Can Intensive Training Lead to Increased Asthma Risk?

The researchers wanted to gauge the relative proportions of allergic and non-allergic asthma among competitive cross-country skiers compared with the general population. And they wanted to find out what impact performance level and training intensity might have.

They invited all Finnish cross-country skiers who had enrolled in either national championships (from the age of 17 onwards) or the largest national junior skiing Hopeasompa competition (13-16 year olds) to complete a questionnaire on asthma development.

Non-Allergic Asthma In Cross-Country Skiers

Out of a total of 1282 competitive skiers, 351 responded. They were matched for age, gender, and geographical region with 338 people who weren’t cross-country skiers.

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

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

Skiers’ success was assessed 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 is awarded, the better his/her performance is ranked.

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

Around 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 the skiers (55) with current symptoms had non-allergic asthma compared with 12 of the non-skiers.

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

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

In both groups, asthma in parents or siblings and allergic rhinitis were strongly associated with current asthma. But sporting success and training hours were also influential.

In total, 163 (46%+) skiers had participated in FIS competitions. Skiers with asthma had fewer FIS points than those without asthma: 173.22 vs 213.65.

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

Training for 100 or more hours every year was associated with 35% greater odds of non-allergic asthma compared with 18% greater odds of allergic asthma.

This is an observational study, and as such, can’t establish cause. And although the largest survey of cross-country skiers of its kind, the response rates were relatively low, acknowledge the researchers.

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

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

“We conclude that the excess prevalence of asthma among competitive cross-country skiers compared with that in the general population is mainly because of non-allergic asthma emerging a couple of years after the onset of an active skiing career.”

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

“This relation between intensive training and non-allergic asthma might be related to airway damage caused by cold air because airway damage has been suggested as one of the risk factors for non-allergic asthma.”

Source: Eurekalert