U.K. researchers have established that hypertension is associated with a 22% greater risk of severe COVID-19, with the odds of severe COVID-19 unaffected by medication type.
Hypertension “appears to be one of the commonest comorbidities in COVID-19 patients”, explained the authors of a new study, published in PLOS ONE. The authors highlighted that previous research had shown that hypertension was more prevalent in severe and fatal cases compared with all cases of COVID-19.
They pointed out, however, that whether hypertensive individuals have a higher risk of severe COVID-19, compared with nonhypertensives, and whether the absolute level of systolic blood pressure or the type of antihypertensive medication is related to this risk, remained “unclear.”
To try to answer these questions, the research team, led by University of Cambridge researchers, analyzed data from 16,134 individuals who tested positive for COVID-19 (mean age 65.3 years, 47% male, 90% white), 40% were diagnosed with essential hypertension at the analysis baseline – 22% of whom had developed severe COVID-19.
Systolic blood pressure (SBP) was categorized by 10–mm Hg ranges, starting from < 120 mm Hg up to 180+ mm Hg, with the reference category defined as 120-129 mm Hg, based on data from the SPRINT study, which demonstrated that intensive SBP lowering to below 120 mm Hg, as compared with the traditional threshold of 140 mm Hg, was beneficial. Diastolic blood pressure was categorized by 10–mm Hg ranges, starting from < 60 mm Hg up to 100+ mm Hg with 80-90 mm Hg being the reference category.
In their analyses the researchers adjusted for age, sex, body mass index, ethnicity, smoking status, diabetes status, socioeconomic status, and inflammation (C-reactive protein [CRP]), as these were proposed as potential confounders. To assess the direct effect of hypertension on COVID-19, they also adjusted for intermediate variables, including cardiovascular comorbidities and stroke, on the causal pathway between hypertension and severe COVID-19.
Majority of effect of hypertension on severe COVID-19 was direct
The unadjusted odds ratio of the association between hypertension and severe COVID-19 was 2.33 (95% confidence interval, 2.16-2.51), the authors emphasized. They found that, after adjusting for all confounding variables, hypertension was associated with 22% higher odds of severe COVID-19 (OR, 1.22; 95% CI, 1.12-1.33), compared with normotension.
Individuals with severe COVID-19 were marginally older, more likely to be male, and more deprived, the authors said. “They were also more likely to be hypertensive, compared with individuals without severe COVID-19, and a greater proportion of individuals with severe COVID-19 had cardiovascular comorbidities.”
The majority of the effect of hypertension on development of severe COVID-19 was “direct,” they said. However, a modest proportion of the effect was mediated via cardiovascular comorbidities such as peripheral vascular disease, MI, coronary heart disease, arrhythmias, and stroke. Of note, those with a history of stroke had a 47% higher risk of severe COVID-19 and those with a history of other cardiovascular comorbidities had a 30% higher risk of severe COVID-19, the authors commented.
Of the total of 6,517 (40%) individuals who had a diagnosis of essential hypertension at baseline, 67% were treated (41% with monotherapy, 59% with combination therapy), and 33% were untreated.
There were similar numbers of severe COVID-19 in each medication group: ACE inhibitors, 34%; angiotensin receptor blockers (ARBs), 36%; and “other” medications 34%.
In hypertensive individuals receiving antihypertensive medications, there was a “J-shaped relationship” between the level of blood pressure and risk of severe COVID-19 when using a systolic blood pressure level of 120-129 mm Hg as a reference – 150-159 mm Hg versus 120-129 mm Hg (OR 1.91; 95% CI, 1.44-2.53), > 180+ mm Hg versus 120-129 mm Hg (OR 1.93; 95% CI, 1.06-3.51).
The authors commented that there was no evidence of a higher risk of severe COVID-19 until systolic blood pressure “exceeded 150 mm Hg.”
They said it was an interesting finding that “very well-controlled” systolic blood pressure < 120 mm Hg was associated with a 40% (OR, 1.40; 95% CI, 1.11-1.78) greater odds of severe COVID-19. “This may be due to reverse causality, where low systolic blood pressure levels may indicate poorer health, such that the occurrence of severe COVID-19 may be related to underlying disease rather than the level of SBP per se,” they suggested.
The J-shaped association observed remained after multiple adjustments, including presence of known cardiovascular comorbidities, which suggested a possible “real effect” of low SBP on severe COVID-19, “at least in treated hypertensive individuals.”
Their analyses also identified that, compared with a “normal” diastolic blood pressure (80-90 mm Hg), having a diastolic blood pressure higher than 90 mm Hg was associated with higher odds of severe COVID-19.
The association between hypertension and COVID-19 was “amplified” if the individuals were treated and their BP remained uncontrolled, the authors pointed out.
There did not appear to be any difference in the risk of severe COVID-19 between individuals taking ACE inhibitors and those taking ARBs or other antihypertensive medications, the authors said.
Better understanding of underlying mechanisms needed
Individuals with hypertension who tested positive for COVID-19 had “over twice” the risk of developing severe COVID-19, compared with nonhypertensive individuals, the authors said.
They highlighted that their findings also suggest that there are “further effects” influencing the severity of COVID-19 beyond a “dichotomous” diagnosis of hypertension.
“Individuals with a higher-than-target systolic blood pressure may be less healthy, less active, suffering more severe hypertension, or have developed drug-resistant hypertension, all suggesting that the effects of hypertension have already had detrimental physiological effects on the cardiovascular system, which in turn may offer some explanation for the higher risk of severe COVID-19 with uncontrolled SBP,” they explained.
“Hypertension is an important risk factor for COVID-19,” reiterated the authors, who emphasized that a better understanding of the underlying mechanisms driving this increased risk is warranted in case of “more severe strains or other viruses” in the future.
The authors have declared no competing interests.
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