The prevalence of asthma in cross-country skiers is 21 %, which is higher than that in the general population. |
There is an indication that asthma is underdiagnosed among skiers, especially during the previous decades, as many skiers without previous diagnosis of asthma or asthma medication fulfilled criteria for asthma according to lung function tests. |
There is a need for international consensus over the criteria of asthma and its treatment in athletes to avoid both over and under diagnosis of asthma. |
The usual onset age of asthma in cross-country skiers is 10–17 years of age, which is different from that in the general population, for whom the onset more often occurs in early childhood. |
The prevalence of asthma and use of asthma medication (21 % vs. 23 %) were similar, suggesting that there is no remarkable overuse of asthma medication among skiers. However, the data is limited on the use of asthma medication in skiers without diagnosis of asthma. |
Asthma in skiers seems to be less often eosinophilic and more often neutrophilic compared to asthma in non-skiers. |
Due to the high prevalence of asthma in cross-country skiers, regular screening of asthma-like symptoms and lung function could be beneficial to competitive skiers. |
1 Introduction
2 Methods
2.1 Literature search
2.2 Study inclusion
2.3 Data extraction
2.4 Quality appraisal and data analyses
3 Results
3.1 Prevalence of asthma-related symptoms
3.2 Prevalence of asthma
3.2.1 Studies reporting prevalence of self-reported physician-diagnosed asthma
Year | Author and country | Participants | Sex and age | Diagnostic criteria | Self-reported physician-diagnosed asthma | Risk of bias |
---|---|---|---|---|---|---|
1994 | Larsson et al. Sweden [20] | 299 cross-country skiers from upper secondary schools, national ski teams and the Swedish army; 127 controls from same upper secondary schools | 172 M, 127 F, age 18.5 ± 2.4 years (mean) | Yes to question "Do you have asthma diagnosed by a physician?" | 15% in skiers, 6% in controls | Low |
1994 | Heir and Oseid, Norway [21] | 153 elite cross-country skiers, 241 controls matched for age, sex and home municipality | 106 M, 47 F, age 25.5 years (mean) | Subject reporting asthma diagnosed by physician | 14.4% in skiers, 5.0% in controls (p = < 0.01) | Low |
2004 | Langdeau et al. Canada [24] | 20 cross-country skiers and 6 biathletes in Quebec | Cannot be extracted | Subject reporting self-reported asthma and/or physician-diagnosed asthma | 15.3% (cross-country skiing and biathlon combined) | Moderate. Small sample size |
2015 | Norqvist et al. Sweden [26] | 236 cross-country skiers or biathletes in upper secondary schools, junior and senior national ski teams or universities | Upper secondary school 17 (15–19), national teams 24 (18–34), university athletes (23 (19–31), mean and (range) | Yes to both of the following questions: "Have you ever had asthma?" "Was it diagnosed by a doctor?" | 30.9% | Low |
2018 | Eklund et al. Sweden [27] | 244 cross-country skiers, biathletes and ski-orienteers in upper secondary schools | 127 M, 117 F, age 16.8 ± 1.2 y | Yes to both of the following questions: "Have you ever had asthma?" "Was it diagnosed by a doctor?" | Total 27%, males 20%, females 34%, controls 19% | Low |
3.2.2 Studies reporting prevalence of asthma based on current lung function measures
Year | Author and country | Participants | Sex and age | Diagnostic criteria | Physician-diagnosed asthma | Risk of bias |
---|---|---|---|---|---|---|
2012 | Turmel et al. Canada [25] | 34 cross-country skiers and 10 biathletes | 29 M, 15 F | ≥ 12% FEV1 improvement after β2-agonist and/or the presence of airway hyperresponsiveness to EVH or methacholine challenge (≤ 4 mg/ml or ≤ 16 mg/ml with active inhaled corticosteroid treatment) and asthmatic symptoms | 20% | Moderate. Possible selection bias. Although reversibility was included in the criteria of asthma, only AHR was tested for |
Year | Author and country | Participants | Sex and age | Diagnostic criteria | Total asthma prevalence | Risk of bias |
---|---|---|---|---|---|---|
1993 | Larsson et al. Sweden [19] | 42 cross-country skiers in Stockholm and Östersund | 36 M, 6 F, age 24 years (mean) | BHR to methacholine and two asthma-like symptoms OR a previous diagnosis of asthma with active asthma medication use | 55% | Moderate. The subjects may not represent the whole skier population well due to the recruitment methods. Methacholine challenge test not identical in different locations |
