These findings provide new insights into the early months of the pandemic and will help to inform the ongoing response, such as vaccination strategies.
Using data from over 5.5 million individuals, representing around 80% of the population of Catalonia, the study identified 102,002 patients who had an outpatient diagnosis of COVID-19, 16,901 who were hospitalised with COVID-19, and 5,273 who died after either being diagnosed or hospitalised with COVID-19 between 1st March and 6th May 2020.
On examining the characteristics of those with COVID-19, older age was the factor most strongly associated with worse outcomes (hospitalisations and deaths). Of the COVID-19 deaths observed, more than 80% were among individuals aged 70 or older. While COVID-19 deaths were concentrated among those at oldest ages, hospitalisations were less so. In fact, close to 40% of those hospitalised after an outpatient diagnosis of COVID-19 were aged between 40 and 59. Males were also seen to be at an increased risk of worse outcomes, making up 60% of deaths. Comorbidities were also associated with worse outcomes, although after adjusting for age and sex their impact were generally most pronounced among younger patients.
“This study has allowed us to better understand patient trajectories for COVID-19 during the first wave of the pandemic using linked primary care, hospital, COVID-19 testing, and death data from Catalonia” says lead author Edward Burn, a postdoctoral researched at the Fundació Institut Universitari per a la recerca a l'Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol), Barcelona, Spain, and the Centre for Statistics in Medicine (CSM), University of Oxford, UK.
“Understanding the differential risks of hospitalisation and mortality for different population strata is essential to plan shielding and vaccination strategies. Essentially, it is those more vulnerable to admission and death that we need to protect first to keep the impact of this pandemic under control” says Professor Dani Prieto-Alhambra, from the University of Oxford.
“This work shows how primary care records can provide an important foundation for COVID-19 research, particularly when linkage to testing, hospitalisation, and mortality data is available as it is in the SIDIAP database in Catalonia. Access to more up-to-date information together with the collaboration with other databases around the world will help us answering other key questions needed in the fight against this pandemic” says Talita Duarte-Salles, the principal investigator of the project at IDIAPJGol, Barcelona, Spain.
This project was funded by the Health Department from the Generalitat de Catalunya with a grant for research projects on SARS-CoV-2 and COVID-19 disease organized by the Direcció General de Recerca i Innovació en Salut. This project has received support from the European Health Data and Evidence Network (EHDEN) project. EHDEN received funding from the Innovative Medicines Initiative 2 Joint Undertaking (JU) under grant agreement No 806968. The JU receives support from the European Union's Horizon 2020 research and innovation programme and EFPIA.