Muscle Quality and Muscle Fat Infiltration in Relation to Incident Mobility Disability and Gait Speed Decline: the Age, Gene/Environment Susceptibility-Reykjavik Study.
BACKGROUND
Aging is associated with increased risk of reduced mobility. However, data on muscle components in relation to subjective and objective indicators of disability is limited.


METHODS
Data were from 2,725 participants (43% men) aged 74.8±4.7 years from the AGES-Reykjavik Study. At baseline, maximal isometric thigh strength (dynamometer chair), and midthigh muscle area and muscle fat infiltration were assessed with computed tomography. Usual 6 m gait speed and mobility disability were assessed at baseline and after 5.2±0.3 years. Incident mobility disability was defined as having much difficulty or unable to walk 500 m or climb-up 10 steps. A decrease of ≥0.1 m/s in gait speed was considered clinically relevant.


RESULTS
Greater strength and area were protective for mobility disability risk and gait speed decline. After adjustment for other muscle components, greater strength was independently associated with lower mobility disability risk in women odds ratios (OR) 0.78 (95% CI 0.62, 0.99), and lower decline in gait speed risk among both men OR 0.64 (0.54, 0.76), and women OR 0.72 (0.62, 0.82). Larger muscle area was independently associated with lower mobility disability risk in women OR 0.67 (0.52, 0.87) and lower decline in gait speed risk in men OR 0.74 (0.61, 0.91).


CONCLUSIONS
Greater muscle strength and area were independently associated with 15-30% decreased risk of mobility disability in women and gait speed decline in men. Among women, greater muscle strength was also associated with lower risk of gait speed decline. Interventions aimed at maintaining muscle strength and area in old age might delay functional decline.
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland. Department of Health Sciences and the EMGO Institute for Health and Care Research, Faculty of Earth and Life Sciences, VU University Amsterdam, The Netherlands. ilse.reinders@nih.gov.
Ilse
I
Reinders
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland.
Rachel A
RA
Murphy
Department of Social Medicine, School for Public Health and Primary Care (CAPHRI), Maastricht University, Maastricht, The Netherlands.
Annemarie
A
Koster
Department of Health Sciences and the EMGO Institute for Health and Care Research, Faculty of Earth and Life Sciences, VU University Amsterdam, The Netherlands.
Ingeborg A
IA
Brouwer
Department of Health Sciences and the EMGO Institute for Health and Care Research, Faculty of Earth and Life Sciences, VU University Amsterdam, The Netherlands. Department of Epidemiology and Biostatistics and the EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands.
Marjolein
M
Visser
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland.
Melissa E
ME
Garcia
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland.
Lenore J
LJ
Launer
Icelandic Heart Association Research Institute, Kopavogur, Iceland.
Kristin
K
Siggeirsdottir
Icelandic Heart Association Research Institute, Kopavogur, Iceland.
Gudny
G
Eiriksdottir
Department of Geriatrics, Landspitali National University Hospital and Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
Palmi V
PV
Jonsson
Icelandic Heart Association Research Institute, Kopavogur, Iceland. Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
Vilmundur
V
Gudnason
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland.
Tamara B
TB
Harris
D000273:Adipose Tissue / Q000378:metabolism*; D000368:Aged; D000375:Aging / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D059647:Gene-Environment Interaction; D006801:Humans; D008297:Male; D051346:Mobility Limitation; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000378:metabolism*
Epidemiology; Functional performance; Gait; Imaging; Muscle