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11-10-2011 | Immunology | Article

Ageing reduces allergy risk


Free abstract

MedWire News: Study findings suggest that the risk for allergic sensitization decreases with age.

This age-related risk reduction is most likely a feature of the natural aging process rather than a consequence of age-specific differences in lifestyle and living environment, say the researchers.

"Further longitudinal studies of a possible age effect on the dynamic process of allergic sensitization are of interest as birth cohorts with a high prevalence of sensitized subjects grow older," write Eva Rönmark (Umeå University, Sweden) and co-authors.

A family history of allergies, tobacco smoke exposure, and urban habitation in early childhood have been cited by many studies as risk factors for allergic sensitization. However, results indicating otherwise have been demonstrated by other studies.

Rönmark et al therefore devised the current study to analyze allergic sensitization prevalence trends among adults aged 20-60 years, over a 10-year period.

The study, published in the Journal of Allergy and Clinical Immunology, involved 664 randomly selected adults. All underwent skin prick testing (SPT), blood immunoglobulin (Ig) E measurement, and completed a questionnaire about their lifestyles and respiratory symptoms at baseline and at study end.

A positive SPT was approximately twice as common among young (20-29 years) compared with mature (50-60 years) participants throughout the study period, at respective rates of 55.3% and 26.0% at baseline, and 40.0% and 23.7% at study end.

Allergic sensitization determined by IgE measurement followed a similar trend to this SPT-related finding.

When risk factors for allergic sensitization were investigated, Rönmark and team observed that a family history of allergy increased an individual's risk for allergic sensitization approximately two fold. And increasing age showed significant negative association with allergic sensitization as did the presence of furry animals in the participant's home.

Among the 112 participants who had a positive SPT at baseline, 32% showed allergic sensitization remission, as determined by a negative SPT, by study end.

Of note, the remission of cat-related allergic sensitization was the commonest type of remission, occurring at a rate of 8.5%.

The analysis of baseline predictors of future remission of allergic sensitization revealed that the absence of childhood hayfever or allergic rhinitis increased the likelihood of remission by more than 12 fold compared with the presence of either condition. And participants aged 40-60 years had a three-fold higher likelihood of remission than those aged 20-39 years.

"In this longitudinal population-based cohort study, we found a low incidence and high remission of allergic sensitization explaining the decreasing prevalence of allergic sensitization with increasing age," say Rönmark and team.

They conclude that there is a need for "accurate screening for risk factors for a better understanding of trends in prevalence by age of allergic sensitization in the population."

By Lauretta Ihonor

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