Daily electromyography in females with Parkinson's disease: A potential indicator of frailty

Abstract

Females with Parkinson's disease (PD) are at increased risk for frailty, yet are often excluded from frailty studies. Daily electromyography (EMG) recordings of muscle activity can dissociate stages of frailty and indicate functional decline in non-neurological conditions. The purpose of this investigation was to determine whether muscle activity can be used to identify frailty phenotypes in females with PD. EMG during a typical 6.5-h day was examined in biceps brachii, triceps brachii, vastus lateralis and biceps femoris on less-affected PD side. Muscle activity was quantified through burst (>2% maximum exertion, >0.1 s) and gap characteristics (<1% maximum exertion, >0.1 s). Differences across frailty phenotype (nonfrail, prefrail, frail) and muscle (biceps brachii, BB; triceps brachii, TB; vastus lateralis, VL; biceps femoris, BF) were evaluated with a 2-way repeated measure ANOVA for each burst/gap characteristic. Thirteen right-handed females (mean = 67 ± 8 years) were classified as nonfrail (n = 4), prefrail (n = 6), and frail (n = 3) according to the Cardiovascular Health Study frailty index (CHSfi). Frail females had 73% decreased gaps and 48% increased burst duration compared with nonfrail. Decreased gaps may be interpreted as reduced muscle recovery time, which may result in earlier onset fatigue and eventually culminating in frailty. Longer burst durations suggest more muscle activity is required to initiate movement leading to slower movement time in frail females with PD. This is the first study to use EMG to dissociate frailty phenotypes in females with PD during routine daily activities and provides insight into how PD-associated motor declines contributes to frailty and functional decline.

Introduction

Frailty is a complex geriatric syndrome that is often clinically characterized by five criteria: (1) Weight loss; (2) Reduced endurance; (3) Slowed gait speed; (4) Muscle weakness; and (5) Exhaustion, resulting in functional dependence (Fried et al., 2001). According to Fried et al. (2001), frailty can be assessed in terms of three phenotypes, or categories of frailty severity, which are defined by the sum of the five individual frailty criteria (i.e., 0: nonfrail, 1 or 2: prefrail, and 3–5: frail). Although frailty can exist independently, it may also co-exist in older adults with progressive neurological disorders, such as Parkinson's disease (PD) (Roland, Jakobi, Jones, & Powell, 2012). Co-morbidities and clinical symptoms interact between frailty and PD making identification of frailty in persons with PD challenging to diagnose (Powell, 2008). Few studies have examined how to identify frailty in the PD population (Ahmed et al., 2008, Lauretani et al., 2012).

Electromyography (EMG) recordings provide a measure of muscle activity that governs movement associated with sustaining physical function. EMG detects the bioelectrical activity associated with muscle contractions that produce movements and reveals important neural changes associated with aging and decline in physical function (Clark et al., 2010a, Clark et al., 2011). Previous work from our laboratory has determined portable EMG devices as a viable means to record muscle activity in older adults during daily life and offer a method to detect frailty-, disease- and age-related differences in muscle activity required to execute movement (Harwood et al., 2011, Howe and Rafferty, 2009, Jakobi et al., 2008, Kern et al., 2001, Roland et al., 2013, Theou et al., 2010, Theou et al., 2011).

Recent investigations (Theou et al., 2010) have used EMG to quantify periods of muscle quiescence (gaps) and muscle activity (bursts) in frail older females as they went about their routine daily activities. As the level of frailty advanced the number of gaps increased while the duration of gaps decreased, and the number of bursts decreased while the burst duration increased (Theou et al., 2010). This study indicated that EMG can be used to identify persons of different frailty phenotypes. Quantification of muscle quiescence during daily life has also provided insight into underlying asymmetric functional decline and differential change in performance in males and females with PD (Roland et al., 2013). EMG recordings of daily muscle activity that detect stages of frailty have not yet been quantified in females with PD. Females with PD are an under-represented group in research, yet they experience greater functional decline (Leveille et al., 2000, Paganelli et al., 2006, Smith and Baltes, 1998) and often become frail more so than age-matched males (Fried et al., 2001). This suggests there is a need to investigate the implications of frailty on muscle activity during daily function in females with PD. Evidence demonstrates factors that contribute to frailty in non-neurological populations, such as age and physical activity, are not associated with frailty in persons with PD (Roland, Cornett, Theou, Jakobi, & Jones, 2012). Therefore, additional factors should be considered, such as muscle activity to better understand frailty within PD.

This study aims to determine if daily muscle activity differs between frailty phenotype in females with PD to facilitate identification of frailty. It is hypothesized that greater periods of muscle quiescence and shorter periods of muscle activity will occur and this change will be exacerbated as females with PD progress across frailty phenotypes. These changes in muscle characteristics will be observed, despite the presence of PD. Understanding how muscle activity changes across frailty phenotypes may help to inform interventions aimed at delaying frailty progression in females with PD. Application of this new-knowledge may improve clinical practice by providing an indicator of change in muscle activity that precipitates increased disability in PD.