The aim of this study was to examine the associations between PASC and physical inactivity in a cohort of COVID-19 survivors (most of them admitted at ICU with pre-existing comorbidities) 6 to 11 months following hospitalization. The main findings are severalfold: i) The frequency of physical inactivity was substantive among patients with PASC (61%); ii) PASC was associated with 56% greater odds of physical inactivity; iii) the presence of ≥ 5 persistent symptoms vs. none increased the odds of physical inactivity by 133%; iv). Namely, dyspnea (122%), fatigue (96%), insomnia (59%), post-traumatic stress (53%), and severe muscle/joint pain (49%) were associated with greater odds of physical inactivity. This study provides novel data suggesting that PASC is associated with physical inactivity, which itself may be considered an expected persistent feature among COVID-19 survivors.
There is a growing body of knowledge calling the attention to a high prevalence of PASC worldwide2,4−6. Indeed, a significant proportion of COVID-19 survivors may still present with physical, mental, or cognitive symptoms 6 to 12 months after the acute infection, particularly in those following ICU treatment4,12−16. Whether PASC are risk factors predisposing to a physically inactive lifestyle was so far unexplored.
In our cohort of patients followed 6 to 11 months after hospitalization in a tertiary hospital, roughly 61% were physically inactive, which exceeds inactivity estimates of 47% for individuals of similar age observed in a population-based study in Brazil17. Interestingly, adjusted models suggested that PASC may predispose to physical inactivity, particularly when multiple symptoms are present. We were also able to identify specific symptoms predicting physical inactivity: severe muscle/joint pain, fatigue, post-traumatic stress, insomnia, and dyspnea. Even though the design of this study does not allow causative inferences, plausibility does exist to conjecture that these symptoms, especially when combined, may prevent one from achieving the recommended levels of physical activity.
To the best of our knowledge, this study is the first to investigate associations between individual PASC symptoms with physical inactivity. The adjusted regression models showed that not all PASC symptoms were associated with physical inactivity. The significant associations between specific PASC symptoms (i.e. fatigue, pain, dyspnea, and insomnia) and reduced physical activity could be mediated by different COVID-related pathologies, including persistent pulmonary18, renal19 or cardiovascular20 dysfunction. A proportion of PASC cases may also exhibit a form of myalgic encephalomyelitis/chronic fatigue syndrome 21, which is directly associated with signs of persistent systemic inflammation22 and can potentially lead to hypoactivity. Regarding mental symptoms, the finding that post-traumatic stress was more related to physical inactivity than depression or anxiety is also potentially interesting, indicating that there may be specific psychiatric manifestations that predispose to physical inactivity in PASC.
Independently of the pathophysiological bases underlying the presence of physical inactivity in association with PASC, an inactive lifestyle is a risk factor that has the potential to increase the demand on health systems worldwide, through increasing both the incidence and aggravation of chronic conditions10. Moreover, physical inactivity is an independent risk factor strongly associated with increased mortality; estimates using population attributed fractions suggested that physical inactivity can be responsible for 9% of all-cause mortality worldwide23. If COVID-19, and notably PASC, can result in sustained physical inactivity, patients’ survival may be also impacted. Given the multiple types of organ system dysfunctions that may contribute to PASC, further studies are warranted to investigate which of those pathologies may most significantly impact on the emergence of PASC-related physical inactivity – an emerging risk factor that may lead to higher rates of morbidity and mortality. Of relevance, the reversal of inactivity has the potential to attenuate physical, mental and cognitive symptoms that encompass PASC. Therefore, early identification of individuals that could benefit from interventions specifically tailored to promote physical activity may be key to mitigate, at least partially, the burden associated with PASC. Further studies are also warranted to investigate the accurate prevalence and prognostic value of physical inactivity among COVID-19 survivors, and the potential role of vaccination (and perhaps other therapies) on the prevention of inactivity, as seen with other PASC symptoms23.
This study is not free of limitations. The observational cross-sectional design hampers establishing cause-and-effect relationships as previously noted, and it may lead to reverse causation bias (i.e., physically inactive individuals may also be prone to PASC, such as fatigue, muscle/joint pain, dyspnea etc.). Also, we cannot rule out a potential selection bias (collider), since the present sample could differ from the population of those not selected or those who were unable/unwilling to participate. Physical activity levels were assessed through a questionnaire, and reflect the week prior to follow-up assessments. Moreover, the use of questionnaire to assess physical activity is prone to recall bias and overreporting.
In conclusion, among a cohort of COVID-19 survivors showing a high frequency of PASC 6 to 11 months following hospitalization, the number and type of PASC was predictive of physical inactivity. The novel data provided by this study warrant further investigations to ascertain which COVID-related organ system pathologies may most significantly contribute to the emergence of physical inactivity and help in the early identification of recovering COVID-19 patients who might benefit from interventions to combat inactivity. Considering the potential impact of this risk factor on overall morbidity and mortality and, hence, health systems, healthcare professionals and policy makers should be concerned about COVID-related physical inactivity.