Japan is a country where the percentage of the elderly is most rapidly increasing, with the aged population accounting for 28.8% in 2020, and the number of people in need of nursing care is also increasing [1]. Among recipients of the long-term nursing care aged ≥ 65 years, locomotive organ disorders, such as fractures/falls and articular diseases, are the major reasons that lead patients to opt for nursing care, accounting for approximately 10% and 30% in men and women, respectively [1]. A condition with mobility impairment caused by locomotive organ disorders is referred to as “locomotive syndrome (LS)” [2]. Engaging in regular exercise, appropriate nutrition, and being active are important to avoid LS [3]. Cunningham et al. have shown that active elderly people have reduced risks including those for fractures, falls, and impairment in activities of daily living (ADL) [4]. The Japanese Ministry of Health, Labour and Welfare established numerical targets for health promotion in individuals aged ≥ 65 years, including that the daily number of steps and percentage of individuals who regularly exercise for men and women should be 7000 steps and 58% and 6000 steps and 48%, respectively [5]. However, according to the current data from the National Health and Nutrition Survey regarding the number of steps and percentage of individuals who regularly exercise among men and women (5396 steps and 41.9% and 4656 steps and 33.9%, respectively, in 2019), the targets have not been reached [6]. In 2020, people all over the world had restrictions imposed upon them to go out due to the spread of the coronavirus disease 2019 (COVID-19). Ammar et al. have reported decreases in the number of days of walking and physical activity per week and an increase in daily sedentary time in adults aged ≥ 18 years, which included older adults [7]. Similarly, a survey of healthy Japanese people aged ≥ 65 years reported that the time of physical activities was reduced by approximately 35%, compared with that before the spread of the infection [8]. A survey of Irish people who received ambulatory medical services and cocooning (age, ≥70 years) has shown that their physical and mental health conditions were aggravated by restrictions to going out [9]. Decreased physical activities because of the ongoing COVID-19 pandemic may have negative effects on health and quality of life in older adults in the future and warrant efforts to prevent nursing-care dependency.

LS is associated with decreases in motor functions, such as reduced muscular strength, balance function, and joint mobility [2] [3]. Makizako et al. have reported that age-related changes in physical abilities differed between men and women, especially in the walking speed of women [10]. LS and frailty are more frequent in women than in men [11] [12]. Janssen et al. have documented that among people aged ≥ 60 years, the prevalence of sarcopenia in women was higher than that in men [13]; thus, it is important to consider health maintenance and promotion in elderly women.

Muscle mass also decreases in an age-related manner [14] [15]. Janssen et al. have reported that the regression curve of age-related muscle mass loss in the lower limbs had a significantly larger slope than that in the upper limbs [14]. Fried et al. have included decreased muscle strength (handgrip strength) and walking ability as part of the diagnostic criteria for frailty [12]. Additionally, it has been reported that elderly people with frailty had decreased muscle mass [16] [17]. Reduced skeletal muscle mass is reportedly associated with impaired functioning and ADL disorders [13]. Therefore, thoroughly examining body composition and muscle strength in addition to maintaining and improving them is necessary to prevent older adults from requiring nursing care. Genton et al. performed longitudinal measurements and reported that subjects aged ≥ 75 years at baseline lost more body weight and fat-free mass (FFM) than those aged 65 - 74 years [18]. Therefore, it is necessary to separately ascertain the body size and compositions in young (yE group) and old elderly people (oE group).

Hayashida et al. have reported that the association between muscle mass and strength in the lower limbs differ depending on sex and age [15], and Reed et al. have reported that the correlation between muscle circumference and strength in the upper limbs is different from that in their lower limbs [19]. However, there are a few studies comparing muscle mass-strength correlation patterns in the upper and lower limbs between elderly people and young people.

In the present study, we aimed to clarify the characteristics of body compositions in the yE (age, 65 - 74 years) and oE (age, ≥75 years) groups of elderly Japanese women and to compare muscle mass-strength of the above correlation patterns in elderly with those in young people to provide valuable information for the prevention of motor function deterioration in old age.

In this study, we characterized body compositions of elderly women after dividing

the elderly participants into the yE group and the oE group and compared relationships between muscle mass and muscle strength between elderly and young women.

The physique data shown in Table 1 indicated that height, weight, and BMI of the elderly and young participants in this study did not differ significantly from those of Reference A and B values (National Health and Nutrition Survey, 2017) [26], confirming that both the elderly and young groups had physiques within ranges of respective general Japanese populations.

The elderly group had a shorter height, similar weight, lower FFM and total body water, and a higher FM than those of the young group (Table 2).

As shown in Figure 1, the weight of the yE group tended to be slightly higher and that of the oE group was significantly lower than that of the young group. Given the fact that the FFM of the yE group remained comparable, the higher weight tendency of the yE group seems to be attributable to the higher FM. In the oE group, the body weight was significantly lower than those of the young and yE groups; the FFM and FM were reduced by approximately 11% and 28% compared with those of the yE group, respectively. That is to say, the weight decrease of the oE group was attributable to decreases in both FFM and FM. In a 5 - 12-year follow-up study in women aged 60 years on average, Hughes et al. have reported that the FFM did not change appreciably over time and decreased only 0.1 kg [27]. Genton et al. have shown that the FFM and body weight were maintained at 65 - 74 years of age but decreased significantly at ≥75 years [18]. These previously reported findings are consistent with ours.

As shown in Table 2, the percent body fat and FM of the elderly group were significantly higher than those of the young group, and the increase of the yE group was particularly noticeable. Regional FM values of the yE group accumulated markedly in the trunk, and the WHR of the yE group was also significantly larger than that of the young group. The WHR is considered to reflect the accumulation of abdominal fat (visceral fat) [28]. Buffa et al. have shown that the visceral fat accumulates with age [29]. Genton et al. have indicated significant age-associated increases in the waist circumference and WHR in elderly women aged 65 - 74 years [18]. Therefore, the FM increase in the yE group is presumably due to the age-associated accumulation of visceral fat.

