Exploring predictors of post-COVID-19 condition among 810 851 individuals in Sweden, 2025, Xu et al.

[SNT Gatchaman]

Exploring predictors of post-COVID-19 condition among 810 851 individuals in Sweden

Spoiler: Authors

Xu, Yiyi; Li, Huiqi; Sigström, Robert; Lundberg-Morris, Lisa; Gisslén, Magnus; Larsson, Simon B; Nyberg, Fredrik; Bygdell, Maria

BACKGROUND
Long-term effects of COVID-19 can place burden on individuals, healthcare, and society. We aimed to evaluate the importance of a wide range of potential risk factors for being diagnosed with post-COVID-19 condition (PCC).

METHODS
We used data from national and regional registers and databases for all adult residents in the two largest regions in Sweden. Individuals with a first COVID-19 between 1 August 2020 and 9 February 2022 were included and followed until PCC diagnosis, censoring (death or migration), or 30 November 2023. Using Cox proportional hazards models and backwards stepwise selection, we evaluated a large set of risk factors including sociodemographic data, comorbidities, healthcare contact behaviors, COVID-19-related factors, as well as PCC in family and cohabitants (as proxies for genetics and shared environment).

RESULTS
We include 810,851 individuals (age range 18-106 years and 53.3% women), of whom 1.4% are diagnosed with PCC during follow-up. Female sex, older age, being born outside Sweden, higher educational attainment, essential workers, having comorbidities such as thromboembolic disease, asthma, fibromyalgia, depression/anxiety, and stress-related disorders, being infected earlier in the study period, experiencing severe acute COVID-19, not being vaccinated before COVID-19, and having a relative or a cohabitant with PCC are associated with an increased risk of being diagnosed with PCC.

CONCLUSIONS
In this large population-based cohort study, our exploratory analysis reveals several risk factors for being diagnosed with PCC. Our findings can serve as a basis for future targeting of preventive measures against PCC.

PLAIN LANGUAGE SUMMARY
Long-term effects of COVID-19 can place burden on individuals, healthcare, and society. We aimed to explore a wide range of potential risk factors for being diagnosed with post-COVID-19 condition (PCC). We included 810,851 individuals, of whom 1.4% were diagnosed with PCC during follow-up, using data from registers in Sweden. Female sex, older age, being born outside Sweden, higher educational attainment, essential workers, having comorbidities such as thromboembolic disease, asthma, fibromyalgia, depression/anxiety, and stress-related disorders, being infected earlier in the study period, experiencing severe acute COVID-19, not being vaccinated before COVID-19, and having a relative or a cohabitant with PCC are associated with an increased risk of being diagnosed with PCC. Our findings can serve as a basis for future targeting of preventive measures against PCC.

Web | PDF | Nature Communications Medicine | Open Access

 

[rvallee]

I don't know if this is unique or particular to medicine, but it's absolutely baffling how so many studies have been done, though almost all of them poor to the point of being useless, and absolutely nothing useful has been learned out of it. Not One thing. When we look back at the very first study done by a community of LC patients, everything that we know today was already known.

And yet nothing ever changes about... anything. Things just plow through, nothing is ever achieved or learned, the problem actually grows and yet almost no one is able to do anything because if anything, we might know less today than 50 years simply because of all the mass of garbage that has polluted the whole thing.

So much data. Very little useful information. No actual knowledge gained. Even though they started with way more than is needed. It's right there, and they can't even pluck the stuff that keeps falling on their lap. It's like a giant bystander effect, where most of the bystanders are literally the only people who can do something, but they all just stand around not getting anything, never actually doing anything worth doing, but utterly incapable of changing a damn thing about it.

Our findings can serve as a basis for future targeting of preventive measures against PCC.

Oh, sure, why the hell not? It will be delivered by either Santa or Satan during the week of four Thursdays, whoever is free and doesn't have water waiting to boil, I guess.

 

[SNT Gatchaman]

Using a large and rich population-based dataset with a source population covering approximately 40% of the Swedish population, we have a unique opportunity to address several remaining questions regarding risk factors for PCC. The aim of the present study was therefore to perform an explorative risk factor analysis covering a wide range of factors for the risk of receiving a diagnosis of PCC after the first SARS-CoV-2 infection in the total population.

A valid clinical diagnosis for PCC was defined as ICD-10-SE code U09.9 in NPR, VEGA, or VAL as the main or secondary diagnosis ≥28 days after index date. A minimum of 28 days between index date and PCC diagnosis was required, as a PCC diagnosis within 28 days was interpreted as a likely misclassification relating to health effects of the acute infection rather than PCC. In the sensitivity analysis, we used a 90-day interval between index date and a valid PCC diagnosis.

From the source population, 810 851 individuals had registered COVID-19 during the study inclusion period. Among these, 11 464 (1.4%) received a PCC diagnosis during follow-up. The time gap between the first infection and later PCC diagnosis ranged from one to 38 months with a median of 2.7 months. The majority (75%) of PCC cases got their diagnosis within 7 months after their first registered infection.

 

[SNT Gatchaman]

Regarding comorbidities, we show that preexisting thromboembolic disease, asthma, fibromyalgia, and common mental disorders (depression, anxiety, stress-related disorders) were associated with an increased risk of receiving a diagnosis of PCC in the multivariable model, and that preexisting stroke, dementia, and serious mental disorders (bipolar disorder, schizophrenia) were associated with a decreased risk.

In our study, individuals with serious mental disorders had a lower risk of PCC which could be due to an inherently lower risk of the condition for example related to genetic or environmental factors underlying these comorbidities that are also associated with a decreased risk for PCC. PCC could also be underdiagnosed in these patients due to for example overlapping symptoms, lower recognition of symptoms, or lower access to healthcare.In contrast, individuals with common mental disorders had a higher risk of PCC, perhaps because they are more vulnerable to certain PCC symptoms, or because these patients encounter healthcare more often and are more likely to have PCC detected.

Higher education attainment as well as being a healthcare worker were both associated with an increased risk of PCC in the analysis, while unemployment was associated with a reduced risk. […] It is quite rare that longer education is a risk factor for disease and unemployment protective. One explanation might be that it is easier for individuals with longer education to get a diagnosis of PCC than individuals with shorter education. For example, they may be more likely to be aware of PCC and its symptoms, have easier access to care, or have lower barrier to seek healthcare, possibilities that could also explain the higher risk for healthcare workers. Individuals with shorter education or without employment might seek care more seldom, or their symptoms might be overlooked, or attributed to other conditions.

We also observed that PCC in the core family or in cohabitants were risk factors for getting a diagnosis of PCC. […] PCC in the core family or in cohabitants could be seen as proxies for genetic and shared environmental factors meaning that these factors might influence the risk for PCC. This could indicate that the etiology of PCC involves genetic susceptibility, or that family and cohabitants’ experience of PCC increases awareness of long-term symptoms, which could facilitate navigation of the healthcare system.