Increased risk of COVID-19-associated death in people under 70 with cardiovascular disease compared to the general population- A nationwide, registry-based study from Norway
Authors: Forster R B , Myklebust T.Å , Gravningen K M , Kvale R 
Published: October 2021

Abstract

Introduction
Reports from early in the pandemic suggested that older people with comorbidities were at increased risk of severe disease and death from COVID-19, including in Norway, where by September 2020 a majority of the COVID-19-associated deaths were in people with cardiovascular disease (CVD). However, it is uncertain if the increased risk seen in people with CVD could rather be explained by age and sex, both strong risk factors.

Purpose
To compare the incidence and mortality of COVID-19 in people with CVD to the general Norwegian population, controlling for age and sex, to better identify the risk of death in those with CVD.

Methods
We used data from the Norwegian Surveillance System for Communicable Diseases and Norwegian Cardiovascular Disease Registry to identify all test-positive cases and COVID-19-associated deaths in Norway up to June 30, 2020, as well as information on previously diagnosed CVD. CVD was defined as a composite of hypertension, myocardial infarction, stroke, heart failure and atrial fibrillation between 2012 to 2019. Standardized incidence and mortality ratios (SIR and SMR) were used to provide a measure of risk in people with CVD compared to the general population, stratified by age and sex.

Results
There were 8809 test-positive cases and 260 COVID-19-associated deaths, with 1015 cases in people with CVD and 137 deaths. In people with CVD there was decreased incidence (SIR 0.58, 95% CI 0.55–0.62), except for people over 90, who had increased risk (SIR 2.53 (1.66–3.66) for men and SIR 2.95 (2.20–3.85) for women) (Table 1). Despite the lower incidence, mortality was marginally increased (SMR 1.20 (1.01–1.42)) which was attributable to men 20–69 years (SMR 11.90 (6.70–19.26)). People aged 70 and above had the same risk of death from COVID-19 as the comparable general population without CVD.

Conclusion
This nationwide analysis from the first wave of the COVID-19 pandemic provides evidence that in people under 70 years with COVID-19, CVD was associated with an increased risk of death, despite lower incidence. We hypothesise the decreased incidence to be a result of social distancing and other measures adhered to in the beginning of the pandemic. However, those over 90 were not protected from this as they were more likely in a care setting where social distancing is more difficult, or a sign of increased testing in this group, which could introduce bias. Our analysis benefits from reliable, high-quality Norwegian registry data as well as being one of few nationwide studies not dependent on highly selected hospital reporting. The study is limited by relatively small numbers of deaths, especially in younger age groups, leading to possible residual confounding by age and sex as groups had to be pooled. Also, we did not control for other comorbidities. This analysis serves to support risk mitigation strategies in people with CVD and a basis to identify different risk patterns in later waves of the pandemic.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): Norwegian Institute of Public Health