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. 2024 Sep 19;24(1):1001.
doi: 10.1186/s12879-024-09896-8.

Long COVID is not the same for everyone: a hierarchical cluster analysis of Long COVID symptoms 9 and 12 months after SARS-CoV-2 test

Marta Moniz  1 , Carolina Ruivinho  2 , Ana Rita Goes  2 , Patrícia Soares  2   3 , Andreia Leite  2   3
Affiliations

Long COVID is not the same for everyone: a hierarchical cluster analysis of Long COVID symptoms 9 and 12 months after SARS-CoV-2 test

Marta Moniz et al. BMC Infect Dis. .

Erratum in

Abstract

Background: Identifying symptom clusters in Long COVID is necessary for developing effective therapies for this diverse condition and improving the quality of life of those affected by this heterogeneous condition. In this study, we aimed to identify and compare symptom clusters at 9 and 12 months after a SARS-CoV-2 positive test and describe each cluster regarding factors at infection.

Methods: This is a cross-sectional study with individuals randomly selected from the Portuguese National System of Epidemiological Surveillance (SINAVE) database. Individuals who had a positive RT-PCR SARS-CoV-2 test in August 2022 were contacted to participate in a telephonic interview approximately 9 and 12 months after the test. A hierarchical clustering analysis was performed, using Euclidean distance and Ward's linkage. Clustering was performed in the 35 symptoms reported 9 and 12 months after the SARS-CoV-2 positive test and characterised considering age, sex, pre-existing health conditions and symptoms at time of SARS-CoV-2 infection.

Results: 552 individuals were included at 9 months and 458 at 12 months. The median age was 52 years (IQR: 40-64 years) and 59% were female. Hypertension and high cholesterol were the most frequently reported pre-existing health conditions. Memory loss, fatigue or weakness and joint pain were the most frequent symptoms reported 9 and 12 months after the positive test. Four clusters were identified at both times: no or minor symptoms; multi-symptoms; joint pain; and neurocognitive-related symptoms. Clusters remained similar in both times, but, within the neurocognitive cluster, memory loss and concentration issues increased in frequency at 12 months. Multi-symptoms cluster had older people, more females and more pre-existing health conditions at 9 months. However, at 12 months, older people and those with more pre-existing health conditions were in joint pain cluster.

Conclusions: Our results suggest that Long COVID is not the same for everyone. In our study, clusters remained similar at 9 and 12 months, except for a slight variation in the frequency of symptoms that composed each cluster. Understanding Long COVID clusters might help identify treatments for this condition. However, further validation of the observed clusters and analysis of its risk factors is needed.

Keywords: Long COVID; Portugal; Public health; Symptoms cluster.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Frequency of Long COVID symptoms 9 (A) and 12 (B) months after a SARS-CoV-2 positive test
Fig. 2
Fig. 2
Dendrogram based on hierarchical clustering analysis of 37 symptoms reported (A) 9 months after SARS-CoV-2 positive test, and (B) 12 months after SARS-CoV-2 positive test
Fig. 3
Fig. 3
Bubble plot of symptom cluster frequency derived from hierarchical clustering of Long COVID symptoms 9 months after a SARS-COV-2 positive test
Fig. 4
Fig. 4
Radar plots displaying the frequency of Long COVID symptoms across all four clusters. Abbreviations: LA: Loss of appetite; No feeling: Not feeling one side of the body or face; BD: Breathing difficulties
Fig. 5
Fig. 5
Bubble plot of symptom cluster frequency derived from hierarchical clustering of Long COVID symptoms 12 months after a SARS-COV-2 positive test
Fig. 6
Fig. 6
Radar plots displaying the frequency of Long COVID symptoms across all four clusters. Abbreviations: LA: Loss of appetite; No feeling: Not feeling one side of the body or face; BD: Breathing difficulties
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