key: cord-339919-4ko4lwjz
authors: Cook, T. M.
title: The importance of hypertension as a risk factor for severe illness and mortality in COVID‐19
date: 2020-05-09
journal: Anaesthesia
DOI: 10.1111/anae.15103
sha: 
doc_id: 339919
cord_uid: 4ko4lwjz

The virus responsible for COVID-19 binds to the angiotensin converting enzyme-2 (ACE-2) receptor [1]. Several articles have noted that hypertension is a risk factor for COVID-19 [2-7]. It is currently difficult to distinguish between hypertension as an independent risk factor in COVID-19 from one that co-varies with other patient factors such as age and cardiovascular disease. It is difficult from individual reports to determine whether hypertension is a risk factor for development of symptomatic disease or hospitalisation or for more severe disease. Reviewing the literature that reports rates of hypertension amongst included patients indicates a consistent association with more severe disease and increased mortality.

. It is currently difficult to distinguish between hypertension as an independent risk factor in COVID-19 from one that co-varies with other patient factors such as age and cardiovascular disease. It is difficult from individual reports to determine whether hypertension is a risk factor for development of symptomatic disease or hospitalisation or for more severe disease. Reviewing The prevalence of hypertension in China is approximately 23% [8] and in Italy, 26% [9] . These reports therefore do not provide robust evidence as to whether hypertension is a risk factor for developing symptomatic COVID-19 requiring hospitalisation. Yang et al. [10] reported that hypertension was not more common in those in China with COVID-19 than the general population.

However, in all the above reports, hypertension is notably associated with poor outcome from COVID-19. The current data do not clarify the mechanism of this increased risk, for instance whether it is due to hypertension itself or treatment, nor whether it is associated with the use of ACE inhibitors and angiotensin-2 type-I receptor blockers, though this has been previously suggested [11] .

The limitation of this analysis is that in several of the studies, final patient outcomes are uncertain as patients' hospitalisation or ICU stay has not been completed.

Hypertension is included in many reports as a 'risk factor' for COVID-19 but there has been a lack of clarity as to whether this means risk factor for acquiring the disease, the severity of disease or for poor outcomes. It is also easy to dismiss high blood pressure as a risk factor as other factors such as underlying cardiovascular or respiratory disease might initially seem more likely to impact outcome, as they do for other critical illnesses. However, the evidence shown here indicates that hypertension is consistently associated with severe or critical illness, and with death.

There is increasing understanding that severe COVID-19 causes considerable vascular abnormalities including widespread microthrombotic and macrothrombotic events, renal and cardiac failure. The association of hypertension with its potential microvascular disease, with more severe disease and poor outcomes from COVID-19, is therefore an important consideration. 

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