In this study, we investigated whether treatment with palmitoylethanolamide and luteolin (PEA-LUT) leads to improvement in the quantitative or qualitative measures of olfactory dysfunction or relief from mental clouding in patients affected by long COVID. Patients with long COVID olfactory dysfunction were allocated to different groups based on the presence ("previously treated") or absence ("naïve") of prior exposure to olfactory training. Patients were then randomized to receive PEA-LUT alone or in combination with olfactory training. Olfactory function and memory were assessed at monthly intervals using self-report measures and quantitative thresholds. A total of 69 patients (43 women, 26 men) with an age average of 40.6 + 10.5 were recruited. PEA-LUT therapy was associated with a significant improvement in validated odor identification scores at the baseline versus each subsequent month; assessment at 3 months showed an average improvement of 10.7 + 2.6, CI 95%: 6-14 (p < 0.0001). The overall prevalence of parosmia was 79.7% (55 patients), with a significant improvement from the baseline to 3 months (p < 0.0001), namely in 31 patients from the Naïve 1 group (72%), 15 from the Naïve 2 group (93.7%), and 9 from the remaining group (90%). Overall, mental clouding was detected in 37.7% (26 subjects) of the cases, with a reduction in severity from the baseline to three months (p = 0.02), namely in 15 patients from the Naïve 1 group (34.8%), 7 from the Naïve 2 group (43.7%), and 4 from the remaining group (40%). Conclusions. In patients with long COVID and chronic olfactory loss, a regimen including oral PEA-LUT and olfactory training ameliorated olfactory dysfunction and memory. Further investigations are necessary to discern biomarkers, mechanisms, and long-term outcomes.
Keywords: COVID-19; PEA-LUT; anosmia; brain fog; hyposmia; long-haul COVID syndrome; lutein; memory; mental clouding; neuroinflammation; olfactory threshold; olfactory training; palmitoylethanolamide; parosmia; post-acute sequelae of SARS-CoV-2 infection (PASC); qualitative smell disorders; smell disorders.