1996 | Sue-Chu et al. Norway and Sweden [22] | 118 cross-country skiers in senior secondary school in Norway, 38 cross-country skiers in senior secondary school and 15 skiers serving as conscripts in Sweden | Norway 90 M 28 F, age 17.0 ± 1.1 years, Sweden 36 M 17 F, age 18.4 ± 1.4 years | Total cases of asthma defined as current asthma cases or physician-diagnosed asthma cases currently treated with steroids | Norway: 12% Sweden: 42% | Low |
2002 | Michalak et al. France [23] | 180 cross-country skiers or biathletes | 121 M 59 F, age 18 ± 2 years (mean) | Increase in FEV1 by ≥ 12% or 200 ml in the bronchodilation test or self-reported physician-diagnosed asthma | 14% | Low |
2012 | Turmel et al. Canada [25] | 34 cross-country skiers and 10 biathletes | 29 M, 15 F | ≥ 12% FEV1 improvement after β2-agonist and/or the presence of airway hyperresponsiveness to EVH or methacholine challenge (≤ 4 mg/ml or ≤ 16 mg/ml with active inhaled corticosteroid treatment) and asthmatic symptoms | 30% | Moderate. Possible selection bias. Although airway reversibility was included in the criteria of asthma, only AHR was tested for |
3.2.3 Studies reporting prevalence of asthma based on combined criteria of previous physician-diagnosed asthma or current lung function measures
3.3 Possible underdiagnosis of asthma among skiers
3.4 Risk factors and onset age of asthma or asthma-related symptoms
3.5 Use of asthma medication among skiers
Year | Author and country | Participants | Sex and age | Use of asthma medication in skiers | Use of asthma medication in controls | Risk of bias |
---|---|---|---|---|---|---|
1993 | Larsson et al. Sweden [19] | 42 skiers and 29 controls | 36 M, 6 F, age 24 years (16–50 years) | 36% 15/42 | 0%, healthy controls recruited | Moderate. Small sample size |
1994 | Larsson et al. Sweden [20] | 299 cross-country skiers from upper secondary school, national ski team and Swedish army. 127 controls from same upper secondary schools | 172 M, 127 F, age 18.5 ± 2.4 years (mean) | 18% | 7% | Low |
1994 | Heir and Oseid, Sweden [21] | 153 elite cross-country skiers, 241 controls matched for age, sex and home municipality | 106 M, 47 F, age 25.5 years (mean) | 22.2% (34/153, 25 regularly, 9 occasionally) | 4,6% (11/241, 7 regularly, 4 occasionally) | Low |
1996 | Sue-Chu et al. Norway and Sweden [22] | 118 cross-country skiers in senior secondary school in Norway, 38 skiers in senior secondary school and 15 military conscripts in Sweden | Norway 90 M 28 F, age 17.0 ± 1,1 years, Sweden 36 M 17 F, age 18.4 ± 1,4 years | Total 23% (Sweden 38%, Norway 16%); β2-agonist 21% (38 SWE, 14% NOR), ICS (inhaled corticosteroids) 10% (SWE 23%, NOR 4%) | No controls | Low |
2015 | Norqvist et al. Sweden [26] | 237 cross-country skiers or biathletes in upper secondary schools, junior and senior national ski teams or universities | Upper secondary school 17 years (15–19), national teams 24 years (18–34), university athletes (23 (19–31), mean and (range) | 15–19 years 25%, 16% M, 35% F (p = 0.005); 20–34 years 28%, 18% M, 38% F (p = 0.061); total 26% | No controls | Low |
2018 | Eklund et al. Sweden [27] | 244 cross-country skiers, biathletes and ski-orienteers in upper secondary schools | 127 males, 117 females, age 16.8 ± 1.2 years | 22% (14% M, 23% F) (last 12 mo) (p 0.003) | Total 11% (p = 0.03 compared to skiers), 8% M, 14% F | Low |
3.6 Asthma-related pathophysiological features in skiers
3.6.1 Airway inflammation
Year | Author | Subjects | Protocol | Main finding | Risk of bias |
---|---|---|---|---|---|
1998 | Sue-Chu et al. [14] | 44 skiers and 12 healthy controls. 59% of the skiers had asthma-like symptoms and were hyperresponsive to methacholine | Bronchial biopsy from second and third generation carinae | Lymphoid aggregates in skiers 64% vs. 25% in controls | Low |
1999 | Sue-Chu et al. [28] | 30 skiers and 10 healthy controls. 63% of the skiers were hyperresponsive to methacholine, and 40% were hyperresponsive and had asthma-related symptoms | Bronchial biopsy and bronchoalveolar lavage | Macroscopic inflammatory index based on the visual evaluation of bronchial mucosa was significantly higher in skiers than in controls (3.1 vs. 1.3, p = 0.008). Subjects with “ski asthma” had higher percentages of lymphocytes and lower percentages of macrophages in BAL fluid compared with healthy controls, but these results were not significantly different from those of healthy skiers | Low |
1999 | Sue-Chu et al. study 2 [29] | 44 skiers, 29 mild asthmatic controls and 82 healthy controls. Nine skiers were hyperresponsive to methacholine and had asthmatic symptoms | Exhaled nitric oxide concentration at rest. Expiratory flow rate was set to 250 ml per second | Exhaled nitric oxide concentrations were not different compared to healthy controls (6.5 vs. 5.2 ppb), but asthmatic controls had threefold higher levels compared to skiers (6.5 vs. 19.2 ppb, p < 0.01). The atopic skiers had twofold greater exhaled nitric oxide concentrations compared to non-atopic skiers (values not available) | Low |
