A Retrospective Analysis of Hyperlipidemia and COVID-19 Outcomes Investigated in a Rural Midwestern Population

Abstract

Background COVID-19 is a respiratory disease caused by SARS-CoV-2, a coronavirus discovered in 2019. Its impact on the world continues to be studied due to the significant death toll of the disease. As the COVID-19 pandemic remains ongoing, examining the association of COVID-19 with comorbidities and resulting mortality is necessary. This study focuses on population health outcomes with COVID-19 infection and hyperlipidemia (total cholesterol greater than or equal to 200 mg/dL) as a comorbidity, including potential associations with age and sex. Methods As a retrospective analytical study, patients were divided into three populations based on COVID-19 and/or hyperlipidemia based on the International Classification of Diseases, Tenth Edition (ICD-10) codes reported in the electronic medical record system at Freeman Health System (FHS) in Southwest Missouri from April 1, 2020, to December 31, 2021. Wald's methods and two sample proportion summary hypotheses with confidence intervals (CIs) were used for comparison. The populations were subdivided and analyzed for age and sex differences. Results Patients with both COVID-19 and hyperlipidemia had a higher mortality rate than patients with COVID-19 and without hyperlipidemia and patients with hyperlipidemia and without COVID-19; patients with COVID-19 and without hyperlipidemia had a higher mortality rate than patients with hyperlipidemia and without COVID-19. All comparisons across these populations were statistically significant (p-value < 0.05). While increased age was associated with increased mortality in all groups, sex was not predictive in this regard. Conclusion Our study provides insights into variables affecting COVID-19 outcomes in a rural Midwestern population by showing how the comorbidity hyperlipidemia contributes to increased mortality.

Keywords: cardiovascular disease; cholesterol; coronavirus; covid-19; hyperlipidemia; midwest; missouri; preventative care; rural; serum lipid levels.

Figure 1. Population Classification Flowchart Without COVID-19 Based on ICD-10 Codes

Using ICD-10 codes to collect patient information, the code U071 (COVID-19) was used to exclude those from the sample set. Patients without an ICD-10 code U071 were included and subdivided into expired and discharged populations. The population of patients without COVID-19 was refined based on exclusion criteria, eliminating duplicate patients and patients who did not have hyperlipidemia based on ICD-10 codes E782 (mixed hyperlipidemia), E7849 (other hyperlipidemia), and E785 (hyperlipidemia). These groups were subdivided into patients who expired and those who were discharged. ICD-10: International Classification of Diseases, Tenth Edition, COVID-19: coronavirus disease 2019

Figure 2. Population Classification Flowchart With COVID-19 Based on ICD-10 Codes

The ICD-10 code used to collect patient information was U071 (COVID-19). Populations were excluded based on duplicate admissions and then subdivided into patients who expired and patients who were discharged. The population of COVID-19 patients was subdivided again into those who did and did not have ICD-10 codes for hyperlipidemia as follows: E782 (mixed hyperlipidemia), E7849 (other hyperlipidemia), and E785 (hyperlipidemia). These groups were subdivided into patients who expired and those who were discharged. ICD-10: International Classification of Diseases, Tenth Edition, COVID-19: coronavirus disease 2019

Figure 3. Total Counts of Patient Populations With COVID-19 and Hyperlipidemia

Data was extracted from ICD-10 codes from FHS in Joplin and Neosho, Missouri. The population was classified into three groups: patients with both COVID-19 and hyperlipidemia (727 patients in total: 146 expired and 581 discharged) (Figure 1), patients with COVID-19 and without hyperlipidemia (1,002 patients) (Figure 1), and patients with hyperlipidemia and without COVID-19 (5,712 patients in total: 315 expired and 5,397 discharged) (Figure 2). Analysis of intervals was reported with 95% confidence. COVID-19: coronavirus disease 2019, ICD-10: International Classification of Diseases, Tenth Edition

Figure 4. Mortality Confidence Intervals in Individual Populations Based on COVID-19 and Hyperlipidemia

Wald’s methods were used for analysis. Populations with and without COVID-19 and/or hyperlipidemia were assessed. Patients with both COVID-19 and hyperlipidemia had a mortality rate between 17.17% and 22.99%. Patients with COVID-19 and without hyperlipidemia had a mortality rate between 13.51% and 18.03%. Patients with hyperlipidemia and without COVID-19 had a mortality rate between 4.92% and 6.11%. COVID-19: coronavirus disease 2019

