WASHINGTON, DC—In addition to physical discomfort, untreated allergic rhinitis can cause decreases in vigilance, response time, and accuracy similar to those induced by sedating drugs. But these impairments appear to have less to do with actual allergy symptoms than with down-regulation of the central nervous system (CNS) during an allergic response. “Allergies have a broad effect on quality of life and the ability to think quickly,” said Jeffrey A. Wilken, PhD, Director of Neuropsychology at the VA Medical Center in Washington, DC.

Dr. Wilken and colleagues conducted a randomized parallel-group study—funded by Integrated Therapeutics Group—during the off-season for allergic rhinitis. Patients with a minimum two-year history of ragweed-associated allergic rhinitis were randomly assigned to one of two groups, one of which was exposed to ragweed pollen in an allergy exposure unit. The cognitive performance of the two groups was then compared.

TESTING COGNITIVE FUNCTION

All patients underwent a battery of cognitive tests at baseline. About three quarters of the patients (n = 234) were then exposed to ragweed pollen until they developed symptoms; the other 62 patients were not exposed to pollen and thus had no rhinitis symptoms. The cognitive tests were repeated six to eight days after baseline assessment in both groups after allergen priming to be sure that subjects in the exposed group still had symptoms. Vigilance, as determined by the Kay Continuous Performance Test (KCPT), was the primary end point. Other cognitive capabilities measured included working memory, reasoning, calculating, and psychomotor functioning. No patients received allergy medication during the study.

As expected, the patients exposed to ragweed pollen experienced significant increases in nasal, nonnasal, and “total” symptoms. They also experienced a significant rise in their self-reported level of sedation, greater drowsiness and lethargy, and decreased clear-headedness, attentiveness, coordination, and proficiency. Following allergen exposure, these patients performed markedly worse than did the nonexposed patients on all parameters of the KCPT. They also had lower scores on many of the measurements of cognitive function. The greatest effect of allergen exposure was seen on tests of working memory and psychomotor speed.

IMPAIRMENT UNRELATED TO SYMPTOMS

There was no correlation between the nasal signs and symptoms of allergic rhinitis and nonnasal changes in cognitive function. The changes in cognitive function appeared to be due to a depression of the CNS, such that the patients were performing slightly below their normal level. “Allergies cause somnolence, but it’s not the symptoms, it’s the effect of allergies on the CNS,” explained Dr. Wilken, who is also an Adjunct Professor of Psychology at the University of Maryland in College Park.

People with symptomatic allergic rhinitis may have lapses in attention and decreased reaction time when driving a car or operating machinery, even when not taking medications for their symptoms. In an office environment, people with symptomatic allergic rhinitis may be slower to complete tasks requiring calculations or verbal reasoning.

What can people with allergies do to avoid cognitive impairment? The answer seems obvious. “People need to treat their allergies with nonsedating, second-generation antihistamines,” said Dr. Wilken. However, he added, “Most people are notoriously bad at reporting their own cognitive function.” Although they may say they have no allergy-related impairment, “the truth is that most people will experience the decrements in vigilance that we observed in our study.”

Dr. Wilken noted that the detrimental effect of allergies on cognition is a relatively new observation that few people are aware of. “Past studies either did not use particularly sensitive measures of cognitive function or didn’t study the right population,” he said. “This study is one of the first to show a global effect on awareness.”

—Gale Jurasek