Smokers’ hand grip strength predicts respiratory event risk

LOS ANGELES – Hand grip strength is independently predictive of risk for respiratory events in smokers who have or are at risk for chronic obstructive pulmonary disease, a single-center study showed.

“Measures of lung function, including spirometry, are used as the main descriptors of COPD severity and prognosis,” said in advance of the annual meeting of the American College of Chest Physicians. “These measurements, as important as they are, need to be improved, in order to develop better risk and prognostic models of disease, to identify subgroups at higher risk of poor outcomes... With work, have proved that simple physical tests could be part of future prognostic models.”

Interest has grown in developing multidimensional models to predict respiratory prognosis. Such models include BODE (body mass index, and air flow obstruction, dyspenea, and exercise capacity), ADO (age, dyspnea, and air flow obstruction), and DOSE ( dyspnea, airflow obstruction, smoking status, and exacerbation frequency).

In patients with or at risk for COPD, the University of Michigan Health System, Ann Arbor, tested the associations of hand grip strength with measures of body composition such as pectoralis muscle area and extent of subcutaneous fat, imaging phenotypes, and lung function.

The researchers obtained demographic, clinical, lung function, hand grip strength, and imaging data from 441 smokers with and without COPD participating in the Genetic Epidemiology of COPD Study (COPDGene) at National Jewish Health in Denver.

Correlations between measures of lung function, imaging phenotypes, body composition, and hand grip strength were analyzed in univariate analysis and in multivariate linear models. The association between hand grip strength and exacerbations was analyzed at enrollment and during an average follow -up of 2.6 years.

Hand grip strength was similar across groups categorized by spirometry severity and was not associated with emphysema severity.

After adjustment for demographics, smoking history, smoking intensity, comorbidities, and lung imaging phenotypes, however, grip strength was associated with pectoralis muscle area ( increase of 3.9 kg per 1 standard deviation of pectoral muscle area) and subcutaneous adipose tissue ( a decrement of 5.1 kg per 1 SD of subcutaneous adipose tissue). These associations were independent of body mass index and the presence of emphysema.

During follow-up, hand grip strength was associated with exacerbations ( risk ratio, 0.94/ 1- kg increment on grip strength) and incident exacerbations ( incident risk ratio, 0.92/ 1- kg increment on grip strength) in models adjusted for other factors known to be associated with exacerbations.

They have confirmed prior hypotheses that it is not just weight or BMI that matters (to risk of exacerbations), but how much muscle and how much fat are contributing to our patient’s high or low BMI.

Hand grip testing can be challenging in this patient population. Still, asking relevant questions about (patients’) physical fitness will help us to understand better our patients’ needs. It can also give more attention to the extra pulmonary structures included in the numerous chest CT scans that order for our patients. These imaging studies include important and easy to discover clues to identify patients at higher risk of exacerbations – those with low muscle and low hand grip could benefit from close follow-up.

There are certain limitations of the study, including the selection of the measures of body composition. The used analysis of chest CTs instead of the gold standard of dual absorptiometry or other methods such as bioelectrical impedance. A final limitation is that we tested a selected group of participants in a cohort study, not a representative sample of the population, [with a] low burden of emphysema and fewer African American participants.