Applied nutritional investigation Changes in body composition and its relation to muscle strength in 75-year-old men and women: A 5-year prospective follow-up study of the NORA cohort in Göteborg, Sweden Debashish K. Dey, M.D., M.P.H., Ph.D. a, *, Ingvar Bosaeus, M.D., Ph.D. b , Lauren Lissner, Ph.D. c , and Bertil Steen, M.D., Ph.D. a a Department of Geriatric Medicine, School of Public Health and Community Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden b Department of Clinical Nutrition, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden c Public Health Epidemiology Unit, School of Public Health and Community Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden Manuscript received April 26, 2008; accepted November 17, 2008. Abstract Objective: The purpose of this study was to explore the association between body composition in the elderly and subsequent changes in muscle strength during aging. Methods: This was a longitudinal study with a 5-y follow-up. Eighty-seven men (n = 38) and women (n = 49) from a random sample of 75-y-old subjects in the Göteborg part of the Nordic Research on Aging study who were investigated at ages 75 and 80 y and were free from any major diseases at baseline were included. Body composition was estimated from bioelectrical impedance. The maximal isometric strengths of handgrip, arm flexion, and knee extension were measured on the side of the dominant hand while a subject was in a sitting position in an adjustable dynamometer chair. Results: Fat-free mass decreased significantly (P  0.001) in both sexes, but more in men. Percentage of body fat increased only in men (P  0.05). Body height decreased in both sexes, but more in women (P  0.001). Declines in muscle strengths were evident for all muscle groups in both sexes but more prominent in men. It was observed that body composition status at baseline, measured as fat-free mass and fat-free mass index, was a statistically significant predictor for decline in muscle strength, particularly in the extremities. Conclusion: Fat-free mass at age 75 y was associated with lower 5-y decline in muscle strength. This finding underscores the potential importance of fat-free mass for maintaining functional ability during aging. © 2009 Published by Elsevier Inc. Keywords: Body composition; Muscle strength; Elderly; Longitudinal study Introduction Changes in body composition observed with aging in longitudinal studies have included increases in body fat and loss of muscle mass [1–7]. Muscle mass decreases with increasing age, even when body weight remains stable [3,8]. Cross-sectional studies in the elderly have reported an asso- ciation between muscle strength and muscle quality change with aging [9 –12]. There exist limited data from longitudinal studies depicting such an association in population-based sam- ples of free-living elderly [13,14]. The loss of muscle mass with aging, or sarcopenia, is hypothesized to be associated with metabolic, physiologic, and functional impairments and disability in the elderly [10]. However, available cross-sectional and longitudinal studies on the association between low muscle mass and physical function have provided inconsistent results. Some cross-sectional studies have shown that a reduced muscle mass and a greater fat infiltration in the muscle are associ- ated with functional limitations [5,15], but others have not * Corresponding author. Tel.: +1-317-374-2857; fax: +1-317-276- 6445. E-mail address: debashish_dk@yahoo.com (D. K. Dey). Nutrition 25 (2009) 613– 619 www.nutritionjrnl.com 0899-9007/09/$ – see front matter © 2009 Published by Elsevier Inc. doi:10.1016/j.nut.2008.11.023