Elsevier

Nutrition

Volume 25, Issue 6, June 2009, Pages 613-619
Nutrition

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

https://doi.org/10.1016/j.nut.2008.11.023Get rights and content

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.

Introduction

Changes in body composition observed with aging in longitudinal studies have included increases in body fat and loss of muscle mass [1], [2], [3], [4], [5], [6], [7]. Muscle mass decreases with increasing age, even when body weight remains stable [3], [8]. Cross-sectional studies in the elderly have reported an association between muscle strength and muscle quality change with aging [9], [10], [11], [12]. There exist limited data from longitudinal studies depicting such an association in population-based samples 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 associated with functional limitations [5], [15], but others have not [16]. Published data from longitudinal studies are also somehow contradictory. Broadwin et al. [4] found that increased percentage of body fat and decreased percentage of fat-free mass (FFM) were significantly associated with decreased functional ability in men and women. In contrast, in a longitudinal analysis of data from the Cardiovascular Health Study, it was found that low FFM was not predictive of disability (difficulty in walking or climbing stairs) in elderly men and women 65 to 100 y old at baseline. However, high body fatness was an independent predictor of mobility-related disability in older men and women [17].

Furthermore, it has been suggested that low muscle strength, but not low muscle mass, is associated with poor physical function in older men and women [18]. The inconsistencies in the findings of these studies [4], [5], [15], [16], [17], [18] may be due to differences in the study design, study population, and methodologies for assessing body composition and assessing muscle strength or physical function.

The aim of this study was to describe longitudinal changes in body composition and isometric muscle strength in a random sample of 75-y-old men and women from Göteborg who participated in the Nordic Research on Aging (NORA) study in 1990–1991 (NORA75) and were re-examined after 5 y at age 80 y in 1995–1996 (NORA80). Another aim was to investigate if body composition at age 75 y correlated with subsequent changes in muscle function during this 5-y prospective follow-up. We used these somewhat old longitudinal body composition data from one of our population-based cohorts of elderly subjects to investigate this because comparable body composition methods and muscle function data were available only in this cohort.

Section snippets

Population

This study is a part of the wider comparative NORA study on functional capacity and health among 75-y-old subjects. The study design and methodologic details have been reported elsewhere [19]. In short, a representative sample of 450 (191 men, 259 women) 75-y-olds living in Göteborg during 1991–1992 (NORA75) was invited and of them 323 (72%) participated in medical and laboratory investigations (143 men, 180 women). The participants did not differ from non-participants regarding sex, marital

Results

The anthropometric characteristics at age 75 y for the NORA75 cohort, the surviving participants of the NORA75 cohort in the NORA80 examination (longitudinal study population), and the study population for the present study are presented in Table 1. Although about half (38 men and 49 women) of the original longitudinal sample was used as the study population for this 5-y prospective study, participants did not significantly differ from the original NORA75 cohort in anthropometric

Discussion

Despite the relatively small sample, the study subjects are assumed to be representative of the population of their age group living in Göteborg during the study period, given the similarities in anthropometric characteristics with the larger NORA75 cohort. The data for this study were collected almost a decade ago, but in view of the very limited existing data on body composition and its relation to muscle strength in the elderly population, especially from population-based samples with

Conclusion

Fat-free mass and body water decreased significantly in both sexes over the 5-y period from 75 to 80 y of age. Declines in muscle strengths were evident for all muscle groups in both sexes for the period and it was more prominent in men. It was observed that body composition status at baseline, measured as FFM and FFMI, was a statistically significant predictor for decline in muscle strength, particularly in the extremities. This finding underscores the potential importance of FFM for

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