Elsevier established a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories. The article presents a systematic review and meta-analysis on fatigue and cognitive impairment in post-COVID-19 syndrome. It analyzed 81 studies, including 68 on fatigue and 43 on cognitive impairment. The results showed that 32% of individuals experienced fatigue and 22% had cognitive impairment 12 weeks or more after infection. Inflammatory markers were elevated in a subset of patients, and functional impairment was significant in some cases. The study found that females were more likely to report fatigue and cognitive impairment than males, and adults more than children. Objective assessments of fatigue and cognitive impairment showed higher prevalence than subjective ones. There was no significant difference in fatigue prevalence between hospitalized and non-hospitalized patients. Inflammatory parameters were elevated in 13 of 14 studies, with proinflammatory cytokines, CRP, D-dimer, and procalcitonin showing increases. Functional outcomes showed significant impairment in many patients, with 21% to 63% of individuals experiencing functional issues. Factors associated with post-COVID-19 syndrome included female sex, older age, severe acute illness, and pre-existing comorbidities. The study suggests that persistent inflammation may contribute to fatigue and cognitive impairment in post-COVID-19 syndrome. The study highlights the need for further research into the underlying mechanisms, standardized diagnostic criteria, and effective treatments for post-COVID-19 syndrome. It also notes limitations, including observational study design, potential selection bias, and the possibility that some symptoms may be related to chronic stress rather than infection.Elsevier established a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories. The article presents a systematic review and meta-analysis on fatigue and cognitive impairment in post-COVID-19 syndrome. It analyzed 81 studies, including 68 on fatigue and 43 on cognitive impairment. The results showed that 32% of individuals experienced fatigue and 22% had cognitive impairment 12 weeks or more after infection. Inflammatory markers were elevated in a subset of patients, and functional impairment was significant in some cases. The study found that females were more likely to report fatigue and cognitive impairment than males, and adults more than children. Objective assessments of fatigue and cognitive impairment showed higher prevalence than subjective ones. There was no significant difference in fatigue prevalence between hospitalized and non-hospitalized patients. Inflammatory parameters were elevated in 13 of 14 studies, with proinflammatory cytokines, CRP, D-dimer, and procalcitonin showing increases. Functional outcomes showed significant impairment in many patients, with 21% to 63% of individuals experiencing functional issues. Factors associated with post-COVID-19 syndrome included female sex, older age, severe acute illness, and pre-existing comorbidities. The study suggests that persistent inflammation may contribute to fatigue and cognitive impairment in post-COVID-19 syndrome. The study highlights the need for further research into the underlying mechanisms, standardized diagnostic criteria, and effective treatments for post-COVID-19 syndrome. It also notes limitations, including observational study design, potential selection bias, and the possibility that some symptoms may be related to chronic stress rather than infection.