Long COVID-19 effects on the olfactory, gustatory, and cognitive functions

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has had a profound and lasting impact on global public health. Beyond the acute phase of infection, many people develop Long COVID-19, a condition characterized by the persistence or appearance of new symptoms weeks or months after recovery. Among the most common and debilitating symptoms are olfactory and gustatory disorders, which significantly impair quality of life weeks or months after recovery.

This study aimed to investigate the frequency and characteristics of self-reported symptoms across three distinct phases—pre-infection, acute COVID-19, and post-acute (Long COVID-19)—focusing on chemosensory disturbances and cognitive abilities. To this end, an anonymous online questionnaire was administered, incorporating validated instruments and specific questions regarding participants’ clinical history. In addition, a subgroup of participants residing in Sardinia (Italy), specifically in the Cagliari area, underwent objective assessments of olfactory and gustatory functions using standardized tests integrating subjective reports with clinical experimental measures.

The results revealed a marked reduction in systemic symptoms from the acute to the post-acute phase; however, olfactory and gustatory impairments persisted in a substantial proportion of individuals, particularly among women and participants under 25 years of age. Our data show a significant correlation between chemosensory deficits and cognitive impairments. In conclusion, the results indicate that chemosensory dysfunction may serve as a potential clinical biomarker of Long COVID-19 and highlight the need for longitudinal studies to clarify the underlying pathophysiological mechanisms and guide the development of targeted therapeutic interventions.