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Background: Olfactory impairment has been associated with adverse health outcomes, particularly in older populations, including cognitive decline, malnutrition, and frailty. The COVID-19 pandemic highlighted olfactory impairment as a key symptom affecting individuals across all age groups, raising concerns about its long-term impacts. This study investigates the association between post-acute olfactory impairment and long-term physical capacity in COVID-19 patients, hypothesizing that impaired olfaction is linked to reduced physical performance.

Methods: This prospective cohort study included 63 hospitalized and non-hospitalized COVID-19 patients (38.1 % women; median age 51 years, IQR 47.0–60.0) who underwent olfactory testing 1–3 months post-infection. Olfactory assessments included threshold screening, supra-threshold intensity ratings, and an odour identification test. Physical capacity was assessed using the 1-min sit-to-stand test at follow-ups (3, 6, 12, and 24 months). Partial correlation analysis and linear mixed models were used to analyse the data, adjusting for covariates such as age, sex, BMI, comorbidities, smoking status, and severity of infection.

Results: In the early post-acute phase, 36.5 % of participants exhibited olfactory impairment. We identified a significant, negative correlation between objectively tested olfactory impairment and physical capacity at all follow-ups. In a linear mixed model adjusted for relevant covariates, olfactory impairment was associated with reduced physical capacity up to 24 months after infection. The association strengthened over time, reflected by the increasing beta values for the interaction term: 0.09 (p = 0.200) at 6 months, 0.13 (p = 0.053) at 12 months, and 0.23 (p = 0.001) at 24 months.

Conclusion: Individuals with olfactory impairment in the early post-acute phase of COVID-19 infection were more likely to exhibit diminished physical capacity 24 months later. This study highlights the broader implications of olfactory impairment, previously noted mainly in older populations, demonstrating its relevance across age groups. The COVID-19 pandemic presented a unique opportunity to investigate this relationship, enhancing our understanding of how olfactory impairments relate to long-term physical performance. These findings emphasize the need for further research with larger, more diverse cohorts and objective longitudinal assessments to confirm and extend these observations.

Background: Olfactory dysfunction together with neurological and cognitive symptoms are common after COVID-19. We aimed to study whether performance on olfactory and neuropsychological tests following infection predict post-COVID condition (PCC), persisting symptoms, and reduced health-related quality of life.

Methods: Both hospitalized (N = 10) and non-hospitalized individuals (N = 56) were enrolled in this prospective cohort study. Participants were evaluated 1–3 months after infection with an olfactory threshold test and neuropsychological tests, which was used as predictors of PCC. A questionnaire outlining persisting symptoms and the validated instrument EuroQol five-dimension five-level for health-related quality of life assessment were used as outcome data 1 year after infection (N = 59). Principal component analysis was used to identify relevant predictors for PCC at 1 year.

Results: Objectively assessed olfactory dysfunction at 1–3 months post infection, but not subjective olfactory symptoms, predicted post-COVID condition with reduced health-related quality of life (PCC+) at 1 year. The PCC+ group scored more often below the cut off for mild cognitive impairment on the Montreal Cognitive Assessment (61.5% vs. 21.7%) and higher on the Multidimensional Fatigue Inventory-20, compared to the group without PCC+.

Conclusion: Our results indicate that objectively assessed, olfactory dysfunction is a predictor for PCC+. These findings underscore the importance of objective olfactory testing. We propose that olfactory screening in the early post-acute phase of COVID-19 infection might identify individuals that are at higher risk of developing long-term health sequalae.

Background: The long-term sequelae after COVID-19 constitute a challenge to public health and increased knowledge is needed. We investigated the prevalence of self-reported persistent symptoms and reduced health-related quality of life (HRQoL) in relation to functional exercise capacity, 6 months after infection, and explored risk factors for COVID-19 sequalae.

Methods: This was a prospective, multicenter, cohort study including 434 patients. At 6 months, physical exercise capacity was assessed by a 1-minute sit-to-stand test (1MSTST) and persistent symptoms were reported and HRQoL was evaluated through the EuroQol 5-level 5-dimension (EQ-5D-5L) questionnaire. Patients with both persistent symptoms and reduced HRQoL were classified into a new definition of post-acute COVID syndrome, PACS+. Risk factors for developing persistent symptoms, reduced HRQoL and PACS+ were identified by multivariable Poisson regression.

Results: Persistent symptoms were experienced by 79% of hospitalized, and 59% of non-hospitalized patients at 6 months. Hospitalized patients had a higher prevalence of self-assessed reduced overall health (28 vs. 12%) and PACS+ (31 vs. 11%). PACS+ was associated with reduced exercise capacity but not with abnormal pulse/desaturation during 1MSTST. Hospitalization was the most important independent risk factor for developing persistent symptoms, reduced overall health and PACS+.

Conclusion: Persistent symptoms and reduced HRQoL are common among COVID-19 survivors, but abnormal pulse and peripheral saturation during exercise could not distinguish patients with PACS+. Patients with severe infection requiring hospitalization were more likely to develop PACS+, hence these patients should be prioritized for clinical follow-up after COVID-19.