheezing, coughing, shortness of breath, chest tightness, or pain) wake you up at night, or earlier than usual in the morning?” (4 or more nights a week, 2 to 3 nights a week, once a week, once or twice, or not at all). (d) “During the past 4 weeks, how often have you used your rescue inhaler or nebulizer medication?” (3 or more times per day, 1 or 2 times per day, 2 or 3 times per week, once a week or less, or not at all). (e) “How would you rate your asthma control during the past weeks?” (not controlled at all, poorly controlled, somewhat controlled, well controlled, or completely controlled).
The athletes had a significantly higher mean ACT score than the reference subjects (Table
Bivariate analyses comparing ACT scores and levels of the control based on ACT scores between Swedish elite endurance athletes and a reference group of patients with current asthma who have never smoked.
Athletes |
References |
| |
---|---|---|---|
ACT score, mean (SD) | 22.2 (2.9) | 21.0 (4.0) |
|
Uncontrolled1 | 19 (19) | 81 (34) |
|
Partially controlled2 | 24 (24) | 57 (23) | 0.965 |
Well controlled3 | 59 (58) | 102 (42) |
|
The data are presented as
Of the athletes with current asthma, 39% used SABA/LABA daily, 31% used ICS daily, and 31% used ICS + LABA daily. Overall, 43% of the athletes used ICS or ICS + LABA daily. Athletes with an ACT score indicating uncontrolled asthma reported more daily use of
Use of asthma medication by Swedish elite endurance athletes and a reference group of patients with current asthma and a statistical comparison between the two groups.
Athletes |
References |
|
|
---|---|---|---|
SABA/LABA | |||
Never | 32 (30) | 40 (17) | |
Sometimes | 30 (28) | 101 (42) | |
Less than 2 months | 0 (0) | 12 (5) | |
More than 2 months | 4 (4) | 16 (7) | |
Daily | 42 (39) | 73 (30) | 0.101 |
ICS | |||
Never | 56 (52) | 135 (56) | |
Sometimes | 14 (13) | 34 (14) | |
Less than 2 months | 1 (1) | 8 (3) | |
More than 2 months | 3 (3) | 9 (4) | |
Daily | 34 (31) | 56 (23) | 0.099 |
ICS + LABA | |||
Never | 64 (59) | 126 (52) | |
Sometimes | 5 (5) | 17 (7) | |
Less than 2 months | 3 (3) | 5 (2) | |
More than 2 months | 3 (3) | 7 (3) | |
Daily | 33 (31) | 87 (36) | 0.326 |
To compare the two groups with regard to use of asthma medication, the subjects were dichotomized into those who did and did not use SABA/LABA, ICS, or ICS + LABA daily;
This postal questionnaire survey evaluated disease control and use of asthma medication in 141 elite endurance athletes with asthma and a reference population of 275 nonathletic patients with asthma. Among the elite athletes, 108 (77%) had current asthma, that is, had used asthma medication during the previous 12 months; 39% used SABA/LABA, 31% used ICS, and 31% used ICS + LABA on a regular daily basis. According to the ACT scores, 19% of athletes had current asthma that was uncontrolled, 25% had partly controlled asthma, and 58% had well-controlled asthma. Athletes with uncontrolled asthma reported frequent use of SABA/LABA; after adjustment for confounding factors, their ACT scores and daily use of asthma medication did not differ significantly from the values observed in the reference population of patients with asthma who had never smoked.
To the best of our knowledge, this is the first study to compare asthma control and use of asthma medication between elite athletes with asthma and nonathletic patients with asthma. In order to perform at their best, athletes should not be limited by respiratory problems. This is especially true for those with high ventilation rates, such as endurance athletes. Hence, it was not unexpected that the majority (almost 60%) of the endurance athletes in the present study had well-controlled asthma. However, we were surprised to find that up to one-quarter of the elite endurance athletes were classified as having partly controlled asthma and nearly one-fifth as having uncontrolled asthma, which suggests that it is possible to pursue endurance sports at an elite level without well-controlled asthma. Another explanation could be that ACT is an inadequate tool for assessment of asthma control in elite athletes. Depending on how the athletes interpret the questionnaire, both over- and underestimation of asthma control may occur. Although well validated, ACT may have poor accuracy for assessment of uncontrolled asthma [
Several studies have assessed asthma control using ACT in “nonelite athletic” subjects. In those studies, the prevalence of uncontrolled asthma (defined as an ACT score ≤ 19 points) varied in the range of 50%–58% [
Fifty-two (48%) of the 108 athletes with current asthma in our study used a fixed combination of ICS + LABA sometimes to daily, which is similar to observations in Finnish Olympic athletes reported in 2004 [
The relatively high use of ICS or ICS + LABA in the present study may also explain why the athletes used less SABA/LABA when compared with Australian summer sports athletes [
Athletes who used SABA/LABA frequently tended to have uncontrolled asthma when classified by their ACT scores. However, frequent use of SABA/LABA contributes to a lower ACT score, which may cause asthma to be classified as partially controlled or uncontrolled. We suggest that this particular group of athletes should receive extra medical attention in order to evaluate and optimize their disease control. However, this study was cross-sectional, so we cannot conclude that frequent use of SABA/LABA is a cause or an effect of uncontrolled asthma. It is in line with our clinical experience that a large proportion of elite endurance athletes are/feel controlled on Step 1 treatment with SABA only and seldom need/use controllers (ICS or ICS/LABA).
In our reference group of patients with asthma who had never smoked, 31% used ICS + LABA daily, which is higher than the rate of 19% reported in a population-based cohort of patients with asthma [
The present study has some limitations in that the diagnosis of asthma, level of asthma control, and use of asthma medication were based on self-reported data and were not confirmed by medical records or prescriptions of medication. The low response rate of 39% in the reference group may represent a degree of selection bias. A nonresponse analysis would be of value, however, was not included in the original study design and ethical approval. Two Scandinavian questionnaire-based studies found that nonresponders were significantly more likely to be men, younger, and current smokers but found no significant differences with regard to the prevalence of asthma-like symptoms or use of asthma medication [
The 66% response rate for the athletes in this study can be considered representative of Swedish endurance athletes, who are competing mostly in a cold climate. Given that the Swedish guideline for asthma treatment follows the international guidelines, the results of our study may be generalizable to endurance athletes outside of Sweden.
It has been shown that German elite athletes with high ventilation rates use significantly more asthma medication than those with medium or low ventilation rates, but no significant difference in use was observed between summer and winter athletes [
According to our postal questionnaire survey, 39% of Swedish endurance athletes with current asthma used SABA/LABA and 31% used ICS + LABA daily. Most of the athletes had well-controlled asthma (58%), and those with uncontrolled asthma (19%) reported frequent use of SABA/LABA. Their ACT scores and daily use of asthma medication did not significantly differ from the results in the reference population of patients with asthma who had never smoked. Being an elite endurance athlete per se was not associated with either the ACT score or daily use of asthma medication. All patients with asthma should be monitored regularly. Elite endurance athletes using
The authors declare that there are no conflicts of interest regarding the publication of this article.
The authors wish to thank the coaches at the Swedish National Elite Sport Schools, national teams, and ski universities for recruitment and data collection, and the Swedish Ski Association, Biathlon Association, and Swedish Orienteering Federation for recruitment and general support. This study was financially supported by the Visare Norr Fund, Northern County Council’s Regional Federation, and by the Research & Development Unit of the Jämtland County Council, Sweden.