Prevalence and long-term outcomes of brain fog and cognitive impairment in individuals with long COVID: A systematic review

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Moderate to high prevalence rates with consistent gender differences

• Primary Outcome: Pooled prevalence of brain fog: 30% (95% CI: 28-32%); cognitive impairment: 25% (95% CI: 23-27%)

• Nnt Or Sensitivity: Gender-specific prevalence: females 34% vs males 23% for brain fog; females 29% vs males 21% for cognitive impairment

• Confidence Interval: Narrow confidence intervals suggesting good precision

Clinical Application

High feasibility for screening and monitoring in Australian healthcare settings Relevant to RACGP long COVID guidelines and potential PBS-funded cognitive rehabilitation programs. Important for GP management and specialist referral pathways Adults with confirmed long COVID syndrome, particularly relevant for primary care and specialist follow-up

Abstract

BACKGROUND: Long COVID is increasingly recognized as a complex multisystem condition, with brain fog and cognitive impairment emerging as some of its manifestations. Despite growing literature, the pooled prevalence, subgroup differences, and underlying mechanisms remain incompletely understood. METHODS: We systematically reviewed 47 studies (2000-2025) encompassing over 25,000 patients to evaluate the prevalence of brain fog and cognitive impairment among long COVID populations. Data were extracted on study design, patient demographics, follow-up duration, and subgroup variables including gender, hospitalization, vaccination, and geographic region. Risk of bias was assessed using the Newcastle-Ottawa Scale (NOS v9.0) and JBI checklists. Quantitative synthesis was performed with subgroup and temporal analyses, presented in forest plots and summary figures. RESULTS: The pooled prevalence of brain fog was 30% (95% CI: 28-32), while cognitive impairment was 25% (95% CI: 23-27). Female patients consistently showed higher rates compared to males (34% vs 23% for brain fog; 29% vs 21% for cognitive impairment). Community-managed patients demonstrated higher prevalence compared to hospitalized cohorts, and unvaccinated individuals had a greater burden than vaccinated ones. Temporal analyses indicated that prevalence increased with longer follow-up, suggesting symptom persistence or late manifestation. Pathophysiological explanations include neuroinflammation, microvascular injury, immune dysregulation, and psychosocial stressors. CONCLUSION: Brain fog and cognitive impairment are common, persistent, and clinically significant features of long COVID. Gender differences, vaccination status, and follow-up duration influence prevalence. Future studies should focus on mechanisms, preventive strategies, and targeted interventions to mitigate long-term cognitive sequelae.

References

1. 1.Faseeh, A., Rida, M., Karim, N. E., Zafar, A., Shah, A., & Perveen, A. (2026). Prevalence and long-term outcomes of brain fog and cognitive impairment in individuals with long COVID: A systematic review. Medicine, Article 0000000000049022. https://doi.org/10.1097/MD.0000000000049022