Overall, the results show that patients three months after mild and moderate COVID-19 show at least one symptom in 61,9% of cases. As these symptoms are addressed as related to the SARS-CoV-2 infection they can be addressed as Long-COVID (11, 19–21). This percentage is similar to findings by Jacobsen et al. (22) but clearly lower as been reported by Huang et al. (9). The reason for this difference may be that Huang et al. had a higher number of severe and critical cases in their sample. Patients with longer artificial respiration periods and Intensive care treatment may develop SARS-CoV-2 independent symptoms, as described as Post-Intensive Care-Syndrome (PICS) (23).
The symptom profile from our study demonstrates that – besides effects symptoms related to pneumonia – non-specific symptom are dominating such as fatigue, mental symptoms and pain. Additionally a number of symptoms may be related to alterations of the nervous system. This is congruent with findings from Wang et al. (24) and Lenzen-Schulte (21). This profile shows similarities with the long-term symptoms of other severe diseases like cancer or auto-immune syndromes (25). One explanation for these similarities may be that in COVID-19 after the primary lung infection as second phase of the disease has been observed. This symptoms of the phase can be explained by a hyper-immune response (26). However the mechanisms of Long-COVID need to be elucidated further.
Date on the impact of Long-COVID on functioning are scarce. An Italian study described that about half of the Post-COVID-19 patients had severe impairments in physical functioning and activities of daily living at hospital discharge (27). Jacobson et al. (22) showed that 46% of the mildly affected patients and 73% of the hospitalized patients had an activity impairment due to the disease 3-4 months after their initial COVID-19 diagnosis. This is consistent with our findings that 49% of respondents reported at least one limitation of activities and/or restrictions in participation.
However, the mean levels of quality of life domains seems to be relatively close to the normal population. This shows that mild and moderate courses of the SARS-CoV-2 infection causes much less long-term alterations as compared with severe and critical causes as well as other SARS diseases (9). Nevertheless, the relatively young population of our survey show some conspicuous results. At the level of scales, SF-36 showed deficits of physical role, and slightly stronger in the scales of social function and emotional role . This may be related to findings that mental disorders are frequently seen in patients after SARS-CoV-2 infection (11, 28). The effects described are not as significant when the 18-64 age group is considered separately. However, the strongest deviations compared to the normal population also exist in the scales emotional role and social function. The long-term impact on activity and participation concerns only the minority of participants ranging from around 3 to 24 percent. The profile of alterations seems to relate to the above mentioned non-specific symptoms and mental problem and handling stress (24%) and managing daily demands (18%) are dominating. Another result has not been reported yet are problems with intimate relationships (12%).
The need for rehabilitation was not explicitly in the focus of the used questionnaire. However, the observed symptoms, activity limitations and participation restrictions suggest that a relevant need for rehabilitation is existent in the population of mild and severe SARS-CoV-2 infections. With regard to the symptom level the percentages of persons who need rehabilitation intervention can be estimated to 15-35%. The detected impact on functioning results in a relatively lower percentage in need for rehabilitation (estimated around 10-25%). Unfitness to work also occurs in the population of the survey, however their percentage is relatively low (around 5%). This can be seen as a sign that the people after mild and moderate COVID-19 may compensate the remaining problems relatively good. From the point of view of work performance the percentage of people in need of rehabilitation may only be around 5%.
The main limitation of the study is that it has been performed without a control group with matched samples. Due to the urgency and organizational problem it was not possible to recruit an appropriate control group. Another limitation is that we could not differentiate severity of the SARS-COV-2 infection because we had to use an anonymous data sampling approach. Also no detailed information about the possible phenomenon of presentism at the work place. It also can be discussed if a more sensitive questionnaire of life questionnaire could have made it possible to derive more differentiated profiles.
In conclusion, this retrospective questionnaire-bases survey show that patients with mild and moderate SARS-CoV-2 infection in the early phase of the disease the most frequent symptoms were fatigue, respiratory problems, limitations of the sense of taste and smell, fears and anxiety together with a broad range of other symptoms. In this phase, 84% of participants reported limitations of activity and participation, consisting mostly of carrying out daily routine, handling stress, doing household taking care for or support others as well as problems with leisure activities. At the time of survey that was around 3 months after the acute infection, 61.9% of participants reported at least one remaining symptoms such as fatigue, sleep disturbances, respiratory problems, pain, fears and anxiety and movement restrictions. Around 1/2 of the patients (49%) reported at least one activity limitations and participation restrictions such as handling stress, carrying out daily routine, looking after own health, relaxing and leisure activities carrying out house work.
Despite of these high numbers of symptoms and activity and participation the overall quality of life, as analyzed with the SF-36 Health Survey questionnaire sowed relatively small reduction of mean values as compared to the German normal sample. This is also the case in the population in working age. Only a small group of patients with mild and moderate COVID-19 experiences long-term unfitness for work.
These results show that long-term symptoms after mild and moderate COVID-19 are common and lead to limitations of activities and participation. However, it seem that in most cases they are not very severe and do not lead to frequent or severe issues with quality of live or work ability.