As if the headaches and stuffy nose aren't bad enough, chronic sinus trouble often leaves patients foggy-headed and depressed. Now, new research suggests one possible reason why: Sinusitis may trigger changes in brain activity.

"Chronic sinusitis is incredibly common," said study lead author Dr. Aria Jafari. Upwards of 11% of all Americans are affected, added Jafari, an assistant professor with the University of Washington Sinus and Skull Base Center, in Seattle.

The condition occurs when sinus tissue becomes swollen or inflamed because of an infection or perhaps an allergic reaction. Over time, the inflamed tissue thickens, much like calloused skin, the study authors explained.

Those who develop problems with concentration and thinking may find their quality of life undermined, Jafari said.

For this study, "we set out to determine if there are brain changes that can explain what we see in the clinic in our patients with sinusitis," he said.

The study team pored over brain scans and mental health assessments of more than 1,200 adults (aged 22 to 35). All had participated in the Human Connectome Project between 2019 and 2020.

From this pool, investigators zeroed in on 22 patients with moderate-to-severe sinus inflammation and 22 without sinus problems. Initially, the team saw no appreciable differences in terms of how well the patients fared on thinking tests, relative to those without sinusitis.

However, after further analyzing brain scans of this particular group, they discovered that a major functional hub — the frontoparietal network — was disrupted in cases of sinus inflammation.

"This brain area is important in coordinating the activity of several brain areas and maintaining balance in the brain," Jafari said. He noted that the area seemingly affected by sinus inflammation largely overlaps with those brain regions that are affected by mental illnesses, such as depression and schizophrenia, "both of which are surprisingly common among sinusitis patients."

Jafari suggested the finding is important because it may broaden the way clinicians view sinusitis.

"The acknowledgment of the brain dysfunction dimension of sinusitis by doctors is a powerful first step in treating the entire disease, not just the classic symptoms," he said.

"With improved awareness, the research will follow," Jafari added. "In the future, therapies focusing on brain dysfunction may be an option to help sinusitis patients regain their health and maximize their quality of life."

Still, the findings are preliminary and do not show a direct cause-and-effect relationship.

For the moment, many questions remain.

For example, could it be that sinus inflammation actually predisposes patients to develop mental illness? "This is a topic we hope to soon explore," Jafari said.

Dr. Stanley Goldstein is director of both Allergy and Asthma Care of Long Island and Island Medical Research in Rockville Centre, N.Y.

"We really don't know what's going on," said Goldstein, who was not involved in the study.

"I do see plenty of people with sinusitis that complain of what they describe as headaches, or some kind of pressure in the head. Something going on in the brain, so to speak," he said.

"I can't speak to a neurological point of view," Goldstein stressed. "But yes, maybe sinusitis patients have some kind of predisposition to the brain-fog issue. Maybe it's somehow related to localized inflammation."

But for the moment, he reiterated, "we just don't know."

The study was published online recently in JAMA Otolaryngology-Head & Neck Surgery.