The association between handgrip strength and functional outcomes in long COVID-19

In a recent longitudinal study published in Scientific Reports, researchers from Brazil investigated the potential association between dynapenia (loss of muscle strength and power) with functional outcomes in patients with long coronavirus disease 2019 (COVID-19).

They found that in patients with long COVID, low handgrip strength (HGS) is associated with worse functional outcomes. They further suggested the potential use of low HGS to indicate functional impairment in long COVID patients.

Study: Low handgrip strength is associated with worse functional outcomes in long COVID. Image Credit: Ralf Liebhold/Shutterstock.com

Background

Long COVID, characterized by persistent symptoms after infection with severe acute respiratory syndrome coronavirus 2 (SARS-VoV-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 an even higher prevalence in hospitalized individuals. Vulnerable populations, including middle-aged, female, Hispanic/Latino, and economically constrained groups, are at a higher risk of developing the disease.

Despite its impact, long COVID lacks a consensus definition and a standard biomarker or diagnostic tool. This often leads to potential underdiagnosis, particularly in low-and-middle-income countries (LMICs).

HGS is an indicator of dynapenia and is shown to be associated with various health outcomes, including cognitive disabilities, bone mineral density, depression, functional health, and mortality. In acute COVID-19, decreased HGS is an independent risk factor.

Using HGS as a simple, low-cost indicator could aid in identifying functional impairment, especially in LMICs lacking complex assessment tools.

Researchers in the present study aimed to investigate if individuals with a persistently low HGS after hospital discharge (following severe COVID-19 in early 2020) showed greater respiratory and functional impairments at 120 days.

About the studyTop of Form

The present longitudinal study was conducted at a hospital in Brazil from April to October 2020. It followed unvaccinated, adult COVID-19 patients of both sexes who tested positive for SARS-CoV-2 by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) during hospitalization. A total of 113 patients with a mean age of 48 years were included in the study, 54% of whom were female.

At the 120-day (D120) follow-up post-hospitalization, participants underwent assessments including functional capacity test, body composition, HGS, pulmonary function test, and respiratory muscle strength (RMS).

HGS and dynapenia (defined as HGS < 30 Kgf for males and < 20 Kgf for females) were measured using a hand-held digital dynamometer. Spirometry assessed pulmonary function, and RMS was evaluated with a digital manometer.

Outcomes were measured in terms of forced vital capacity (FEV), forced expiratory capacity at the first second of exhalation (FEV₁), maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP).

Functional capacity was assessed using the 6-minute walk test (6MWT), and body composition was determined through bioimpedance analysis.

Data were recorded electronically 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’s test, and a regression model.

Results and discussion

Out of the 113 long COVID patients, 22% exhibited dynapenia at D120 post-acute severe disease. Dynapenic individuals had lower muscle mass, reduced HGS, higher rates of intensive care unit admission and invasive ventilation during hospitalization, and higher BMI.

A greater proportion of dynapenic individuals showed a history of smoking and diabetes. Additionally, muscle mass between day one and D120 of dynapenic individuals was found to be reduced significantly (30.7 kg to 19.9 kg, p<0.001).

Dynapenia was also associated with worse respiratory function (FEV1, FVC, MIP, MEP), significantly diminished walking distance and a lower percentage of predicted walking distance on the 6MWT. Correlation and regression analyses confirmed the association between HGS and functional outcomes, independent of age.

The study’s limitations include a relatively small sample size and a short-term follow-up, preventing comprehensive longitudinal comparisons of HGS and other functional outcomes.

Additionally, the single-center design and the specific timeframe of individuals infected with SARS-CoV-2 in the early 2020s may limit the direct applicability of the results to individuals infected with more recent virus variants and with long-term health outcomes.

Conclusion

In conclusion, low HGS in long COVID patients, indicative of dynapenia, is linked to adverse health outcomes such as changes in pulmonary function, respiratory muscle strength, and exercise capacity.

A simple, cost-effective HGS measurement can be a practical biomarker for functional impairment in outpatient and primary care settings.

Recognizing dynapenia’s association with in-hospital outcomes months later enables timely patient stratification and risk prevention, potentially reducing comorbidities, delaying functional decline, improving prognosis, and expediting the return to daily activities.

This approach is particularly relevant for LMICs, enhancing healthcare accessibility, facilitating early screening, and managing long-term COVID patients.