In a recent longitudinal study published in Scientific Reports, researchers from Brazil investigated the potential correlation between dynapenia (loss of muscle strength and power) and functional outcomes in patients with long coronavirus disease 2019 (COVID-19).
The researchers found that in patients with long COVID, low handgrip strength (HGS) was associated with poorer functional outcomes. They also suggested the possible use of low HGS to indicate functional impairment in patients with long COVID.
Long COVID, characterized by persistent symptoms following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a significant public health challenge. Symptoms include post-exertional malaise, fatigue, and neurocognitive and gastrointestinal issues.
The estimated global prevalence of the condition is 43%, with even higher prevalence among hospitalized individuals. Vulnerable populations, including middle-aged women, Hispanic/Latinx populations, and economically disadvantaged populations, are at higher risk of developing the disease.
Despite its impact, long COVID lacks a consensus definition and a standard biomarker or diagnostic tool, often leading to potential underdiagnosis, especially in low- and middle-income countries (LMICs).
HGS is an indicator of dynapenia and has been shown to be associated with various health consequences, including cognitive impairments, bone mineral density, depression, functional health, and mortality. Diminished HGS is an independent risk factor for acute COVID-19.
The use of HGS as a simple, cost-effective indicator could be helpful in identifying functional impairments, especially in LMICs where complex assessment instruments are lacking.
The researchers of the present study aimed to investigate whether individuals with persistently low HGS following hospital discharge (after severe COVID-19 in early 2020) exhibited greater respiratory and functional impairments after 120 days.
About the Study Top of Form
The present longitudinal study was conducted from April to October 2020 at a hospital in Brazil, observing unvaccinated adult COVID-19 patients of both sexes who tested positive for SARS-CoV-2 via reverse transcription quantitative polymerase chain reaction (RT-qPCR) during hospitalization. A total of 113 patients, with an average age of 48 years, were included in the study, 54% of whom were female.
At the 120-day follow-up (D120) after hospitalization, participants underwent functional capacity testing, body composition, HGS, pulmonary function testing, and respiratory muscle strength (RMS) testing, among other assessments.
HGS and dynapenia (defined as HGS < 30 kgf for men and < 20 kgf for women) were measured using a handheld digital dynamometer. Pulmonary function was assessed using spirometry, and RMS was evaluated using a digital manometer.
Results were measured based on forced vital capacity (FEV), forced expiratory volume in the first second of expiration (FEV1), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP).
Functional capacity was evaluated using the 6-minute walk test (6MWT), and body composition was determined using bioimpedance analysis.
The data were electronically recorded and analyzed for associations between HGS, respiratory function, and functional capacity. Statistical analysis included the Shapiro-Wilk test, Mann-Whitney test, chi-square test, Spearman test, and a regression model.
Results and Discussion
Among the 113 long COVID patients, 22% exhibited dynapenia at day 120 following acute severe illness. Dynapenic individuals had lower muscle mass, reduced HGS, higher frequency of intensive care unit admissions and invasive ventilation during hospitalization, as well as higher BMI.
A greater proportion of individuals with dynapenia had a history of smoking and diabetes. Additionally, it was found that muscle mass was significantly reduced between the first day and day 120 in dynapenic individuals (30.7 kg to 19.9 kg, p<0.001).
Dynapenia was also associated with poorer respiratory function (FEV1, FVC, MIP, MEP), significantly shortened walking distance, and a lower percentage of predicted walking distance in the 6MWT. Correlation and regression analyses confirmed the association between HGS and functional outcomes independent of age.
Limits of the study include a relatively small sample size and short-term follow-up, preventing comprehensive longitudinal comparisons of HGS and other functional outcomes.
Additionally, the single-center design and specific timeframe for individuals infected with SARS-CoV-2 in the early 2020s may limit the direct applicability of results to individuals infected with newer virus variants and experiencing long-term health consequences.
In conclusion, low HGS indicating dynapenia in long COVID patients is associated with adverse health consequences, such as changes in pulmonary function, respiratory muscle strength, and physical performance.
A simple, cost-effective HGS measurement can be a practical biomarker for functional impairments in outpatient and primary care settings.
Recognizing the correlation between dynapenia and hospital outcomes months later allows for timely patient stratification and risk prevention, potentially reducing comorbidities, delaying functional decline, improving prognosis, and accelerating the return to daily activities.
This approach is especially relevant for LMICs as it enhances healthcare accessibility, facilitates early detection screenings, and treats long COVID patients.