TL;DR
A social media analysis presented at the NEI Fall Congress found that people discussing narcolepsy and idiopathic hypersomnia often described brain fog through memory and concentration problems, not just tiredness. The findings come from self-selected online communities and cannot establish how common these experiences are among all patients.
A social media analysis of 554,312 posts and comments from online communities for people with narcolepsy and idiopathic hypersomnia found that users commonly described brain fog as a problem with memory and concentration, rather than simply fatigue. The findings, presented by Anne Marie Morse, DO, and colleagues at the Neuroscience Education Institute’s Fall Congress, suggest clinicians may need to ask about brain fog as a distinct symptom, though the study cannot show how prevalent it is among all patients.
The researchers examined posts from the r/Narcolepsy and r/idiopathichypersomnia subreddits and the Facebook group PWN4PWN, published between August 2011 and September 2025. About 85% of the material came from r/Narcolepsy. The team used semantic similarity analysis to identify words and experiences connected with “brain fog.”
Among the most closely associated terms were “tiredness,” “difficulty concentrating,” “inability to focus,” “poor memory” and “memory issues.” The leading descriptions of clinical experiences included impaired memory, impaired concentration, fatigue and forgetfulness. Other frequent contextual words included “drunkenness” and “dissociation.” Terms associated with relief included “clears,” “lifted,” “lifts” and “clearing.”
The authors also compared posts mentioning fatigue or sleepiness across four groups, based on which symptom was more prominent. People in the fatigue-and-sleepiness-balanced group more often linked brain fog to memory and focus. Those in the very sleepiness-dominant group more often connected it with energy and motivation, and used intensity or duration words such as “constant,” “intense” and “severe.” These patterns describe language in the sampled posts, not clinical measurements of symptoms.
Why Symptom Language Matters
The findings matter because patients and clinicians may use “brain fog” to mean different things. If the term is routinely treated as another way to say fatigue or sleepiness, memory and concentration problems may not be discussed directly. Morse said clinicians should ask patients to describe the experience in their own words and treat the response as a symptom in its own right.
That distinction could affect how researchers measure the burden of sleep disorders, too. Morse said a stable, shared vocabulary in patient communities may help researchers develop patient-reported measures that reflect how people describe their day-to-day difficulties. The analysis does not establish that such a measure has been created or validated; it points to a possible direction for further work.
Morse said patients describe cognitive difficulties as affecting school, work, driving and being present with family. Those examples are her characterization of what patients report, rather than outcomes quantified by this analysis. The study did not measure how often these activities were affected.
How the Online Analysis Was Built
Morse told MedPage Today that researchers wanted to learn how people with narcolepsy type 1, narcolepsy type 2 and idiopathic hypersomnia used “brain fog” without being prompted in a clinical or research setting. She said previous work by the group found the phrase predated COVID-19 by at least a decade, while its use later grew alongside research into symptoms across several conditions. The current analysis focused on how sleep-disorder communities described the term.
Posts mentioning brain fog increased annually from 2011 to 2017, then remained at approximately 1% of all posts through 2025, according to the report. The researchers found a shift in descriptors between 2011–2017 and 2018–2020, away from memory-focused language and toward exhaustion and tiredness. They reported that the meaning remained consistent from 2018 through 2025. These figures refer to the sampled online posts, not the share of patients experiencing brain fog.
“In the community data, [brain fog] separates out as its own concept, and its meaning has been stable since 2018.”
— Anne Marie Morse, DO, of Geisinger Medical Center, speaking to MedPage Today
Limits of the Community Sample
The findings cannot establish how often people with narcolepsy or idiopathic hypersomnia experience brain fog, or whether the language reflects patients outside the online groups. The researchers noted that online communities are self-selected and reflect conversational patterns rather than population prevalence. They also could not independently verify users’ clinical diagnoses from social media posts.
The analysis identifies associations between words and descriptions; it does not show that one symptom causes another, compare brain fog across diagnoses in a clinically representative sample, or test a treatment. The authors also did not establish a single agreed definition of brain fog. It remains unclear how well the observed vocabulary applies to patients who do not use these platforms.
From Patient Language to Measures
The report presents patient-generated language as a potential starting point for research into a patient-reported outcome measure, but further work would be needed to develop and validate such a tool. Studies involving broader and clinically verified groups could test whether the same descriptions hold across diagnoses and settings.
For now, Morse’s practical recommendation is to ask patients what they mean by brain fog and document their answer, rather than assuming it is equivalent to fatigue or sleepiness. The conference analysis does not report a new clinical guideline or treatment. Its next step is to see whether the language identified in online discussions can support better symptom measurement and clinical conversations.
Key Questions
What did the analysis find about brain fog?
In the sampled posts, people commonly associated brain fog with memory problems and difficulty concentrating. Fatigue and tiredness also appeared, but the researchers said the term was not simply interchangeable with either fatigue or sleepiness.
Which sleep disorders did the communities discuss?
The analysis focused on online communities for narcolepsy and idiopathic hypersomnia. The report said researchers aimed to understand language used by people with narcolepsy types 1 and 2 and idiopathic hypersomnia.
Does the study show how many patients have brain fog?
No. The 554,312 figure is the number of posts and comments analyzed, not the number of patients. Because the groups were self-selected and diagnoses could not be verified from posts, the analysis does not measure prevalence among all people with these disorders.
What did the researcher recommend clinicians do?
Morse recommended asking patients to explain brain fog in their own words and treating it as a distinct symptom to discuss, rather than automatically translating it into fatigue or sleepiness.
Source: medpagetoday.com
