If I had been around when Alexander the Great was looking for volunteers I definitely would have looked the other way. History tells us that he employed two men – Diognetus and Baeton – as ‘bematists’ to accurately count their steps and thereby measure the distance between cities as his army marched through Asia. Quite how they managed to achieve astonishing levels of accuracy is sadly not recorded, but that is one job I would certainly not have signed up for! Strange as it may seem, but accurate step counting is back in fashion!
The proposal I am going to discuss in this article is that accurate monitoring of physical activity should now be adopted as a standard outcome measure for research in arthritis and sponyloarthritis.
I make no claim to originality here. When I was a trainee in Newcastle upon Tyne in the early 90s, David Walker introduced me to an activity tracker called the NUMACT monitor. Using this monitor, his group quantified the improvements in the actual daily mobility of RA patients after knee injection (70%), and after NSAID use (50%). They then showed a significant (79%) improvement in mobility in OA patients six months after total knee arthroplasty. He compared these results to questionnaires that ask about physical mobility (such as the Nottingham Health Profile) and reported significant differences. Until recently, there had been very few other such studies in patients with arthritis, and I believe that it is about time we followed his forward thinking approach. Before we take a look at these studies, let’s review the rationale for going to all this trouble.
The stated aim of the International Classification of Functional Disability and Health (ICF) is to “put every person in a context: functioning and disability are results of the interaction between the health conditions of the person and their environment”. They suggest that a new framework for outcome measurement is required, and in the area of assessment of general physical mobility we need to look at the issue through three different ‘lenses’. The first is to use self-reported assessment of problems in daily function using questionnaires such as the HAQ. The second is to measure physical activity under ‘laboratory’ situations (e.g. a ‘six minute walk test’) and the third is to monitor physical activity in the patient’s natural environment (at home, work etc.). This has to be a positive move for patients, as it will help to ‘re-set’ our target towards one that will get our patient back participating fully in their ‘natural environment’ (work, home and leisure).
At the moment the only one of these included as a ‘core outcome measure’ by EULAR/ASAS is the questionnaire assessment. There is no doubt that this is very useful and relatively easy to collect as part of a research project. But ultimately the goal of our treatment has to be to get the person back to the optimal level of function in real life. So can a questionnaire such as the HAQ accurately tell us when the patient’s function has returned to normal? Certainly not: there is a ‘floor effect’ that will not detect changes between no disability and low-moderate disability. And how can you really take account of aids and adaptations? Does the HAQ correlate well with 6 minute walk tests or activity monitoring studies? The research here is still a bit patchy, but it appears that these three ways of measuring of function may have quite different stories to tell.
We should perhaps eat a little humble pie and learn from our orthopaedic colleagues. In the past the success or failure of hip replacement was mainly judged by measuring standard surgical outcomes such as mortality and morbidity but for some years now they have realised that with a younger and more active group of patients the expectations of a good outcome are higher. Surgical success rates are higher than patient satisfaction rates for both hip and knee arthroplasties, and actual improvements in physical activity can lag even further behind. This is a problem, as we have always assumed that an important goal of these operations is to return the patient to a relatively high level of physical functioning. A study by deGroot et al (2008) looked at recovery after hip and knee arthroplasties using all three methods: the SF36 questionnaire, the 6 minute walk test and monitoring daily activity using an accelerometer device. This study reported substantial improvement in self-reported physical activity whilst daily physical activity had not improved to anywhere near the same extent. This surprising result will hopefully lead to renewed efforts to improve rehabilitation programmes.
I also look across at the nearby cardiac rehabilitation clinic with some admiration. Research has shown that a good ‘medical’ outcome after acute myocardial infarction is often followed by a significant loss of mobility and participation in normal activities, and the success of cardiac rehabilitation programmes has been most impressive. What amazes me is how well motivated their patients seem to be in sticking to the rehab plan! I think that our patients who continue to suffer from pain and stiffness due to their chronic arthritis probably need a little more help and encouragement using technology such as activity monitors. In a small but important randomised study Talbot (2003) showed that in patients with symptomatic knee OA, a 23% increase in monitored physical activity was seen in the group given a pedometer with a specific rehabilitation plan whilst those who were given normal education advice showed an actual fall in performance. A striking difference between groups was also evident in tests of isometric muscle strength (the ‘laboratory’ test). This sort of study should give us hope that outcomes can be improved by employing technology in targeted rehabilitation programmes.
So, if we’re all agreed that this is a laudable thing to try and measure, what then should we be measuring and what is already known in this area? ‘Physical Activity’ has a technical meaning in Sports Medicine that many readers may not be aware of: it is all about energy expenditure in METs rather than just measuring steps or miles. If we are talking about achieving high intensity in daily physical activities we need to measure more than the number of steps. In my next post we’ll have a closer look at the approach chosen by a couple of recent studies. I’ll also be having a look at some of the technology out there with an emphasis on the scientific validation of the different monitors. And of course, I must emphasise that at the moment I’m just looking at general function rather than specific joint movements of relevance to the specific disease in question (such as the electronic goniometric glove, for instance).
And by the way, I didn’t know what a Bematist was either – but I thought it might get your attention!