Effect of Long COVID-19: Self-Reported Questionnaires and Objective Olfactory and Gustatory Evaluations

Background/Objectives: COVID-19 has triggered a global health crisis with sequelae ex-tending beyond the acute phase of infection. Long COVID-19 is characterized by the per-sistence or new onset of symptoms weeks to months after the initial infection, including fatigue, cognitive impairment, and chemosensory dysfunction. Despite growing clinical evidence, the underlying pathophysiological mechanisms remain incompletely under-stood. This study aimed to evaluate the prevalence, distribution, and evolution of symp-toms during the post-acute phases, with particular emphasis on olfactory and gustatory alterations. Methods: An observational study used a structured online questionnaire to collect demographic and clinical data from individuals with prior SARS-CoV-2 infection. Participants (n = 798) with persistent symptoms beyond 4–8 weeks were included. A sub-group of participants living in Sardinia underwent objective chemosensory assessment using the Sniffin’ Sticks test and the Taste Strips test for olfactory and gustatory function, respectively. Results: A high percentage of participants reported persistent symptoms con-sistent with long COVID-19, including fatigue, dyspnea, cognitive impairment, and chemosensory alterations. Olfactory and gustatory dysfunctions were among the most frequent manifestations. Objective assessments confirmed the presence and severity of these deficits, in accordance with data obtained using self-reported questionnaires. Symp-tom profiles evolved, suggesting possible central nervous system involvement and persis-tent inflammatory mechanisms. Conclusions: Long COVID-19 is a complex multisystem condition with a significant impact on quality of life. Chemosensory dysfunctions may serve as useful clinical markers for patient monitoring and stratification. Integrating sub-jective and objective data improves diagnostic accuracy and supports the development of targeted therapeutic strategies.