Asthma is an inflammatory airway disease with episodes of narrowing airways leading to wheezing and shortness of breath [
Adult cross-country skiers are especially prone to having asthma and exercise-induced asthma, and this is assumed to be caused by repeated and intense breathing of dry and cold air [
The present study aimed to determine the prevalence of asthma and respiratory symptoms among competitive cross-country skiers in early adolescence in comparison to a reference group. Our hypothesis is that children in early adolescence who compete in cross-country skiing have a higher prevalence of asthma and respiratory symptoms than a population-based reference group of similar ages.
The study was approved by the Ethical Review Board in Umeå, Sweden.
This study is a postal questionnaire survey addressing adolescent skiers from all regions participating in the Swedish National Cross-country Championship together with a random population-based reference population of adolescents with similar ages. Study subjects received a postal questionnaire based on the European Community Respiratory Health Survey II (ECHRSII) [
All skiers between the ages of 12–15 years from all geographic regions of Sweden (
The reference group consisted of a random population-based sample of adolescents aged 13-14 years (
The group of skiers received the questionnaire through the team coaches at the Swedish National Championship in February 2016, and the reference group received the postal questionnaire in January and February 2015. Signed consent had to be given by both the guardian and adolescent. One reminder was sent to nonresponders.
The key study variables were as follows: (1) self-reported asthma (physician-diagnosed asthma and use of asthma medication the last 12 months), (2) current wheezing, (3) wheezing without a common cold, (4) exercise-induced wheezing (during the previous 12 months), (5) smoking in family (mother, father, or other person in the family who smokes), (6) use of short-acting/long-acting B2-agonists (SABA/LABA), inhaled corticosteroids (ICS), ICS + LABA, or other medication (“have you used short-acting/long-acting B2-agonists (SABA/LABA), inhaled corticosteroids (ICS), ICS + LABA or other medications (e.g., leukotriene receptor antagonist and cromoglicate) in the last 12 months?”), (7) the presence of allergic rhinitis (report of hay fever or other allergies with rhinitis or conjunctivitis), and (8) exercise (“on average, how many hours per week have you exercised so much that you were out of breath or sweated in the last 12 months?”). The ACT score was a continuous variable ranging from 5 to 25 points, and the cutoff value for controlled asthma was >19 points [
The prevalence of asthma in the reference group was assumed to be 8%, and we cautiously expected a response rate of 40%. To be able to show a difference in prevalence between the groups of 7% (alpha 0.05 and beta 0.20), 183 cross-country skiers were needed. Medians and interquartile ranges (IQR) were used for skewed data. Group comparisons were made with a chi-squared test for categorical variables; the Mann–Whitney
The response rates among skiers and in the reference group were 27% (
Demographic and clinical characteristics of Swedish cross-country skiers in early adolescence and a population-based reference group.
Cross-country skiers | References |
|
|||||
---|---|---|---|---|---|---|---|
All |
Boys |
Girls |
All |
Boys |
Girls | ||
Age, mean (SD) | 12.83 (0.69) | 12.73 (0.74) | 12.91 (0.63) | 13.64 (0.64) | 13.68 (0.68) | 13.59 (0.59) |
|
Self-reported asthma | 20 (23) | 9 (22) | 11 (24) | 36 (12) | 23 (14) | 13 (10) |
|
Current wheezing | 22 (25) | 13 (32) | 9 (20) | 42 (14) | 28 (18) | 14 (11) |
|
Wheezing without a common cold | 17 (20) | 10 (24) | 7 (15) | 27 (9) | 19 (12) | 8 (6) |
|
Exercise-induced wheezing | 18 (21) | 10 (24) | 8 (17) | 33 (11) | 22 (14) | 11 (8) |
|
Smoking in family | 0 (0) | 0 (0) | 0 (0) | 42 (14) | 20 (13) | 22 (17) |
|
BMI, median (IQR) | 19 (18–20) | 18 (18-19) | 19 (18–20) | 20 (18–22) | 20 (18–21) | 20 (18–22) |
|
Exercise (hours/week), median (IQR) | 6 (5–8) | 6 (5–8) | 6 (5–7) | 4 (3–7) | 5 (3–7) | 4 (2–6) |
|
Data are presented as
A description of and comparison between skiers and references with self-reported asthma are presented in Table
Comparison between subjects with self-reported asthma among Swedish cross-country skiers in early adolescence and in a population-based reference group.
