Exercising more than once a week for those over the age of 50 has been linked to a lowered risk of coronavirus disease 2019 (COVID-19) hospitalization by 60%. An international team of researchers has found that physical activity involving muscle training can be protective against severe infection.
The study “Muscle Strength Explains the Protective Effect of Physical Activity against COVID-19 Hospitalization among Adults aged 50 Years and Older” is available as a preprint on the medRxiv* server, while the article undergoes peer review.
The researchers suggest older adults should try to be regularly physically active. “Because of the high prevalence of physical inactivity in the general population, especially at older age and during the COVID-19 pandemic, the present findings highlight the need to encourage older adults to regularly engage in physical activity.”
Collecting survey data
The researchers collected data from two datasets in adults 50 years or older living in 27 different European countries. The first dataset involved 136,000 individuals with survey information collected every 2 years between 2004 and 2017. The second dataset was specialized for COVID-19, with data collected from 52,000 individuals. The primary outcome was the hospitalization for COVID-19.
A total of 3,139 individual data was used for the analysis. Of this number, 266 were COVID-19 positive, and 66 were hospitalized.
Survey data also captured the amount of exercise engaged in by older adults. They were measured by low-to-moderate physical activity, such as gardening and walking, to vigorous physical activity, such as sports or a job requiring manual labor. Muscle strength was measured through a participant’s handgrip strength.
The researchers also collected information on different variables that could also be linked to COVID-induced hospitalization. For instance, height and gender may influence a person’s level of physical activity.
As severe COVID-19 is more prevalent among people with comorbidities, they included factors such as body mass index, cardiovascular disease, high blood pressure, cancer, and more.
Muscle strength explains the link between physical activity and COVID-19 hospitalization
Results showed a correlation between higher age, heart disease, and muscle strength and being admitted to the hospital because of the coronavirus.
The chance for hospitalization increases the older a participant is. Participants that were 65-75 years of age and 75-96 years of age had a higher chance of becoming hospitalized.
Participants who rarely exercised or engaged in any type of physical activity had a greater risk of COVID-19 hospitalization than people who were physically active more than once a week.
When associations were reanalyzed, only muscle strength and rate of hospitalization remained significant.
Having higher muscle strength decreases the risk for COVID-19 hospitalization. Muscle strength helped explain why approximately 24% of participants who were classified as physically inactive were hospitalized.
The researchers note that self-reporting physical activity levels could have compromised measurement validity.
In addition, the team attempted to measure covariates such as height and comorbidities that could have influenced the connection between physical activity and hospitalization. However, there is always a possibility that other variables may be guiding this connection.
It’s also difficult to establish a causal relationship when it remains ambiguous whether physical activity affects health conditions or health conditions affect physical activity.
Future larger-scale studies are needed to examine whether the associations of physical activity with severe COVID-19 may be also explained by the links between physical activity and other relevant chronic conditions,” write the research team.
It also remains unknown how exercise changes during COVID-19 and whether a decrease in the infection period directly leads to increased hospitalization.
Many participants could also have been COVID-19 positive and not have known it, causing a misclassification bias. The researchers suggest the lack of awareness early on could explain why every association with hospitalization — except muscle grip strength — was nonsignificant.
However, the team believes their findings add to the current literature on this topic by presenting evidence on the protective effects of physical activity on COVID-19 hospitalization. Muscle grip strength may be the mediator of this link.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.