Body Composition and Physical Function in Individuals with Multiple Sclerosis and Age-BMI Matched Controls

Abstract

Persons with multiple sclerosis (PwMS) have reductions in physical function compared to healthy peers. In older adults, changes in body composition, specifically adiposity and lean mass, have been linked to reductions in physical function. The relation between body composition and physical function in PwMS is not well established. PURPOSE: The aim of this study was to determine if body composition, specifically a) adiposity (%Fat), b) lean mass of the legs (LEG), and c) leg lean mass to body mass ratio (LEG/BM) impacts lower extremity physical function (LEPF) differently in PwMS compared to controls. METHODS: PwMS (n = 33) and age (47.6±10.8 y) and BMI matched (27.3±6.8 kg/m2) controls (CON; n = 33) were measured for body composition via DXA and LEPF via 6-minute walk (WALK), Timed Up and Go (UPGO) and the Star Excursion Balance Test (SEBT) in the anterior (ANT), medial (MED) and posterior (POST) directions. RESULTS: Although not significant, PwMS had higher %Fat and lower LEG than CON (34.9±7.9% vs. 31.1±10.8%; 15.9±4.0 kg vs. 17.1±3.6kg, both p>0.05). However, LEG/BM was lower in PwMS compared to CON (0.21±0.3 kg vs. 0.23±0.4 kg, p=0.02). For all LEPF tests, compared to CON, PwMS had poorer performance; a 48% slower UPGO speed (4.0±1.0 sec vs. 8.3±5.7 sec, p<0.001), a 39% shorter WALK distance (1540.2±462.0 ft vs. 2136.5±347.9, p<0.001) and reduced reach lengths in the ANT, MED and POST (Right: 11.0%, 12.7%, 31.9%; Left: 7.9%, 22.1%, 32.3%, respectively, all p<0.05). Evaluating median splits for %Fat and LEG/BM, in the absence of any interactions, main effects were determined for: a) %Fat (p=0.01) and Group (p <0.001) such that higher %Fat and MS was associated with shorter WALK distance; and, b) LEG/BM (p = 0.069, p<0.001) and Group (both p<0.001) with a lower ratio and MS being associated with a slower UPGO speed and a shorter WALK distance. CONCLUSION: Comparing PwMS with age and BMI matched healthy controls, the ratio of leg lean mass to body mass was lower with a trend for a higher adiposity; as expected, all LEPF performance was poorer. Importantly, MS status and higher adiposity and lower ratio of leg mass to body mass combine to elicit the poorest LEPF. Body composition may be an important intervention target to preserve function in PwMS. Support: UIUC Research Board (PI: Fernhall)