Cross-country skiers | References |
|
|||||
---|---|---|---|---|---|---|---|
All |
Boys |
Girls |
All |
Boys |
Girls | ||
Current wheezing | 16 (80) | 9 (100) | 7 (64) | 25 (69) | 19 (83) | 6 (46) | 0.393 |
Wheezing without a common cold | 15 (75) | 9 (100) | 6 (55) | 16 (44) | 13 (57) | 3 (23) |
|
Exercise-induced wheezing | 14 (70) | 7 (78) | 7 (64) | 20 (56) | 14 (61) | 6 (46) | 0.289 |
Allergic rhinitis | 10 (50) | 7 (78) | 3 (27) | 21 (60) | 13 (59) | 8 (62) | 0.472 |
Parent or sibling with asthma | 12 (63) | 6 (67) | 6 (60) | 19 (54) | 11 (50) | 8 (62) | 0.529 |
Smoking in family | 0 (0) | 0 (0) | 0 (0) | 5 (14) | 2 (9) | 3 (23) | 0.076 |
SABA/LABA1 | 19 (95) | 8 (89) | 11 (100) | 36 (100) | 23 (100) | 13 (100) | 0.176 |
ICS2 | 13 (65) | 6 (67) | 7 (64) | 21 (58) | 14 (61) | 7 (54) | 0.625 |
ICS + LABA3 | 5 (25) | 1 (11) | 4 (36) | 7 (19) | 6 (26) | 1 (8) | 0.627 |
Other medication4 | 7 (35) | 2 (22) | 5 (45) | 5 (14) | 4 (17) | 1 (8) | 0.065 |
ACT score, median (IQR) | 21 (19–23) | 20 (18–21) | 23 (21–24) | 22 (19–24) | 22 (19–24) | 20 (20–23) | 0.535 |
BMI, median (IQR) | 18 (17–19) | 18 (18-19) | 19 (18–21) | 20 (19–21) | 20 (20-21) | 19 (18–21) |
|
Exercise (hours/week), median (IQR) | 6 (5–8) | 6 (6-7) | 5 (5–7) | 5 (4–8) | 7 (5–10) | 4 (3–6) | 0.678 |
Data are presented as
Among skiers (
Comparison between subjects with and without current wheezing among Swedish cross-country skiers in early adolescence and in a population-based reference group.
Cross-country skiers | References | |||||
---|---|---|---|---|---|---|
Current wheezing |
No current wheezing |
|
Current wheezing |
No current wheezing |
|
|
BMI, median (IQR) | 18 (18-19) | 19 (18–20) | 0.668 | 20 (20-21) | 20 (18–22) | 0.163 |
Exercise (hours/week), median (IQR) | 6 (5–7) | 6 (5–8) | 0.850 | 5 (3–8) | 4 (2–6) |
|
Self-reported asthma | 16 (73) | 4 (6) |
|
25 (60) | 11 (4) |
|
Parent or sibling with asthma | 13 (59) | 14 (22) |
|
20 (49) | 75 (31) |
|
Smoking in family | 0 (0) | 0 (0) | NA | 6 (14) | 36 (14) | 0.314 |
Data are presented as
In this cross-sectional postal survey among Swedish cross-country skiers in early adolescence, the prevalence of self-reported asthma and wheezing during the last 12 months was significantly higher than in a population-based reference group. The prevalence was close to twice as high among cross-country skiers (23% and 25% for self-reported asthma and wheezing, respectively), when compared to the reference group (12% and 14%, respectively).
Asthma among cross-country skiers has almost been considered an occupational disease [
Another explanation for the high prevalence of asthma among skiers is an increased awareness of asthma and the symptoms of asthma among athletes, their parents, coaches, and healthcare personnel. Additionally, it is possible that skiers have higher demands on their respiratory ventilation capacity and therefore experience more and tolerate fewer symptoms. This may also contribute to the fact that the skiers with asthma had more frequent contact with the healthcare than the reference group with asthma in our study.
The skiers in the present study largely fit into the characteristics of those with atopic asthma and do not provide support for the sports asthma phenotype hypothesis. The sports asthma phenotype, in contrast to atopic asthma, involves respiratory symptoms, physical activity, and the absence of allergies, has been suggested to be prevalent among winter and water sports athletes [
Overall, skiers reported more respiratory symptoms than the reference group, probably because the skiers had a higher prevalence of asthma, exercised more frequently, and perhaps had an increased exposure to subzero temperatures. Respiratory symptoms, in general, are very common during physical activity in cold temperatures [
It is worrying that being an early adolescent skier, even at exercise levels that do not reach the international and national guidelines of at least 60 minutes of pulse-raising activity each day [
It is a strength that our survey was based on well-validated questionnaires, ECRHS II and ISAAC [
To conclude, our hypothesis was confirmed by this Swedish postal questionnaire survey; the prevalence of asthma and respiratory symptoms among competitive cross-country skiers in early adolescence was higher than in a population-based reference group of similar ages. Even though the low response rate in the study is a limitation, the results are considered fairly representative and should be taken into account. The results indicate that preventive measures, such as more restrictions on exercise when the temperature is below a certain level, may be warranted among cross-country skiers in early adolescence. Furthermore, whether wearing breathing masks prevent or attenuate cold air-induced airway morbidity should be examined.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors report no conflicts of interest.
The authors would like to thank the county team coaches and the Swedish Ski Association for distributing the questionnaires and Anna Lindam, Statistician at the Department of Research and Development, Region Jämtland Härjedalen. The study was funded by Syskonen Perssons Donationsfond (JLL-458171) and Research & 209 Development Unit, Region Jämtland Härjedalen (JLL-561901).