MUSCLE STRENGTH-RELATED INDEXES EFFECTIVE IN EXTENDING THE DURATION OF ADL INDEPENDENCE IN THE VERY OLDER AGE GROUP

¹Gunma Paz University, Health Sciences, Takasaki, Japan

Background: Extending healthy life expectancy is an important issue. Okinawa Prefecture in Japan, which once had the highest life expectancy in the world, now has a life expectancy below the average for the country. However, in Ogimi Village, an isolated district, life expectancy is significantly higher, and the percentage of elderly persons aged 85 years or older who are independent in ADLs is much higher than the Japanese average. A search has been made for factors that increase healthy life expectancy among the elderly in this area.　
We are conducting a new 9-year cohort study to collect new data as well as to take over data from residents of this region, where cohort study data have existed for more than 50 years.　
Interestingly, we have found little evidence of age-related or physical inactivity sarcopenia among the elderly in this region. However, the cohort results suggest the presence of some muscle strength-related factor in the prolonged period of ADL independence. It is desirable to specifically identify this factor.

Purpose: To develop a new index combining physiological muscle tissue assessment and kinematic assessment, and to clarify the influence of muscle strength index on prolongation of the duration of ADL independence in very older persons.

Methods: The study design was a cohort study. Subjects were older adults aged 85 years or older (as of 2014, n=140) in Ogimi Village, Okinawa, Japan. Inclusion criteria were the ability to walk independently, independence in personal ADLs, no motor dysfunction affecting ADLs, and no cognitive impairment in daily life. Random sampling was used for sampling, with a sample-to-total rate of 50%. The outcome was the duration of ADL independence (in months), and explanatory variables were gender, age, weight, BMI, lifestyle-related diseases (presence of medication for diabetes, hypertension, dyslipidemia), and history of falls, as well as effective muscle mass, which is the difference in grip strength between the left and right hand divided by muscle mass percentage. Analysis was conducted by dividing the subjects into two groups based on the mean value of effective muscle mass, one low group and one high group, and the effects of these groups were calculated, evaluated, and verified by a generalized linear model(GLM) using the maximum likelihood estimation method by logarithmization. Statistical analysis was using IBM-SPSSv21.

Results: The GLM was significant at the 95% confidence interval for the bisection of the independent period was the effective muscle mass in women, B = -4.455, standard error = 2.1109, 95% Wald confidence interval, -8.592 to -0.317 (p = 0.035). Execution muscle mass in men, simple muscle mass and grip strength in men and women separately did not show significance at the 95% Wald confidence interval.

Conclusions: The actual contractile capacity of effective muscle tissue, may be related to increased healthy life expectancy in very old persons only in the female group.

Implications: In older adults who remain active, it is difficult to estimate the duration of independent living by assessing muscle mass. The ratio of muscle output to muscle mass that can actually be exerted determines the duration of independence.

Funding acknowledgements: Gunma Paz University Research Institute

Keywords:
Very old people
Independent living
Effective muscle mass

Topics:
Health promotion & wellbeing/healthy ageing/physical activity
Older people
Research methodology, knowledge translation & implementation science

Did this work require ethics approval? Yes

Institution: Gunma Paz University

Committee: Gunma Paz University Ethics Review Board

Ethics number: 21－25