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, 9 (9), e031584

Skeletal Muscle Function and Need for Long-Term Care of Urban Elderly People in Japan (The Bunkyo Health Study): A Prospective Cohort Study


Skeletal Muscle Function and Need for Long-Term Care of Urban Elderly People in Japan (The Bunkyo Health Study): A Prospective Cohort Study

Yuki Someya et al. BMJ Open.


Purpose: The proportion of elderly individuals (age ≥65 years) in Japan reached 27.7% in 2017, the highest in the world. A serious social problem in a super-aged society is the rise in the number of elderly people who need long-term care (LTC), which is mainly due to cerebrovascular disease, dementia, age-related frailty, falls and fractures, and joint disease. We hypothesised that decreased muscle mass, muscle strength and insulin sensitivity are the common risk factors for these diseases related to needing LTC. We developed a prospective cohort study of elderly subjects in an urban community to test this hypothesis. The primary objective is to prospectively investigate associations between muscle mass, muscle strength, and insulin sensitivity and incidence of main disease and risk factors of needing LTC. The primary outcomes are the incidence of cerebrovascular disease and cognitive decline.

Participants: Participants were 1629 people aged 65-84 years living in 13 communities in an urban area (Bunkyo-ku, Tokyo, Japan). Average age was 73.1±5.4 years.

Findings to date: We obtained baseline data on cognitive function, cerebral small vessel disease (SVD) determined by brain MRI, body composition, bone mineral density, arteriosclerosis, physical function, muscle mass, muscle strength and insulin sensitivity. Mild cognitive impairment and dementia were observed in 18.1% and 3.3% of participants, respectively. The prevalence of cerebral SVD was 24.8%. These characteristics are similar to those previously reported in elderly Japanese subjects.

Future plans: We will ask participants about their health status, including incidence of cerebrovascular disease, falls, fractures and other diseases every year by mail. We plan to re-evaluate cognitive function, brain MRI parameters and other parameters at 5 and 10 years after the baseline evaluation. We will evaluate whether low muscle function (muscle mass, muscle strength or insulin sensitivity) is a risk factor for cognitive decline or cerebrovascular disease.

Keywords: community based study; insulin sensitivity; long-term care; muscle mass; muscle strength.

Conflict of interest statement

Competing interests: None declared.


Figure 1
Figure 1
Geographical location of Bunkyo-ku in Japan. Left: Japan is divided into 47 prefectures. The location of Tokyo is indicated by a circle. Centre: Tokyo is a prefecture that includes 23 special wards, 26 cities, 5 towns and 8 villages. Bunkyo is one of the special wards (Bunkyo-ku in Japanese). It located in east Tokyo, as indicated by the circle. Right: Bunkyo-ku includes 68 communities and has 227 902 residents (source of map;
Figure 2
Figure 2
Experimental protocol.
Figure 3
Figure 3
Flow chart of the participant recruitment process.
Figure 4
Figure 4
Distribution of the elderly population in this cohort, Bunkyo-ku and Tokyo. The proportion of elderly individuals in each age group (age 65–84 years) in this cohort, Bunkyo-ku and Tokyo are presented.

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