Whatever the cause, many people with a long-term disability move less than other people of a similar age. Short-term measurement with accelerometers can measure this, but it is a snap-shot and daily fluctuations will lead to difficulties in interpretation.
In a study on 56 (reducing to 48 over 30 months) people with multiple sclerosis, activity was measured over a 5-7 day period (23+ hours each day) every six months for 30 months. The activity meter was worn on the arm. There were correlations as expected with other measures, including degree of cerebral atrophy. Change could be detected, and change in activity correlated with increasing cerebral atrophy.
The paper makes no mention of how many people were in wheelchairs, but some if not many must have been, and it seemed responsive across the range.
The measure could clearly be used in patients with many other disabling conditions such as Parkinson’s disease, stroke, motor neurone disease, muscular atrophies and non-neurological disorders such as osteoarthritis of hips and knees, and muscular atrophy.
Reduced activity is also seen in chronic spinal pain, fibromyalgia and chronic fatigue syndrome. In these conditions a similar measure could look at patterns of activity over time, and be used to help patients increase their activity in a controlled way, avoiding so-called “boom and bust” cycles.