Literature / Littérature scientifique

CJRM 2000;5(3):163-5

Occasionally a number of articles surface, apparently coincidentally on a similar topic, and a theme emerges. Inevitably, further research turns up even more information, though the reader is cautioned that these excursions into the literature are by no means comprehensive and may be incomplete. That said, here are some newly reported findings on asthma in rural areas.

Relative scarcity of asthma and atopy among rural adolescents raised on a farm. Ernst P, Cormier Y. Am J Respir Crit Care Med 2000;161(5):1563-6.

Canadian rural students aged 12-19 who had been raised on a farm were compared to a group "without regular exposure to a farming environment," with respect to symptoms of asthma, results of allergy skin tests and response to bronchoprovocation with methacholine. Investigators found a significantly lower prevalence of asthma, far less airway hyper-responsiveness and many fewer positive skin tests among adolescents raised on a farm than among non-farm teenagers. The differences were especially pronounced in girls.

They felt the most likely explanation for these findings was that the rural farm environment led to exposure, from a very early age, to a varied and complicated blend of irritant, allergenic and infectious agents.

These findings are similar to a number of other recent reports:

Farm environment in childhood prevents the development of allergies. Kilpelainen M, Terho EO, Helenius H, Koskenuvo M. Clin Exp Allergy 2000;30(2):201-8.

Austrian children living on a farm have less hay fever, asthma and allergic sensitization. Riedler J, Eber W, Oberfeld G, Schrever M. Clin Exp Allergy 2000;30(2):194-200.

Reduced risk of hay fever and asthma among children of farmers. Von Ehrenstein OS, Von Mutius E, Illi S, Baumann L, Bohm O, von Kries R. Clin Exp Allergy 2000;30(2):187-93.

Does this translate into less work for rural docs? It seems that this bit of good news is countered to some extent by a continuing occupational risk encountered mainly by rural adults, particularly farmers, and expressed often as morbidity in older age groups.

Asthma management in rural Australia. Watts RW. Aust J Rural Health 1999;7(4):249-52.

In this review the author concluded that morbidity from asthma in rural Australia (as expressed by hospital separations) was overall quite similar to urban Australia, although this was the result of over-representation in the over 65 age group and under-representation (similar to the above) in the 0-14 age group.

Health service accessibility and deaths from asthma in 401 local authority districts in England and Wales, 1988-92. Jones AP, Bentham G. Thorax Mar 1997;52(3):218-22.

These authors examined the relationship of mortality to distance from acute care facilities. They found that lack of access to a car was significantly associated with mortality and that "there was a tendency for mortality to rise with increasing distance from the hospital, with a relative risk of 1.01 for an increase in distance of one kilometer."

Lastly, a longitudinal study in Sweden suggests that prevalence of asthma among dairy farmers is increasing.

Increasing prevalence of asthma over 12 years among dairy farmers on Gotland, Sweden: storage mites remain dominant allergens. Kronqvist M, Johansson E, Pershagen G, Johansson SG, van Hage-Hamsten M. Clin Exp Allergy 1999;29(1):35-41.

These authors conducted a follow-up study of symptoms, working conditions and smoking habits in 1577 Swedish farmers aged 15-65, of whom 1015 were dairy farmers. A representative subgroup (461) underwent a skin-prick test and RAST analysis. The prevalence of asthma had increased from 5.3% to 9.8%, and this was accompanied by a prevalence of storage mite allergy of 6.5%. These mites remain "dominant allergens for developing allergic disease."

© 2000 Society of Rural Physicians of Canada