The following originally appeared on The Upshot (copyright 2017, The New York Times Company)
This is the time of year my kids and I have seasonal allergic rhinitis, better known as hay fever. I’d always thought it was merely a nuisance, but it turns out it also degrades cognitive performance, at least a little.
Hay fever affects at least 10 percent of the population, and a higher percentage of children. The most obvious signs of allergic response include sneezing, itching and a runny nose. These can disrupt sleep, leading to fatigue, and the allergy can cause neurocognitive deficits we may not notice in ourselves or in our children. Medications used to treat the allergy can also induce sleepiness in some people.
In the United States, school-age children collectively lose about two million school days because of pollen allergies. Even when they attend school, allergy-suffering students may perform a bit worse than their nonallergic counterparts.
Using data from Norway, a recent study shows that when pollen levels rise, students’ test scores fall. The study used data from nearly 70,000 high school exit exams, which Norwegian students must pass to graduate and are used for higher education placement. Students take exams at different locations, and each student takes several at different times of year, providing multiple data points per student.
The study’s author, Simon Bensnes, a Ph.D. candidate in the Department of Economics at the Norwegian University of Science and Technology, combined these with pollen count data linked to the location and time at which each student took each exam, as well as other demographic and air-quality data used to control for potentially confounding factors.
Pollen counts are measured in grains of pollen per cubic meter of air and can be as high as the 100s at the height of pollen season in Norway. For students allergic to pollen, Mr. Bensnes found that a pollen count increase of 37 — large enough to cause symptoms in highly allergic people — is associated with a drop of about one-tenth of a point in exam scores. The scores range from one (worst performance) to six (best performance).
Does such a seemingly small effect matter in the long run? Other results suggest they do. The study also finds that higher pollen counts correlate with a slightly lower likelihood of enrolling in a university and a lower probability of going into a STEM field. However, though the statistical methods to analyze test scores are rigorous enough to reasonably infer they’re causal, the ones for these longer-term results are less so.
Still, Mr. Bensnes said, “it would be surprising if there were no effects in the longer run.” This is particularly likely in countries where exams are weighed more heavily than in Norway toward entrance to institutions of higher education. There, exams count only for about 15 percent of entrance determinations.
Norway is not the only setting where a pollen-exam relationship has been found. In Britain, students take an exit exam at the end of secondary education in the spring or summer, when pollen counts are high. They also take a practice test the prior winter. Researchers found that compared with those with no allergy symptoms, British students who report allergies or take allergy medications during their secondary education exit exams are 40 percent to 70 percent more likely to score a full grade lower than they did on their practice test.
A study in the United States found that a doubling of the pollen count is associated with about 1 or 2 percent drop in the proportion of third graders passing English and math achievement tests.
Clinical studies have examined the cognitive effects of hay fever more directly. For example, a study found that people with hay fever experienced slower speeds of mental processing during ragweed season than at other times of year. Another study exposed allergic people to pollen in a controlled setting. It found that they exhibited slower mental function, decreased memory, and poorer reasoning and computation abilities compared with nonallergic test subjects.
More generally, what we breathe affects how well we perform at school or work. Several studies found a link between air pollution and school absences, as well as labor supply and worker productivity. Worse air quality can cause or worsen respiratory problems, like asthma, reducing some children’s ability to attend school and adults’ entry into the work force. It can also harm job performance.
One study found that higher concentrations of certain air pollutants hurt test scores of Israeli students and the chances of passing a high school exam necessary for higher education.
Individually, we may not be able to do much about air pollution, but we can try to reduce the impact of pollen on school and work performance. Finding allergy medication that doesn’t induce drowsiness is an obvious approach. When it comes to high-stakes exams, it may be worth choosing test dates outside the allergy season, if possible. Hay fever is rarely debilitating, but its small effects can put us off our best game.