Intense training linked to increased risk of asthma in cross-country skiers


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An intensive training regimen is linked to an increased risk of non-allergic asthma in competitive cross-country skiers, according to a study published in the open-access journal BMJ Open Sports and Exercise Medicine.

The prevalence of non-allergic asthma was highest among top-performing skiers, suggesting that it does not appear to hinder competitive chances.

Non-allergic asthma has been associated with respiratory tract infections, long-term exposure to irritants, and airway damage. It is relatively rare in childhood and early adulthood, becoming more common in old age.

Cross-country skiers are twice as likely to develop asthma as the general population, with symptoms typically beginning in early adolescence. Although the risk factors for allergic asthma are well known, those for the different types of non-allergic asthma are not as clearly defined.

The researchers wanted to assess the relative proportions of allergic and non-allergic asthma in competitive cross-country skiers compared to the general population. And they wanted to know what impact performance level and training intensity might have.

They invited all Finnish cross-country skiers who had entered either the national championships (from 17 years old) or the biggest national junior ski competition Hopeasompa (13-16 years old) to complete a questionnaire on the development of asthma.

Of a total of 1282 competitive skiers, 351 responded. They were matched by age, gender and geographic region with 338 people who were not cross-country skiers.

Current asthma was defined as experiencing at least one of the following: three asthma-related symptoms among cough, chest pain, shortness of breath, wheezing, or phlegm; active use of any asthma medication or an Asthma Control Test (ACT) score of less than 25 points indicating good asthma control.

Asthma was defined as allergic if the respondent had been diagnosed by a physician and exposure to furry animals or pollen caused asthma-related symptoms. Otherwise, asthma was defined as non-allergic.

The success of the skiers was evaluated according to the number of International Ski Federation (FIS) points accumulated for the 2018-19 season in effect at the time of the study. The fewer FIS points the skier obtains, the better his performance.

Some 189 of the skiers had been diagnosed or tested for asthma, and 91 had current symptoms. This compares to 69 of the non-skiers, 31 of whom had current symptoms. More skiers used medication to control their asthma: 123 versus 39.

About a third (36) of the 91 skiers with current asthma symptoms had allergic asthma, compared with 19 of the 31 non-skiers. But more than half of skiers (55) with current symptoms had non-allergic asthma, compared with 12 of non-skiers.

The difference in the prevalence of non-allergic asthma between the two groups was significant (60% vs. 39%), from the age of 14 years. No such difference was observed in the prevalence of allergic asthma between the two groups.

Cross-country skiers were almost 3.5 times more likely to have asthma, almost twice as likely to have allergic asthma, but more than 5 times more likely to have non-allergic asthma than non- skiers.

In both groups, parental or sibling asthma and allergic rhinitis were strongly associated with current asthma. But sporting success and training hours also had an influence.

A total of 163 (46%+) skiers participated in FIS competitions. Asthmatic skiers had fewer FIS points than non-asthmatic skiers: 173.22 versus 213.65.

And among the most successful skiers, those with the fewest FIS points, the prevalence of asthma was the highest (56%) with 65% of them non-allergic. This group was also the oldest and most trained.

Training for 100 hours or more each year was associated with a 35% higher risk of non-allergic asthma compared to an 18% higher risk of allergic asthma.

This is an observational study, and as such cannot establish cause. And despite being the largest survey of cross-country skiers of its kind, response rates have been relatively low, the researchers acknowledge.

Much of the information provided was also based on recall and subjective assessment of symptoms.

But: “Before starting their skiing career, there was no difference in the prevalence of asthma between cross-country skiers and [comparison group]and the [comparison group] mainly suffered from allergic asthma,” they point out.

“We conclude that the excess prevalence of asthma in competitive cross-country skiers compared to that of the general population is mainly due to the onset of non-allergic asthma a few years after the start of a skiing career. asset.”

And they explain: “Current findings suggest that intensive cold air training is the trigger for excess non-allergic asthma in skiers.

“This relationship between heavy training and non-allergic asthma may be related to airway damage caused by cold air, as airway damage has been suggested as one of the risk factors for asthma. not allergic.”

Allergic diseases increase the risk of asthma in adulthood

More information:
High training volume is associated with an increased prevalence of non-allergic asthma in competitive cross-country skiers, BMJ Open Sports and Exercise Medicine (2022). DOI: 10.1136/bmjsem-2022-001315

Provided by British Medical Journal

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