Table 1.

Summary of the epidemiological studies concerning the association between hypertension and COVID-19

					Hypertension as a risk factor
First author, country [Reference]	Design	Definition of hypertension	Number and population	Outcome	Univariate analysis	Multivariable-adjusted analysis	Note
Zhou, China [4]	Retrospective cohort study	N.A.	191 adult inpatients (>18 years), median age 56.0 years	In-hospital death	Yes (48% vs. 23%; p = 0.0008)	No (not selected)	137 patients were discharged and 54 died in hospital. Hypertension was the most common comorbidity (n = 58, 30%). Older age, high Sequential Organ Failure Assessment score, and high D-dimer level were selected as independent explanatory factors for in-hospital death among 171 patients with complete data.
Grasselli, Italy [5]	Retrospective case series	N.A.	1591 patients admitted to ICU, median age 63 years	COVID-19	N.A.	N.A.	Hypertension was the most common comorbidity (n = 509, 49% of the 1,043 individuals with comorbidity data). Patients with hypertension were older than those without hypertension (median age, 66 vs. 62 years, p < 0.001). ICU mortality was 26%. The mortality of older patients (≥64 years) was higher than that of younger patients (≤63 years) (36% vs. 15%, p < 0.01).
Richardson, US [6]	Retrospective case series	ICD-10 coding No diagnostic criteria shown	5700 inpatients, median age 63 years	COVID-19	N.A.	N.A.	Hypertension was the most common comorbidity (n = 3026, 56.6%). 553 patients (21%) died in hospital; 134 were 18–65 years and 419 were >65 years.
Shi, China [11]	Retrospective cohort study	N.A.	487 inpatients, mean age 46 years	Severity on admission	Yes (53.1% vs. 16.7%; p < 0.001)	Yes (OR, 2.71; CI,1.32–5.59; p = 0.007)
Li, China [12]	Ambispective cohort study	ICD-10 coding No diagnostic criteria shown	548 inpatients, median age 60 years	1) Severity on admission 2) In-hospital death	1) Yes (38.7% vs. 22.2%; p < 0.001) 2) N.A.	1) Yes (OR, 2.01; CI, 1.27–3.17) 2) No(not selected)	As independent predictors for mortality, male, ≥65 years, high white blood cell count, high lactate dehydrogenase value, cardiac injury, hyperglycemia, and high dose corticosteroid were selected.
Simonnet, France [13]	Retrospective cohort study	N.A.	124 patients admitted to ICU, median age 60 years	Need for IMV	Yes (OR, 2.81; CI, 1.25–6.30; p = 0.012)	No (OR, 2.29; CI, 0.89–5.84; p = 0.08)	Definition of obesity and severe obesity: BMI > 30 and 35 kg/m2, respectively. The prevalence of obesity and severe obesity was 47.6% (n = 59) and 28.2% (n = 35), respectively. As BMI increased, the proportion of the patients who received IMV increased (chi-square test for trend, p < 0.01). On multivariable logistic regression analysis, severe obesity was an independent risk factor (OR, 7.36; CI, 1.63-33.14; p = 0.021).
Cai, China [14]	Retrospective cohort study	N.A.	383 inpatients, median age: nonsevere patients (n = 292, 76.2%) 44.5 years, severe patients (n = 91, 23.8%) 61 years	Progression to severe COVID-19	Yes (23.08% vs. 12.67%; p = 0.02)	Done, but not shown	Definition of obesity: BMI > 28 kg/m2. The prevalence of obesity was 10.7% (n = 41). Compared with the patients with BMI 18.5–23.9 kg/m2, obese patients showed 3.40-fold odds (CI, 1.40–2.86; p = 0.007) of outcome by multiple logistic regression analysis after adjusting for several factors including hypertension.
Wu, China [15]	Retrospective cohort study	N.A.	201 inpatients with COVID-19 pneumonia, median age 51 years	1) Development of ARDS 2) Death among patients with ARDS (n = 84)	1) Yes (27.4% vs. 13.7%; p = 0.02) 2) Yes(36.4% vs. 17.5%; p = 0.05)	No (analysis unclear)	Hypertension raised the risk of ARDS development (HR, 1.82; CI, 1.13–2.95; p = 0.01]), but not the risk of progression from ARDS to death (HR, 1.70; CI, 0.92–3.14; p = 0.09). However, these were based on bivariate Cox regression analysis, and the methodology, in particular whether other factors were adjusted, was unclear.
Zheng, China [19]	Retrospective cohort study	Consensus statement from the IDF	66 patients with metabolic associated fatty liver disease, mean age 47 years	Progression to Severe COVID-19	N.A.	Done, but not shown	Definition of obesity: BMI > 25 kg/m2. The prevalence of obesity was 68% (n = 45). The hypertension prevalence between obese and non-obese patients did not differ significantly (35.6% vs. 14.3%, p = 0.089). In the logistic regression model, obesity was shown to be a risk factor after adjusting for age, sex, smoking, diabetes, hypertension, and dyslipidemia (OR, 6.32; CI, 1.16–34.54; p = 0.033).

BMI body mass index, CDC Centers for Disease Control and Prevention, CI 95% confidence interval, COVID-19 coronavirus disease 2019, HR hazard ratio, ICU intensive care unit, ICD-10 International Classification of Diseases-version 10, IDF International Diabetes Federation, IMV invasive mechanical ventilation, ARDS acute respiratory distress syndrome, N.A. not available, OR odds ratio