A new scientific review has found a direct link between specific immune markers and brain function, offering an explanation for the brain fog and memory problems many people experience after an illness.
The systematic review, published in Neuroscience & Biobehavioral Reviews, analyzed 32 studies involving 25,325 participants. Researchers found that certain immune markers are linked to how well the brain performs on tasks involving memory, processing speed, and mental flexibility.
Immune markers linked to cognitive decline
The immune system uses chemical messengers called cytokines to coordinate the body’s response to infections, injuries, and stress. When certain pro-inflammatory cytokines stay elevated for too long, they can affect the body beyond fighting off illness.
Three pro-inflammatory cytokines were identified as particularly problematic for brain function. IL-6 (interleukin-6) was linked to impairments in memory and slower processing speed. TNF-α (tumor necrosis factor-alpha) was linked to reduced cognitive performance. IFN-γ (interferon-gamma) was connected to struggles with memory tasks.
The researchers also found that elevated levels of CD14+CD16+ intermediate monocytes, a specific type of immune cell, correlated with slower processing speed and reduced mental flexibility. The brain has a harder time thinking quickly and adapting to new information when these inflammatory markers are high, which often happens during and after an illness.
Viral infections and brain function
The connection between inflammation and cognition was not limited to a single virus. The review included studies on SARS-CoV-2, HIV, herpes viruses, hepatitis, and Epstein-Barr virus. The patterns held across all of them. The cognitive effects of immune activation appear to be a shared feature of how the body responds to all viral threats.
Protective factors for brain function
The immune system also has built-in protectors for the brain. The study showed that IL-10, an anti-inflammatory cytokine, supports executive function and memory performance. IL-10 helps calm the immune response and creates a more favorable environment for cognitive function.
Higher levels of CD4+ T cells, a type of white blood cell that plays a key role in immune regulation, were also linked to better processing speed. This suggests that the balance between pro-inflammatory and anti-inflammatory activity in the immune system may be as important as the overall level of inflammation.
Strategies to support brain health
The research is observational, meaning it shows associations rather than direct cause-and-effect. However, it indicates that managing inflammation is important for cognitive function. Strategies that calm inflammation in the body may also support brain health.
Poor sleep is one of the fastest ways to increase inflammatory markers. Getting 7 to 9 hours of quality rest can help lower inflammation. Chronic stress keeps the immune system in a heightened state. Practices like meditation, breathwork, or regular walks can help manage stress.
Anti-inflammatory nutrition, including omega-3 fatty acids, colorful vegetables, and polyphenol-rich foods, while limiting ultra-processed options, may also be beneficial. Regular movement has well-documented anti-inflammatory effects. Consistent moderate exercise can help.
For those experiencing persistent cognitive symptoms after a viral infection, discussing inflammatory markers with a healthcare provider may be worthwhile.
