[Life-space of community-dwelling older adults using preventive health care services in Japan and the validity of composite scoring methods for assessment].

OBJECTIVE

Life-space is a spatial measure of mobility defined by the distance a person routinely travels to perform activities over a specific time period. Life-space assessment (LSA) has been widely applied, but measurement properties have not been investigated in a Japanese population. The purpose of this cross-sectional study was to describe distributions of maximal life-space and to clarify the validity of composite scores of an LSA scale among community-dwelling older adults using preventive health care services in Japan.

METHODS

Surveys were conducted between November 2007 and February 2008 with a specially prepared Japanese LSA version. The sample was composed of 2,147 participants using preventive health care services provided by the Japanese long-term care insurance system, all being aged 65 and over, with adequate cognitive functions and living at home in the community (29.5% men, mean age +/- [SD] 79.4 +/- 6.9 years). First, the levels of life-space, based on how far a person had travelled on leaving his or her place of residence during the month preceding the assessment, were investigated. Second, LSA scores were calculated considering the degree of independence as well as frequencies for individuals at each level, then descriptive statistics were checked. Finally, it was tested whether the scores could be related to external criteria and functional or socio-psychological variables stated in previous studies.

RESULTS

Sixty-four percent of individuals attained the highest level of life-space (i.e. outside town). The average of the composite scores was 51.4 +/- 25.2 points and the distribution was almost normal. The dispersion of the scores tended to be large. Values correlated with the hierarchical mobility level classification as an external criterion (0.539). As hypothesized, the scores were correlated with age (-0.296), functional mobility (time up and go test) (-0.387), and instrumental activities of daily living (0.533), and were discriminated by sex, depressive mood, and perceived health status, in the expected directions.

CONCLUSIONS

The present study described the extent of life-space in older adults using preventive health care services in Japan, and provided preliminary support for criterion-related (concurrent) and construct validity of scores with the LSA Japanese version. The LSA composite scoring method may have advantages for detecting differences in life-space among individuals, as compared to simply using the maximal level attained.