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Pre-existing hypertension not an independent risk factor for in-hospital COVID-19 mortality

Pre-existing hypertension does not appear to be independently associated with in-hospital mortality among patients with COVID-19

Pre-existing hypertension is not an independent risk factor for in-hospital mortality among patients with COVID-19. This was the key finding of an analysis of a COVID-19 patient registry by researchers from the Institute of Cardiovascular Science, University College London, UK.

Early in the COVID-19 pandemic, Chinese researchers reported that after adjustment for confounders, patients with hypertension had a two-fold increased risk of mortality compared to those without the disease. However, in contrast, another Chinese study, suggested that neither hypertension nor elevated blood pressure were independent risk factors for death or acute respiratory distress syndrome (ARDS)/respiratory failure, but that hypertension marginally increased the risk of severe COVID-19 infection. Based on these early findings, a 2020 systematic review which analysed the effect of co-morbidities on COVID-19, concluded that underlying diseases, including hypertension, respiratory system disease and cardiovascular disease, may be risk factors for severe COVID-19 infection. Further studies however, have been mixed, with one indicating that hypertension may be an independent risk factor for all-cause mortality in patients with COVID-19, whereas another US-based study of over 2,000 patients identified several clinical and hospital-level risk factors that may be associated with death in critically ill patients with COVID-19, but did not include hypertension.

Given the uncertainty over whether pre-existing hypertension is an independent risk factor for mortality in COVID-19, the UK team turned to the CAPACITY-COVID register, which was specifically designed to collate detailed information regarding cardiovascular risk factors and complications from COIVD-19 during hospital admission. Participants in the database were adults and the analysis was based on the presence of confirmed COVID-19 infection and documented pre-existing hypertension. Using regression analysis, the primary outcome focused on the association between pre-existing hypertension and in-hospital mortality and models were adjusted for several factors including age, sex, diabetes and kidney disease.

Pre-existing hypertension and in-hospital mortality

The analysis included 9,197 individuals with a median age of 69 years (60.6% male) of whom, 48.3% had pre-existing hypertension.

In-hospital mortality occurred in 22% of participants with more deaths recorded in those with pre-existing hypertension (26% vs 18.2%, p < 0.001). In the unadjusted models, the presence of pre-existing hypertension was associated with an increased odds of mortality (odd ratio, OR = 1.57, 95% CI 1.42 – 1.74). But when the models were fully adjusted for known confounders such as age, this effect was attenuated and became non-significant (aOR = 0.97, 95% CI 0.87 – 1.10).

With respect to anti-hypertensive treatment, in fully adjusted models and when the data were pooled, both angiotensin converting enzyme inhibitor (ACEi) and angiotensin receptor blocker (ARB) drugs, tended to have a protective effect on in-hospital mortality (aOR = 0.88, 95% CI 0.78 – 0.99).

The authors concluded that after appropriate adjustment and in contrast to earlier findings, pre-existing hypertension does not independently confer an increased risk of death among patients hospitalised with COVID-19. They added that despite some early concerns, the use of both ACEi and ARB drugs appeared to offer some degree of protection against in-hospital mortality.

McFarlane E et al. The impact of pre-existing hypertension and its treatment on outcomes in patients admitted to hospital with COVID-19 Hypertens Res 2022

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