2000 | Karjalainen et al. [15] | 40 skiers with no prior diagnosis of asthma, 12 asthmatic controls and 12 healthy controls. 75% of the skiers were hyperresponsive to methacholine and 53% were hyperresponsive and had asthma-related symptoms | Bronchial biopsy from second and third generation carinae | Skiers had higher counts of T-lymphocytes, macrophages and eosinophils compared with controls. the counts of macrophage, mast cell and eosinophil cell counts were significantly lower in skiers compared to asthmatic subjects, but neutrophil count was significantly higher in skiers compared to asthmatic controls. Tenascin thickness in subepithelial basement membrane was significantly thicker in skiers compared to healthy controls but in nonhyperresponsive skiers the tenascin thickness was lower compared to patients with asthma | Low |
2014 | Zebrowska et al. [37] | 12 elite female cross-country skiers | Exhaled nitric oxide concentration at rest | Exhaled nitric oxide concentrations were reported to be within a normal range (18.7 ± 4.8 ppb) | High. Selective reporting and measurement times not reported. Possible asthma medication use not reported |
2018 | Stang et al. [39] | 10 skiers and 10 swimmers with previous asthma diagnosis, 9 skiers and 10 swimmers with no previous diagnosis of asthma, 24 healthy controls | FeNO, spirometry, skin prick test, methacholine challenge, induced sputum | Most results of the skiers were pooled together with the results of the swimmers. Although the results of the skiers were not explicitly analyzed separately, it seemed that there were no significant differences in the levels of inflammatory cells or mediators induced between the asthmatic skiers, healthy skiers and non-athletic controls | Moderate. Only the results of the sputum samples were separately reported in skiers, and there was no statistical analysis |
3.6.2 Seasonal variation in bronchial reactivity or airway inflammation
3.7 Effect of anti-asthmatic treatment in non-asthmatic and asthmatic skiers
3.8 Other asthma-related studies in cross-country skiers
Year | Author | Subjects | Protocol | Main finding | Risk of bias |
---|---|---|---|---|---|
2000 | Wilber et al. USA [31] | 34 biathletes and 14 cross-country skiers participating in Olympic trials | The incidence of EIB in qualified Olympic athletes by spirometry after Olympic trial race (FEV1 ≥ 10%) | In the qualifying Olympic team, no biathletes had EIB, 57% of female and 43% of male cross-country skiers had EIB | Moderate. The results are represented as subgroup analysis from qualified Olympic athletes and the number of athletes is not reported |
2010 | Sue-Chu et al. Norway [35] | 58 cross-country skiers (18.1 yrs), 10 skiers with prior asthma diagnosis | Airway hyperresponsiveness to methacholine (PD20 ≤ 1814 μg), AMP (adenosine 5-monophospate, ≤ 50.5 mg), mannitol (≤ 635 mg), 8 min EVH test and 4.7 km field exercise challenge (≥ 10% FEV1 decrease at two consecutive time points) | Heterogenous responsiveness to different stimuli among skiers Among 58 skiers40% had positive methacholine test, 9% had positive AMP test, and 5% had positive mannitol test Among 33 skiers 9% had a positive EVH test, and 18% had a positive field exercise challenge | Moderate (the authors own stock) |
2007 | Stensrud et al, Norway [34] | 24 Norwegian national cross-country team skiers | Spirometry after cross-country ski race (≥ 10% FEV1), methacholine challenge (PD20 ≤ 1600 μg = 8 μmol) | After a ski race 8% of the skiers had bronchial obstruction. 38% had a positive methacholine test | Low |
2010 | Stenfors, Sweden [56] | 46 cross-country skiers or biathletes on national or international level | Multiple self-reported symptoms compared to bronchial hyperresponsiveness in methacholine or mannitol challenge and EVH | Self-reported symptoms had reasonable negative predictive values but very low positive predictive values in relation to bronchial hyperresponsiveness | Low. The sensitivities and specificities of the questions are not analyzed separately in those with and without known asthma or asthma medication |
2004 | Verges et al. France [45] | One female 19 years, and two male cross-country skiers 21 and 22 years of age and one unreported skier | Follow-up study 9–12 years with intermittent lung function tests, including spirometry and methacholine challenge | Three reported athletes developed objective signs of variable airway obstruction but tests were not systematically positive | Low |