Figure 5. Mortality Confidence Intervals in Two Sample Comparisons Based on COVID-19 and Hyperlipidemia

The population of patients with both COVID-19 and hyperlipidemia had a statistically significant mortality rate between 0.63% and 8.00% higher than patients with COVID-19 and without hyperlipidemia (p-value = 0.02). The population of patients with both COVID-19 and hyperlipidemia had a statistically significant mortality rate between 11.60% and 17.54% higher than patients with hyperlipidemia and without COVID-19 (p-value < 0.0001). The population of patients with COVID-19 and without hyperlipidemia had a statistically significant mortality rate between 7.92% and 12.59% higher than the patients with hyperlipidemia and without COVID-19 (p-value < 0.0001). Two sample proportion summary hypotheses with CI were calculated for the proportion difference between populations. CI: confidence interval, COVID-19: coronavirus disease 2019

Figure 6. Mortality Confidence Intervals by Individual Populations Divided by Age, Sex, COVID-19, and Hyperlipidemia

Using the populations defined in Table 1, raw data in Table 4, and Wald’s methods for analysis, P1 represents patients who were male with both COVID-19 and hyperlipidemia, with a mortality rate between 18.26% and 26.29%; P2 represents patients who were female with both COVID-19 and hyperlipidemia, with a mortality rate between 13.02% and 21.37%; P3 represents patients who were greater or equal to 65 years old with both COVID-19 and hyperlipidemia, with a mortality rate between 18.78% and 26.38%; P4 represents patients who were less than 65 years old with both COVID-19 and hyperlipidemia, with a mortality rate between 11.25% and 20.05%; P5 represents patients who were male with COVID-19 and without hyperlipidemia, with a mortality rate between 13.31% and 19.59%; P6 represents patients who were female with COVID-19 and without hyperlipidemia, with a mortality rate between 11.75% and 18.23%; P7 represents patients who were greater or equal to 65 years old with COVID-19 and without hyperlipidemia, with a mortality rate between 17.70% and 25.84%; P8 represents patients who were less than 65 years old with COVID-19 and without hyperlipidemia, with a mortality rate between 9.29% and 14.43%; P9 represents patients who were male with hyperlipidemia and without COVID-19, with a mortality rate between 4.82% and 6.48%; P10 represents patients who were female with hyperlipidemia and without COVID-19, with a mortality rate between 4.53% and 6.22%; P11 represents patients who were greater or equal to 65 years old with hyperlipidemia and without COVID-19, with a mortality rate between 5.79% and 7.39%; and P12 represents patients who were less than 65 years old with hyperlipidemia and without COVID-19, with a mortality rate between 2.75% and 4.37%. CI: confidence interval, COVID-19: coronavirus disease 2019

Figure 7. Mortality Confidence Intervals in Two Sample Comparisons Divided by Age, Sex, COVID-19, and Hyperlipidemia

The populations were defined in Table 1, with raw data in Table 4, and two sample proportion summary hypotheses with CIs were calculated for the proportion difference between populations. Mortality CIs between the male sex populations were considered statistically significant (p-value < 0.05): P1 and P5, P1 and P9, and P5 and P9. Mortality CIs between female sex populations were considered statistically significant (p-value < 0.05): P2 and P10, and P6 and P10. Mortality CIs between populations with age greater than or equal to 65 years old were considered statistically significant (p-value < 0.05): P3 and P11, and P7 and P11. Mortality CIs between populations with age less than 65 years old were considered statistically significant (p-value < 0.05): P4 and P12, and P8 and P12. In comparisons between populations of differences based on age and sex, the following populations had no statistical significance: P1 and P2 (p-value = 0.0904), P5 and P6 (p-value = 0.5272), and P9 and P10 (p-value = 0.6478). In comparisons between populations of differences based on age and sex, the following populations had statistical significance: P3 and P4 (p-value = 0.0251), with a CI between 1.12% and 12.75%; P7 and P8 (p-value < 0.0001), with a CI between 5.09% and 14.72%; and P11 and P12 (p-value < 0.0001), with a CI between 1.89% and 4.16%. CI: confidence interval, COVID-19: coronavirus disease 2019