Risk factors for COVID-19 diagnosis, hospitalization, and subsequent all-cause mortality in Sweden: a nationwide study

Eur J Epidemiol. 2021 Mar;36(3):287-298. doi: 10.1007/s10654-021-00732-w. Epub 2021 Mar 11.


We conducted a nationwide, registry-based study to investigate the importance of 34 potential risk factors for coronavirus disease 2019 (COVID-19) diagnosis, hospitalization (with or without intensive care unit [ICU] admission), and subsequent all-cause mortality. The study population comprised all COVID-19 cases confirmed in Sweden by mid-September 2020 (68,575 non-hospitalized, 2494 ICU hospitalized, and 13,589 non-ICU hospitalized) and 434,081 randomly sampled general-population controls. Older age was the strongest risk factor for hospitalization, although the odds of ICU hospitalization decreased after 60-69 years and, after controlling for other risk factors, the odds of non-ICU hospitalization showed no trend after 40-49 years. Residence in a long-term care facility was associated with non-ICU hospitalization. Male sex and the presence of at least one investigated comorbidity or prescription medication were associated with both ICU and non-ICU hospitalization. Three comorbidities associated with both ICU and non-ICU hospitalization were asthma, hypertension, and Down syndrome. History of cancer was not associated with COVID-19 hospitalization, but cancer in the past year was associated with non-ICU hospitalization, after controlling for other risk factors. Cardiovascular disease was weakly associated with non-ICU hospitalization for COVID-19, but not with ICU hospitalization, after adjustment for other risk factors. Excess mortality was observed in both hospitalized and non-hospitalized COVID-19 cases. These results confirm that severe COVID-19 is related to age, sex, and comorbidity in general. The study provides new evidence that hypertension, asthma, Down syndrome, and residence in a long-term care facility are associated with severe COVID-19.

Keywords: COVID-19; Case–control study; Cohort study; Coronavirus; Epidemiology; SARS-CoV-2.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • COVID-19 / diagnosis*
  • COVID-19 / epidemiology*
  • COVID-19 / mortality
  • Comorbidity
  • Female
  • Hospitalization / statistics & numerical data*
  • Humans
  • Intensive Care Units / statistics & numerical data*
  • Male
  • Middle Aged
  • Mortality / trends*
  • Residential Facilities / statistics & numerical data
  • Risk Factors
  • SARS-CoV-2
  • Sex Factors
  • Socioeconomic Factors
  • Sweden / epidemiology
  • Young Adult