About the research
Locomotor disability is a term that means difficulty in walking, climbing stairs and general ‘getting about’. It is prevalent in middle age and old age, however there is currently no brief, interval-level score developed specifically to measure the severity of locomotor disability in the general population.
In this research, the team set out to create such a score from five items related to physical functioning in a subscale of the The Short Form (36) Health Survey (SF-36) dataset, collected in North Staffordshire. Three of the five items related to walking, two related to stair-climbing.
They then assessed the scoring mechanism’s measurement properties by testing the data within a second dataset from the Welsh Health Survey which contained the same five items.
The resulting interval-level score was shown to fit well within other comparison datasets, including the Welsh Health Survey. This indicates that the score may be suitable for use in further research wishing to measure locomotor disability on a continuum.
Methodology
The researchers used the Rasch measurement model (Rasch 1980) to form an interval-level score and to assess the fit to this model. Repeatability, construct validity, and responsiveness of the new interval scale were examined.
The scoring mechanism was then applied to three external datasets, including the Welsh Health Survey (see details above). The fit to the scoring mechanism for the data was then assessed in the context of the Rasch model in all three datasets.
Publications
This study was published as Derivation and testing of an interval-level score for measuring locomotor disability in epidemiological studies of middle and old age in the journal Quality of Life Research, December 2009.
A presentation of the work was also made to the Society for Social Medicine in 2009.