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The following is a summary of “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,” published in the September 2024 issue of Infectious Diseases by Moniz et al.

Determining symptom clusters in long COVID is essential for creating targeted treatments and enhancing the QoL for those affected by this condition.

Researchers conducted a retrospective study to determine and compare symptom clusters at 9 and 12 months after SARS-CoV-2 infection and to describe these clusters based on factors at the time of infection.

They selected individuals randomly from the Portuguese National System of Epidemiological Surveillance (SINAVE) database. Participants with positive SARS-CoV-2 were tested via RT-PCR in August 2022 and were contacted for a telephonic interview about 9 and 12 months later. A hierarchical clustering analysis was conducted using Euclidean length and Ward’s linkage; clustering was based on the 35 symptoms reported at 9 and 12 months after the positive SARS-CoV-2 test and was distinguished by age, sex, pre-existing health conditions, and symptoms present during the SARS-CoV-2 infection.

The results showed 552 individuals at 9 months and 458 at 12 months, with a median age of 52 years ( interquartile range (IQR): 40–64 years) and 59% being female. Hypertension and high cholesterol were common pre-existing health conditions. Memory loss, fatigue or weakness, and joint pain were often reported symptoms at 9 and 12 months post-positive test, while 4 clusters occurred at both time points: no or minor symptoms, multi-symptoms, joint pain, and neurocognitive-related symptoms. Clusters remained constant, while memory loss and concentration issues were high in frequency within the neurocognitive cluster at 12 months. The multi-symptoms cluster had older individuals, more females, and pre-existing health conditions at 9 months, while at 12 months, older individuals and those with more pre-existing health conditions were more dominant in the joint pain cluster.

They concluded that COVID is a heterogeneous condition with distinct symptom clusters that remain relatively stable over time, suggesting the validation and analysis of risk factors to develop targeted treatments.

Source: bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-024-09896-8