Physical activity monitors, such as the accelerometer device ActivPal, can provide a unique perspective on the impact of sarcoidosis on patients’ function not captured by current clinical outcome measures, researchers suggest.
Studies have demonstrated that dyspnea (breathlessness), fatigue, and joint pain can have a severe impact on physical activity in sarcoidosis. Although those studies have used reliable, well-defined approaches such as the six-minute walk test (6MWT) or cardiopulmonary exercise tests to assess patient activity, these tools hold some limitations.
Also, studies using regular activity measurements, such as steps per day to correlate exercise capacity with clinical outcomes, often fail to include a healthy control for comparison. So there is still limited understanding of how the disease affects a patient’s daily physical activities.
To fill this knowledge gap, researchers conducted a pilot study in which people with pulmonary sarcoidosis and healthy volunteers used a device called a piezoelectric triaxial accelerometer to appraise physical activity. ActivPal is a device that can be worn daily and measures a range of physical activities.
Researchers also compared the accelerometer’s collected data with participants’ outcome measured by 6MWT, lung function tests, fatigue levels, and health status, among other clinical parameters.
The study enrolled 15 participants (mean age 52.7) with pulmonary sarcoidosis from a secondary care specialist clinic at King’s College Hospital, and 14 healthy age-, sex-, and weight-matched volunteers.
All participants used the ActivPal device attached to their upper thighs for over one week, and were asked to respond to four questionnaires in which they reported their patterns of physical activity, fatigue, dyspnea, and global health status.
Through ActivPal data, researchers found that both daily step numbers and stepping times were significantly lower in participants with sarcoidosis (mean 5,624 steps and 1.18 hours per day, respectively) compared with healthy controls (mean 10,429 steps and 1.97 hours per day).
Sarcoidosis patients also showed reduced exercise capacity, with just 375 meters (0.23 miles) covered in the 6MWT compared with 487 meters (0.30 miles) of the control group. Further analysis showed a significant association between 6MWT and the number of daily steps determined by ActivPal.
Vigorous physical activity was also found to be reduced among sarcoidosis patients compared with healthy participants. Only two (13%) participants with sarcoidosis had undertaken vigorous activity during the last seven days, compared with seven (50%) healthy controls. Of note, vigorous exercise reports also correlated with 6MWT distances.
Self-reports revealed that the sarcoidosis group had on average more fatigue than the control group, which was also linked to the reduced time measured by ActivPal that the patients spent upright or standing per day.
In general, patients who had better lung-specific health were found to spend more time standing or upright per day, while those with worse dyspnea scores were the ones who had a reduced number of sit-to-stand transitions assessed by the accelerometer. Lung health scores also correlated significantly with self-reported overall physical activity.
“Physical activity monitors can provide a unique assessment of the impact of disease on function that is not captured by existing clinical outcome measures for sarcoidosis, and can potentially be used to assess response to therapy,” researchers said.
“The mechanism for reduced physical activity in sarcoidosis is unclear but is likely to be multi-factorial and needs further study,” they concluded.