Children who live in colder, wetter areas are at greater risk of suffering the condition because they have fewer hours of sunlight, according to a new study.
People with asthma have been found to have lower levels of vitamin D which is produced by exposure to sunlight.
“Prolonged exposure to the sun can cause cancer, but it’s also dangerous to avoid it.
“There has to be a balance between the pros and cons,” says Alberto Arnedo-Pena, an epidemiologist lead author of research, which is part of the International Study of Asthma and Allergies in Childhood (ISAAC) at the University of Murcia in Spain.
“In fact, 90% of our vitamin D is synthesised through exposure to the sun.
“This vitamin, which can be found in various cell receptors, is usually found at lower levels in people with asthma.
“The study results show that there is a higher prevalence of this illness among children in wetter places with less sun.”
The research, carried out on more than 45,000 children and teenagers from nine Spanish cities and published in the International Journal of Biometeorology, shows that climatic conditions, above all solar radiation, can in many cases explain the high geographical variation in the prevalence of asthma in Spain.
In northern countries (where there are fewer hours of sunshine than in the Mediterranean), the advice is to spend 20 to 30 minutes’ in the sun each day.
This should not be done at times within the highest risk period – from noon to 4pm.
“There is a problem in countries at latitudes higher than 40º north, where it is not possible to absorb enough vitamin D during the winter months.
“People in these countries should take supplements to ensure they are not at risk,” the researcher concludes.