Meanwhile, the FM of the oE group was significantly lower than that of the yE group. The FM has been shown to decrease rapidly after 80 years of age in cohort studies of Japanese women by Seino et al. [30] and in American people by Ding et al. [31]. The results of these previous studies suggest that the FM decline started in the oE group in the present study. Furthermore, the FM of the oE group was 5.5 kg lower than that of the yE group, and the body region of the decrease was as follows: 0.8 kg in the upper limbs; 1.6 kg in the lower limbs; and 3 kg in the trunk. Since the fat in the upper and lower limbs is considered to be mainly subcutaneous fat, the data suggest that the FM decrease of the oE group reflects not only the visceral fat decrease but also the subcutaneous fat decrease.

The comparisons of water in the body showed no significant differences in total body water, ICW, and ECW between the yE group and the young group; however, the total body water of the oE group was significantly lower than that of the young group or the yE group. The total body water difference between the oE group and the young or yE group was accounted for by not only the ICW decrease but also the ECW decrease. Therefore, while the total body water of the elderly group decreased with age, no major changes occur in the yE group, as was the case for FFM, and both ICW and ECW decreased in the oE group (Table 2). Lesser et al. have reported that the total body water and ICW in elderly people were lower than those in young people [32]. In contrast, Schoeller has reported that it was not clear whether the age-associated decrease in total body water was due to the ICW decreased and/or the ECW decrease [33]. The results of the present study showed that both ICW and ECW of the oE group were lower than those of the young or yE group, suggesting that the age-associated change in total body water of the elderly group includes ECW as well as ICW.

Regarding muscle mass measurements (Table 2), the upper-limb and trunk muscle mass values of the yE group remained comparable to those of the young group, but the decrease in the lower-limb muscle mass was noticeable, and muscle mass values in the upper and lower limbs and the trunk of the oE group were lower. Muscle mass in older adults decreased in an age-dependent manner [14] [18] [30]. In a cross-sectional study, Janssen et al. have reported muscle mass in both the upper and lower limbs decreased with aging and in particular, in the lower part of the body [14]; these findings are consistent with ours. A previous study has shown that scores of all the handgrip strength, Five-Times-Sit-to-Stand test, and walking speed in elderly Japanese people decreased in an age-dependent manner, and the walking speed decrease in women was particularly noticeable [10]; these findings suggest the age-associated changes in the lower limbs are larger than those in other regions of the body. Physical activities have also been reported to decrease with aging and the decrease is particularly noticeable in women [34]. In addition to the age-associated muscle mass decrease, the reduced physical activities may also be accountable for the muscle mass decrease of the oE group.

The relationship between muscle mass and muscle strength differed between the elderly and young groups (Figures 2(A)-(D)). In the young group, positive correlations between muscle mass and muscle strength were noted for both the upper and lower limbs, indicating that the muscle strength increases with the muscle mass. In the elderly group, a significant positive correlation between muscle mass and muscle strength was found for the upper limbs, as in the young group; however, such a correlation was not found for the lower limbs. These data indicate that the muscle mass, particularly in the lower limbs, does not directly reflect the muscle strength in the elderly group. Goodpaster et al. conducted a three-year longitudinal study on lower-limb muscles in elderly people and have reported that both the muscle mass and muscle strength of the lower limbs decreased year by year but the latter decreased more rapidly than the former [35]. The rapid decrease in the lower-limb muscle strength may explain, at least in part, why no association between muscle mass and muscle strength of lower limbs was found in the elderly group in the present study. Reed et al. have reported that the correlation between muscle strength and muscle cross-sectional area in the lower limbs was weaker than that in the upper limbs [19]. Lexell et al. have shown that the lower-limb muscle fiber density in people in their 70s and 80s was lower than that in young people [36], and pennation angles of muscle fibers may have effects on the muscle fiber density decrease [37]. The muscle fiber pennation angle has been shown to decrease as age increases, and the pennation angle in elderly is significantly smaller than that in young people [38] [39]. Kubo et al. compared the muscle thickness and the pennation angle in upper and lower limbs between elderly and young people and have reported that the lower-limb muscle thickness and pennation angle of the elderly group were significantly smaller than those of the young group, but the upper-limb muscle thickness and pennation angle did not differ between the two groups [40]. Effects of these changes in muscle architecture on exertion of force may underlie the absence of association between muscle mass and muscle strength in the lower limbs.

These results revealed that age-related changes in body composition in the elderly differ depending on the age group; in the oE group, the changes were particularly large, and both FFM and FM decreased. The FM decrease of the oE group was presumably caused by the subcutaneous as well as the visceral fat decrease. In the yE group, there was a remarkable reduction in the lower-limb muscle mass, and upper-limb, trunk, and lower-limb muscles all decreased in the oE group. While positive correlations between muscle mass and muscle strength in the upper and lower limbs were found in the young group, no such a correlation in the lower limbs was found in the elderly group, indicating that the muscle mass changes are not directly reflected in muscle strength changes in elderly people. Therefore, to prevent motor function deterioration in old age, it is necessary to maintain muscle strength and mass to prevent the loss of muscle quality.

This research was supported by Kobe Women’s University Grant. We would like to express our sincere appreciation to all the participants in the study.

The authors declare no conflicts of interest.

Nishi, N.N., Tanaka, N. and Hirano, N. (2022) Characteristics of Body Composition and Relationship between Muscle Mass and Muscle Strength among Elderly Women in Different Age Groups. Advances in Aging Research, 11, 135-149. https://doi.org/10.4236/aar.2022.115010