[Evaluation of the best indicator of muscle mass in community-dwelling elderly persons]

Correlation between muscle strength and muscle mass, and their association with walking speed, in community-dwelling elderly Japanese individuals

OBJECTIVES

We aimed to assess the correlation between muscle strength and muscle mass based on sex and age, and their association with walking speed, which is a health predictor for independent living, in elderly Japanese individuals.

METHODS

The participants included 318 (111 men, 207 women) community-dwelling elderly Japanese individuals aged ≥65 years. Knee extension strength was assessed as an indicator of muscle strength, and bioelectrical impedance analysis was used to measure muscle mass. The maximum walking speed of participants was recorded. All measurements were categorized based on sex and age groups as follows: young-old (age, 65-74 years) and old-old (age, ≥75 years).

RESULTS

Appendicular muscle mass and knee extension strength decreased with age in both men and women. In men, knee extension strength showed significant positive correlations with leg and appendicular muscle mass in both young-old and old-old age groups. However, in women, only the old-old age group showed significant positive correlations between knee extension strength and leg and appendicular muscle mass. Muscle strength was significantly positively correlated with maximum walking speed in all groups, whereas muscle mass was not significantly correlated with maximum walking speed in men and women.

CONCLUSIONS

Muscle strength was significantly correlated with muscle mass in both age groups in men. However, in women, the correlation between muscle strength and muscle mass differed according to age. This finding suggests that the relationship between muscle strength and muscle mass differs according to sex and age. Muscle strength showed significant correlation with walking speed in both men and women in both age groups. These findings suggest that it is necessary to recognize that muscle strength is different from muscle mass, and that an individualized approach to prevent decline of muscle strength and muscle mass is necessary for health promotion in elderly.

Relationship between near-infrared spectroscopy, and subcutaneous fat and muscle thickness measured by ultrasonography in Japanese community-dwelling elderly

AIM

Near-infrared spectroscopy (NIRS) allows estimation of the percentage of body fat (%BF) regardless of the patient's posture; thus, it is useful for assessment of elderly patients with severe decline of basic activity who cannot hold a standing position. However, the accuracy by which the near-infrared light emitted from NIRS reflects subcutaneous tissue is unknown. The aim of this study was to assess how correctly NIRS reflects the subcutaneous fat and muscle thickness derived from ultrasonography in community-dwelling elderly.

METHODS

A total of 93 community-dwelling older adults aged 65 years and older were enrolled in this study (mean 75.8 years, 6.7 SD). Participants were assessed according to optical density (OD) measurements by NIRS, subcutaneous fat and muscle thickness by ultrasonography, and muscle strength. Pearson's correlation coefficients were calculated for each sex. Stepwise multiple regression analysis was used to identify factors that contributed to OD for each sex.

RESULTS

OD measured at the forearm and thigh were significantly correlated with subcutaneous fat thickness. In stepwise multiple regression analyses, subcutaneous fat thickness was found to be a significant determinant of OD in men (forearm β = -0.37, P = 0.01; thigh β = -0.63, P < 0.001) and women (forearm β = -0.50, P < 0.001; thigh: β = -0.52, P < 0.001).

CONCLUSIONS

These results suggest that NIRS can appropriately estimate fat-free mass. By adding other variables to OD as the predictive variable, skeletal muscle mass might be estimated in the elderly population.

[Relationship between occlusal force and preventive factors for disability among community-dwelling elderly persons]

AIM

Mastication ability is well documented as a risk factor for disability in the elderly. The aim of the present study was to assess occlusal force, one index of mastication ability, among elderly Japanese and clarify related factors through both physical measurements and questionnaires.

METHODS

Subjects were 372 community-dwelling persons (101 men, 271 women) aged 60-87 years and registered at five welfare centers for the aged in a metropolitan suburb. Occlusal force was measured with dental prescale/occluzer system. Physical measurements and questionnaires were performed to explore related factors.

RESULTS

Occlusal force was 502.4 N in men and 372.2 N in women. In the 60-69 and 70-79 age stratifications, men had significantly higher occlusal force than women. Occlusal force correlated significantly with age (r=-0.2, p<0.01), and number of residual teeth (r=0.6, p<0.01). After adjustment for age and the number of residual teeth, occlusal force had positive partial correlation with handgrip strength in men, and positive partial correlations with usual walking speed and body muscle mass, and negative partial correlation with timed up and go in women. From the questionnaire, high occlusal force was significantly associated with "can bite hard food" in both men and women; and with lifestyle factors ("walking regularly", "no smoking", and "alcohol consumption") in men; and with psychological factors ("intraoral satisfaction" and "no depression tendency") and physical factors ("can walk 1-km" and "can go out alone to distant places") in women.

CONCLUSION

Occlusal force was related to physical fitness, ability of movement, and lifestyle.