4.2. Limitations of study
cognitive impairment
Despite the novel approach of our study, it is crucial to note some of its limitations. All participants were infected with the delta variant, which, in contrast to the omicron variant, exerted less neurotropism. Furthermore, sleep disturbances as a common comorbidity signif mild cognitive impairment, and therefore, proper cooperation in rehabilitation programs could be masked by such confounding factors, meaning that more studies are required to elucidate the causal interrelationship.