Fact check: What were the most common comorbidities among COVID-19 fatalities in the United States during the 2020 pandemic?

1. Competing studies tell a consistent story about which conditions mattered most

Multiple analyses from mid-2020 through early 2021 converge on a consistent list of comorbidities linked to COVID-19 deaths: cardiovascular disease, diabetes, chronic kidney disease, and chronic lung disease (including chronic pulmonary disease and COPD). The CDC’s analysis of decedents through May 18, 2020 reported these conditions as the most common, with 76.4% of decedents having at least one underlying condition ^[1]. Independent EHR-based research of tens of thousands of patients found similar patterns and additionally identified heart failure, myocardial infarction, dementia, liver and renal disease as predictors of higher odds of mortality ^{[2] [4] [5]}. Agreement across methods strengthens confidence that these conditions were the dominant comorbid contributors to mortality during 2020.

2. Why ranking differs — labels, data sources, and timing matter

Differences in which comorbidity is labeled “most common” reflect differences in dataset composition, diagnostic coding, and what investigators count as an underlying condition. The CDC report tallied underlying medical conditions on death records and surveillance forms, emphasizing cardiovascular disease and diabetes ^[1]. Federated EHR studies captured outpatient and inpatient diagnosis codes and sometimes reported chronic pulmonary disease and diabetes as the most frequent individual comorbidities ^[2]. A hospitalization-focused CDC publication that extended into 2021 emphasized hypertension, lipid disorders, and obesity as frequent among hospitalized adults, reflecting a cohort with different severity profiles ^[3]. Methodological differences explain apparent discrepancies more than substantive disagreement.

3. How common were these conditions in decedents — headline numbers

The CDC’s mid‑2020 analysis found that 60.9% of decedents had cardiovascular disease, 39.5% had diabetes mellitus, 20.8% had chronic kidney disease, and 19.2% had chronic lung disease, and overall 76.4% had at least one underlying medical condition ^[1]. EHR studies of tens of thousands of patients reported chronic pulmonary disease and diabetes prevalence in the mid‑teens among their cohorts (for example, 17.5% and 15.0% respectively in one large federated analysis), while other hospitalization-based datasets showed higher frequencies for hypertension and obesity ^{[2] [3]}. Absolute percentages vary by cohort, but cardiovascular disease and diabetes consistently appear near the top.

4. Which conditions most strongly predicted death, beyond simple frequency

Beyond prevalence, several studies assessed which comorbidities raised the odds of mortality. Federated EHR analysis and PLOS Medicine reporting identified myocardial infarction, congestive heart failure, dementia, chronic pulmonary disease, liver disease, renal disease, and metastatic cancer as associated with higher adjusted odds of death ^{[4] [5]}. These findings indicate that some less-common but more severe conditions conferred larger relative risks even if they were not the most common diagnoses listed on death certificates. Recognition of both prevalence and adjusted risk is important for clinical triage and public-health prioritization.

5. Demographics and social patterns changed the picture

Age, sex, and race/ethnicity modified how comorbidities related to fatal outcomes. Older age and male sex were consistently associated with higher mortality, while Black or African American race showed higher adjusted odds of death in several analyses ^{[2] [5]}. The CDC also reported that Hispanic and nonwhite decedents were younger on average than white decedents, indicating intersections between comorbidity burden, socio-demographic factors, and mortality timing ^[6]. Structural and access disparities likely contributed to the observed patterns, though the datasets differ in how thoroughly they capture social determinants.

6. Important caveats and data gaps that change interpretation

All sources have limitations: death certificate and surveillance reports can undercount or misclassify comorbidities, while EHRs reflect who sought care and which diagnoses were coded ^{[1] [2]}. Temporal changes in testing, hospitalization thresholds, and coding practices across 2020 mean apparent prevalence can shift over time; later hospitalization data (through March 2021) emphasize obesity and lipid disorders more than early death‑certificate series did ^[3]. Dementia and metastatic cancer increase adjusted mortality risk yet may be underrepresented on cause listings. These methodological constraints mean estimates should be read as complementary, not identical.

7. What to take away: a concise bottom line

During 2020 in the United States, cardiovascular disease and diabetes stood out as the most consistently common comorbidities among COVID-19 fatalities, with chronic kidney and chronic lung diseases also prominent; obesity, hypertension, and lipid disorders were frequent among hospitalized cohorts ^{[1] [3]}. Multiple large‑scale analyses support this core conclusion, while differences in ranking reflect datasets, coding, and timing rather than fundamental contradictions. Policy and clinical decisions should consider both how common a condition was and how much it increased the risk of death.