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Physical inactivity is associated with a higher risk for severe COVID-19 outcomes

Abstract Objectives To compare hospitalisation rates, intensive care unit (ICU) admissions and mortality for patients with COVID-19 who were consistently inactive, doing some activity or consistently meeting physical activity guidelines.

Methods We identified 48 440 adult patients with a COVID-19 diagnosis from 1 January 2020 to 21 October 2020, with at least three exercise vital sign measurements from 19 March 2018 to 18 March 2020. We linked each patient’s self-reported physical activity category (consistently inactive=0–10 min/week, some activity=11–149 min/week, consistently meeting guidelines=150+ min/week) to the risk of hospitalisation, ICU admission and death after COVID-19 diagnosis. We conducted multivariable logistic regression controlling for demographics and known risk factors to assess whether inactivity was associated with COVID-19 outcomes.

Results Patients with COVID-19 who were consistently inactive had a greater risk of hospitalisation (OR 2.26; 95% CI 1.81 to 2.83), admission to the ICU (OR 1.73; 95% CI 1.18 to 2.55) and death (OR 2.49; 95% CI 1.33 to 4.67) due to COVID-19 than patients who were consistently meeting physical activity guidelines. Patients who were consistently inactive also had a greater risk of hospitalisation (OR 1.20; 95% CI 1.10 to 1.32), admission to the ICU (OR 1.10; 95% CI 0.93 to 1.29) and death (OR 1.32; 95% CI 1.09 to 1.60) due to COVID-19 than patients who were doing some physical activity.

Conclusions Consistently meeting physical activity guidelines was strongly associated with a reduced risk for severe COVID-19 outcomes among infected adults. We recommend efforts to promote physical activity be prioritised by public health agencies and incorporated into routine medical care.

Data availability statement No data are available.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

Introduction The US Centers for Disease Control and Prevention (CDC) has identified risk factors for severe COVID-19, including advanced age, sex (male) and the presence of underlying comorbidities, such as diabetes, obesity and cardiovascular disease.1 However, there are no data regarding the effect of regular physical activity (PA) on COVID-19 outcomes, even though a lack of PA is a well-documented underlying risk factor for multiple chronic diseases, including those associated with severe COVID-19.

The US Physical Activity Guidelines call for all adults to engage in at least 150 min/week of moderate to vigorous physical activity (MVPA). Similar guidelines have been promoted in many countries based on strong evidence that regular PA results in a broad range of health benefits. It is reasonable to expect regular PA may mitigate poor COVID-19 outcomes. It is well known that immune function improves with regular PA, and those who are regularly active have a lower incidence, intensity of symptoms and mortality from various viral infections. Regular PA reduces the risk of systemic inflammation, which is a main contributor to lung damage caused by COVID-19. Additionally, exercise benefits cardiovascular health, increases lung capacity and muscle strength, and improves mental health. These are mechanisms by which regular PA could play an important role in mitigating the severity of the COVID-19 pandemic, in addition to its beneficial effects on multiple chronic diseases.

During the pandemic, populations across the globe have been advised to stay home and avoid contact with individuals outside of one’s household. Lockdowns and other measures that constrain travel have restricted access to gyms, parks and other venues where people can be active. In the USA, education about the benefits of PA and advice to maintain or increase PA during the pandemic has been essentially absent. While prepandemic levels of PA were generally insufficient, pandemic control measures have likely had the unintended consequence of reducing PA even more. Indeed, early studies indicated a significant reduction in PA levels since the beginning of the pandemic.

In this study, we used an electronic health record (EHR) that captured self-reported PA behaviours prior to the pandemic to evaluate the hypothesis that consistently meeting guidelines prior to diagnosis is associated with more favourable COVID-19 outcomes among infected adults. If regular PA is shown to be a protective behaviour for COVID-19, efforts should be made to enable and encourage regular PA as a means of protecting individuals from severe COVID-19 outcomes.

