Fitbit as an activity monitor in idiopathic inflammatory myopathy: results from a real-world cohort
Authors' conclusion
In a large IIM cohort, Fitbit® PAM variables demonstrate favourable compliance and psychometric properties with strong test-retest reliability and validity.
Study context
- Population
- IIM patients (dermatomyositis (DM), necrotising myopathy (NM), polymyositis (PM)) followed over 6 months; mean age 55.5±13.43; 75% females; 81% White51% DM, 39% PM, 9% NM
- Participants
- 120 patients
- Exposure
- Tele-Research Cohort (TRC) vs Centre-Based Cohort (CBC)
- TRCn = 82
- CBCn = 38
- Outcome
- Psychometric properties and performance of wrist-worn Fitbit (average daily steps per minute and average peak 1-minute cadence) in IIM
Methodological detailsmulticentre, observational, remote and centre-based enrolment, Functional and patient-reported outcome measures completed monthly; Fitbit worn 7 consecutive days per month
- Multicentre
- Observational
- Remote and centre-based enrolment
- Functional and patient-reported outcome measures completed monthly; Fitbit worn 7 consecutive days per month
Main finding
As reported in the abstract
Test-retest reliability of Fitbit PAM measures
Average steps/min, test-retest reliability (r; p<0.0001)
0.89
Average peak 1-minute cadence, test-retest reliability (r; p= 0.0001)
0.86
Observational data: associations, not effects.
Further findings
Associations of demographics and disease subtype with physical activity monitors (PAM) measures
- Gender, race/ethnicity or disease subtypes not associated with PAM measures
- TRC and CBC similar in demographics and disease subtypes
Original publication
Fitbit as an activity monitor in idiopathic inflammatory myopathy: results from a real-world cohort. Clin Exp Rheumatol. Published 24 February 2026. doi:10.
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