Clinicians and researchers at the Institute of Myology have just published an article in the journal Neurology* concerning the use of accelerometers to assess the impact of a treatment by measuring the daily physical activity of patients with idiopathic inflammatory myopathies (IIM). Jean-Yves Hogrel, Director of the Laboratory of Physiology and Neuromuscular Evaluation, discusses the results of this pilot study.
Can you explain the concept of daily physical activity?
Physical activity is defined as any movement produced by skeletal muscles, responsible for an increase in energy expenditure during daily life (day and night). Physical activity particularly includes movement (e.g. walking), housework, leisure activities, planned exercise and rehabilitation. The level of daily activity reflects, among other things, a patient’s ability to move. There are currently different ways to assess daily physical activity in patients’ homes such as questionnaires and, more recently, portable devices (such as accelerometers) that can be worn on the ankle, waist, wrist, and that allow an objective measure of physical activity daily**.
What is actigraphy and how does it allow this type of measurement?
Actigraphy is defined as the analysis of signals (e.g. acceleration) in order to evaluate motor activity. Three types of actigraphy can be distinguished: i) actigraphy to characterise movement in a controlled environment. For example, at the Institute of Myology, an accelerometer is attached to a belt in order to characterise walking in terms of regularity, symmetry, etc. This gives us information about the quality of walking during, for example, a 6-minute walk test, where the distance walked is evaluated; ii) actigraphy designed to evaluate daily physical activity over relatively long periods up to several consecutive months, 24 hours a day; iii) actigraphy to thoroughly analyse signals to evaluate, for example, physical inactivity, quality of sleep, time spent walking, time spent in mild, moderate, vigorous physical activity etc.
Objectively measuring physical activity allows to estimate the consequences of a pathology on patients’ lives and to measure its evolution over time. It is also a means of assessing a person’s lifestyle and the risks associated with, for example, insufficient physical activity. It is therefore a behavioural measure that includes multiple factors such as physical abilities, motivation, socio-cultural environment, the seasons, days of the week, etc. For example, if a person has a habit of spending the day sitting in a chair and never moving, even if cared for, that person will not necessarily move more. Actigraphy is therefore also a very useful tool for evaluating the effectiveness of an intervention to increase the physical activity of patients in order to protect them, for example, from complications associated with a sedentary lifestyle.
Specifically, how did you proceed for this study?
For the newly published pilot study, we equipped 5 patients with inflammatory myopathies who are followed at the Institute of Myology by Olivier Benveniste, Yves Allenbach and Océane Landon-Cardinal (Inflammatory Myopathies and Innovative Therapies Team, Myology Centre for Research – Department of Internal Medicine and Clinical Immunology, Hôpital Pitié-Salpêtrière). In this family of pathologies, muscles degenerate rapidly and patients feel tired, weak and can quickly end up with disabilities. Treatment usually allows them to recover an almost complete muscle function.
The objective of this study was to evaluate changes in daily activity during treatment and to compare them with clinical (symptoms, muscle strength) and biological reference measurements. We therefore equipped patients with a watch including an accelerometer and we recorded their physical activity 24 hours a day, for two weeks over six months, after the start of treatment. We measured a greatly reduced daily physical activity in all the patient, reflecting the impact of the disease on patients’ physical activity. During the 6 months of treatment, we observed a progressive increase in physical activity associated with an improvement in symptoms and in the quality of life of patients.
Which device did you use?
We used a commercially available device that provides access to the raw data of accelerometers. The signals are then analysed using software developed and used by a community of researchers, which includes Damien Bachasson. This allows us to free ourselves of commercial proprietary analysis tools that limit the interpretation and comparison of data and the use of these methods on a large scale at a reasonable cost.
The internet of things is in full development and allows to imagine new home assessment possibilities using connected objects, including actigraphs. Even though they may be limited in the interpretation of the information they provide, these devices, which are still rarely used in the field of neuromuscular diseases, can provide relevant information in addition to exams performed at the hospital. We are currently in a sort of transition between the scientific measuring device and the connected object. Assessment of physical activity will be a routine measure in the near future. Our work contributes to establishing a sound scientific basis for these measures.
Will this pilot study be extended?
Absolutely: Olivier Benveniste’s team has 30 “watches” and a cohort of 50 patients is currently evaluated using these same methods. All of the data will be available in a few months and the results will allow us to confirm these preliminary results as well as to improve our procedures and interpretations in future studies. We also intend to expand these investigations to patients with other neuromuscular diseases at the Institute of Myology, followed by other centres around the world. It should also be noted that a therapeutic trial in dermatomyositis is using a measure of daily activity by accelerometry as an exploratory endpoint.
** See the review that J.-Y. Hogrel co-authored:
Measuring Habitual Physical Activity in Neuromuscular Disorders: A Systematic Review.Jimenez-Moreno AC, Newman J, Charman SJ, Catt M, Trenell MI, Gorman GS, Hogrel JY, Lochmüller H. J Neuromuscul Dis. 2017;4(1):25-52. doi: 10.3233/JND-160195.