Methods Study design This is a retrospective observational study in which PA was documented in the EHR in the 2 years preceding the March 2020 pandemic lockdown.

Setting This study was conducted at Kaiser Permanente Southern California (KPSC), which is an integrated healthcare system that serves approximately 4.7 million residents in Southern California at 15 medical centres. Racial/ethnic make-up, neighbourhood education and household income are generally similar to the area population. KPSC uses a comprehensive EHR that links all laboratory results, healthcare visits and diagnoses in both inpatient and outpatient settings and even outside the system.

Study cohort Inclusion criteria consisted of KPSC health plan members aged 18 years and older with a positive COVID-19 test or diagnosis between 1 January 2020 and 21 October 2020. Participants were continuously enrolled at KPSC for at least 6 months prior to their COVID-19 diagnosis. We required patients to have at least three outpatient visits with an exercise vital sign (EVS) measure between 19 March 2018 and 19 March 2020 to increase the likelihood that the assessment captured regular PA habits.

Exercise vital sign The EVS is used at every outpatient encounter within the KPSC system since 2009 and has been described elsewhere. Briefly, trained medical assistants or nurses ask patients two questions about their typical exercise habits over the previous 2 months or more during the intake at each outpatient visit: ‘On average, how many days per week do you engage in moderate to strenuous exercise (like a brisk walk)?’ and ‘On average, how many minutes do you engage in exercise at this level?’. Response choices for days are 0–7, and minutes are recorded as 0, 10, 20, 30, 40, 50, 60, 90, 120 and 150 or greater. The responses are recorded in each patient’s EHR and minutes per week of MVPA are calculated. The EVS has been shown to have good face and discriminant validity.

Three categories of PA were created for this study based on the US Physical Activity Guidelines: consistently meeting guidelines (EVS >150 min/week at all assessments during the study period), consistently inactive (EVS 0–10 min/week at all assessments) and some activity (EVS 11–149 min/week or those with variability in their EVS measures).

Data analysis The primary outcomes examined were hospitalisation, admission to the intensive care unit (ICU) and death due to COVID-19. Patient demographics, utilisation, clinical characteristics and comorbidities among different PA groups were compared using χ² test for categorical variables, exact test for categorical variables with a count <5 (none of the cell expected values were less than 1 and fewer than 20% of the cell expected values were less than 5) and the Kruskal-Wallis test for continuous variables. Covariates included age, sex and race, along with underlying medical conditions associated with increased risk for severe illness from COVID-19 as defined by the CDC.2 These underlying conditions included a history of cancer (primary and metastatic), chronic kidney disease, chronic obstructive pulmonary disease, cardiovascular disease (including myocardial infarction, congestive heart failure, peripheral vascular disease and cerebrovascular disease), history of organ transplant, obesity (body mass index (BMI) 30–39 kg/m2) and class 3 obesity (BMI ≥40 kg/m2), pregnancy, current smoking status and diabetes. In addition, we included history of hypertension and an emergency department visit or hospitalisation in the 6 months prior to COVID-19 diagnosis as covariates. We conducted logistic regressions to estimate the ORs (and 95% CIs) for the association of these factors with the EVS categories, with separate models for each of the outcomes. Data were analysed using SAS (V.9.4 for Windows; SAS Institute)

Patient and public involvement Patients and the public were not involved in the design or conduct of this study.

Results We identified 103 337 patients with a diagnosis of COVID-19 or positive result on PCR testing during the study period. Of these, 84 377 were 18 years or older and continuously enrolled in the KPSC health plan during the 6 months prior to their COVID-19 diagnosis. Among these, 48 440 patients had three or more EVS measurements within the 2 years prior to the California pandemic lockdown on 18 March 2020, which comprised the analytical cohort for this study. The majority of patients (61.2%) in our cohort had five or more EVS measures in that 2-year time frame (see online supplemental table).

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