(NEXSTAR) – A small study of COVID “long haulers” — those who experience longterm symptoms of the virus even after it is out of their systems — found that “brain fog” is a common, persistent symptom of the syndrome.

The study, published Tuesday in the Annals of Clinical and Translational Neurology, looked at a small sample size — just 100 people who visited one clinic — and found that the vast majority of COVID long haulers presented a myriad of neurological symptoms, even after the virus’ antibodies were no longer in their bodies.

The study also found that participants experienced fatigue that made daily life tasks difficult.

The most common neurologic symptoms were brain fog (81 percent), headaches (68 percent), numbness/tingling (60 percent) and changes in taste/smell (59 percent).

The most-reported non-neurologic symptoms included fatigue, depression/anxiety, shortness of breath and chest pain.

What’s especially alarming about the study is that the “vast majority” of the patients never experienced severe enough COVID-19 symptoms to require hospitalization, meaning even minor cases of COVID-19 can lead to longterm impacts.

The study furthermore shines light on the little-understood phenomenon of “long COVID” — a syndrome that has been widely reported but only minimally comprehended.

Even the definition of long COVID “is not settled,” though the study classifies COVID long haulers as those with “symptoms lasting more than six weeks.”