Life-space mobility assessment in older people in Finland; Measurement properties in winter and spring

Background: Life-space mobility refers to the spatial area an individual moves through, the frequency and need for assistance. Based on the assumption that measurement scale properties are context-specific, we tested the scale distribution, responsiveness, and reproducibility of the 15-item University of Alabama at Birmingham Study of Aging Life-Space Assessment in older people in Finland, specifically accounting for season. Methods. Community-dwelling older men and women in central Finland aged 75-90 years were interviewed to determine life-space mobility (score range 0-120). Baseline (January-June 2012) and one-year follow-up data (January-June 2013; n = 806) from the cohort study "Life-space mobility in old age" were used to investigate the scale distribution and responsiveness over a period of one year. In addition, with a sub-sample in conjunction with the one-year follow-up, we collected data to study the two-week test-retest reproducibility (n = 18 winter and n = 21 spring 2013). Results: The median life-space mobility score at baseline was 64. The median change in score over the one-year follow-up was zero. However, participants reporting a decline in health (repeated measures ANOVA p =.016) or mobility (p =.002) status demonstrated a significantly larger decrease in life-space mobility score than those reporting no or positive changes over the year. The two-week intra-class correlation (ICC) coefficient was.72. Lower ICC was found in the winter than in the spring sample and for items that represent higher life-space levels. Conclusions: The test-retest reproducibility of the Life-Space Assessment was fair but somewhat compromised in the winter. Mobility of older people at the life-space levels of "town" and "beyond town" may be more variable. Life-space mobility was responsive to change, regardless of season. Further study is warranted to obtain insight in the factors contributing to seasonal effects. © 2014 Portegijs et al.; licensee BioMed Central Ltd.