Relationship between clinical status and physical activity in patients suffering from inflammatory myopathies – Interview with O. Landon-Cardinal and D. Bachasson

Océane Landon-Cardinal, MD*, and Damien Bachasson, PhD** are co-first authors of an article published in Seminars in Arthritis and Rheumatism. The article relates to the relationship between clinical status (symptom severity) and physical activity in patients with inflammatory myopathies (or idiopathic myositis).

What are the origins/overall context of this project?

Myositis is a heterogeneous group of muscular diseases. In this family of diseases, the muscles degenerate rapidly and patients feel tired, weak and can very quickly find themselves disabled. Treatment generally allows them to recover almost complete muscle function.
The clinical assessment of patients with myositis, and the planning of clinical trials for these rare and heterogeneous diseases, remain difficult. Improving the management of these patients requires access to reliable measurements of disease activity that take into account the impact of the disease on patient quality of life. Access to new measurement tools should improve how treatment efficacy in clinical trials is assessed.
The International Myositis Assessment & Clinical Studies Group (IMACS) has developed measurement tools to assess muscular and extra-muscular activity in myositis. These measurement tools have been endorsed by the American College of Rheumatology/European League against Rheumatism (ACR/EULAR) in developing clinical response criteria, in order to conduct therapeutic clinical trials. However, the clinical significance of the changes measured by these tools in the daily lives of patients with myositis, in particular physical activity, have still to be clarified.

What are the objectives of this study?

Muscle weakness can cause a deterioration in the functional abilities of patients and can have a direct impact on daily physical activity (PA) undertaken by patients. By PA, we mean any movement produced that is responsible for an increase in energy expenditure during daily life. The level of daily activity reflects, inter alia, the ability of a patient to move. There are currently different ways to evaluate the daily PA of patients in their homes, such as questionnaires and, more recently, portable devices (containing accelerometers, for example) that can be worn on one’s ankle, belt or wrist, and that can provide an objective measurement of daily PA.
For our study, we used a commercial device that allows us to access the raw data from accelerometers carried on the patient’s wrist. The raw signals were then analysed using an open source software package used by an international community of researchers.
The objective of this study was to evaluate changes in daily physical activity during the course of treatment, and to compare these with the reference clinical and laboratory measurement tools (IMACS) and clinical response criteria developed by the ACR/EULAR for clinical trials.

Which methods and protocols were used?
The study was conducted at the French National Reference Centre for Neuromuscular Diseases (Pitié-Salpêtrière University Hospital, Institute of Myology) between 2017 and 2018. Patients with myositis were assessed every 3 months, then we recorded their physical activity (PA) using a wrist accelerometer 24 hours a day for two weeks after each clinical assessment.
Fifty-five patients were enrolled in this study, and they showed excellent compliance in carrying the wrist accelerometer. Our measurements showed that daily PA was significantly reduced among patients with myositis, demonstrating the negative impact of the disease on PA. Furthermore, muscle strength and physical function were major determinants of PA at enrolment and follow-up. However, changes in PA were also strongly influenced by changes in patient well-being, including depressive symptoms and level of fatigue.
In other words, our data suggest that mood disorders and fatigue must be assessed and managed in all patients, especially if there is an improvement in muscle strength without a corresponding increase in physical activity levels.

What results have been obtained?

The ability to objectively measure physical activity makes it possible to estimate the impact of a disease on the lives of patients and to measure its progression over time. So, the accelerometer is a very useful tool in assessing the efficacy of an intervention aimed at increasing the PA of patients in order to protect them, for example, from complications associated with a sedentary lifestyle.
Only patients presenting major improvement according to the ACR/EULAR score showed a significant change in PA. According to this same score, a slight to moderate improvement resulted only inconsistently in a change in PA.
Our data suggest that an increase in PA beyond a certain threshold (ENMO > 4.10 mg/day) is a simple, accessible and useful measurement to define a significant change in PA, in order to improve the quality of life of patients with myositis.

What conclusions can be drawn and what opportunities has this study opened up?

Measuring physical activity using an accelerometer may provide relevant information that is complementary to hospital examinations, and our work is helping to establish a solid scientific basis for this measuring process.
The use of accelerometers in therapeutic clinical trials should still be valued as an additional exploratory endpoint to better assess the effect of therapeutic interventions, and therefore to improve the management of these patients.


* Océane Landon-Cardinal, MD, rhumatologist. This work was carried out during her post-doctoral training in autoimmune myopathies at Pitié-Salpêtrière under the supervision of Pr Olivier Benveniste.


** Damien Bachasson, PhD**, Physiotherapist, Scientific Research Project Manager, work in the Neuromuscular Physiology Laboratory headed by Jean-Yves Hogrel.


Relationship between change in physical activity and in clinical status in patients with idiopathic inflammatory myopathy: A prospective cohort study, Océane Landon-Cardinal, Damien Bachasson, Perrine Guillaume-Jugnot, Mathieu Vautier, Nicolas Champtiaux, Baptiste Hervier, Aude Rigolet, Rohit Aggarwal, Olivier Benveniste, Jean-Yves Hogrel, Yves Allenbach, Seminars in Arthritis and Rheumatism, Volume 50, Issue 5, October 2020, 1140-1149.