4/1/03 Cognitive effects of allergic rhinitisSummarySome patients with allergic rhinitis (AR) describe systemic symptoms such as grogginess, and decreased cognitive functions not explainable by the effects of any medication taken for AR. Wilken et al of the VA Medical Center in Washington, DC investigated this matter in a randomized, parallel-group study of 234 individuals with well-documented, ragweed-induced seasonal AR who were studied outside the relevant pollinating season. Following baseline cognitive studies, 75% of the group was exposed to ragweed pollen in a pollen exposure unit until AR nasal symptoms occurred. The other 25% of the group had a sham exposure without symptoms induced. The cognitive tests were then repeated 6-8 days later, following an allergen priming exposure. No allergy medication was taken by any subject. Those exposed to ragweed experienced a significant increase in self-reported levels of sedation, greater drowsiness, decreased attentiveness, coordination and proficiency. They performed markedly worse on the Kay Continuous Performance Test and had lower cognitive function, particularly in tests of working memory and psychomotor speed. There was no correlation between the intensity of nasal symptoms and the decrease in cognitive function in individual subjects. Therefore, the authors concluded that the cognitive effects were due to a direct depressive effect of the allergic reaction in the central nervous system. Reference - Ann Allergy Asthma Immunol 2002;89:372-380 Editor's Comments My impression is that prominent acute flare of AR are often accompanied by systemic subjective symptoms such as itching of the body, particularly the palms, small of back and sometimes other areas. Some individuals also describe being "out of sorts" with lethargy, difficulty in concentration, memory or calculating capacity. It has been assumed that such decreased cognitive function was due, at least in part, to decreased or poor sleep occasioned by the respiratory problems in AR. It is well known that histamine released in prominent allergic reactions can act as a neurotransmitter (binding to a distinct receptor called H3 receptor in the CNS?). Therefore, it is certainly conceivable that cognitive effects can occur in prominent allergic reactions. The authors recommend use of non-sedating antihistamines (e.g. - fexofenadine) for such non-respiratory symptoms in AR, This is certainly a reasonable suggestion, although I am not sure whether the effect of non-sedating antihistamine agents on such cognitive dysfunction has been studied in a controlled manner.
|
