Factors associated with low anaerobic threshold and its impact on sleep quality and health-related quality of life in individuals with long COVID.

INTRODUCTION

Anaerobic threshold (AT), a crucial indicator of submaximal exercise capacity and cardiorespiratory function, has been reported to be impaired in individuals with long COVID. However, the predictors of reduced AT during exercise in this population and its impacts on patient-reported outcomes, including sleep quality and health-related quality of life (HRQL), remain unknown. This study aims to identify factors associated with low AT and examine its relationship with patient-reported outcomes.

OBJECTIVE

To investigate the predictors of low AT and compare patient-reported outcomes (sleep quality and HRQL) between individuals with normal and low AT among those with long COVID.

DESIGN

Cross-sectional study.

SETTING

Post-COVID integrated outpatient clinic at a medical center in northern Taiwan.

PATIENTS (OR PARTICIPANTS): Eligible patients aged 20-80 years with long COVID were recruited.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURE(S): AT, peak oxygen consumption (peak VO2), and patient-reported outcomes, including sleep quality and HRQL, assessed using the Taiwanese version of the World Health Organization Quality of Life-BREF and Pittsburgh Sleep Quality Index.

RESULTS

Factors associated with low AT included younger age (odds ratio [OR] = 0.904, 95% confidence interval [CI]: 0.867-0.942, p < .001) and lower peak VO2 (OR = 0.737, 95% CI: 0.659-0.842, p < .001). Participants with low AT exhibited impaired patient-reported outcomes including poorer sleep quality (p = .008), and lower HRQL scores across all domains, as compared to those with normal AT. After adjustment for significant covariates, only the psychological domain of HRQL remained statistically significant (adjusted p = .035).

CONCLUSIONS

Low AT in individuals with long COVID was associated with younger age and lower peak VO2. Its independent impact on sleep quality and HRQL appears limited, suggesting that patient-reported outcomes may be influenced by multiple interacting factors and warrant further investigation.