Activity monitoring and patient-reported outcome measures in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients

Abstract

Introduction: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disease with no validated specific and sensitive biomarker, and no standard approved treatment. In this observational study with no intervention, participants used a Fitbit activity tracker. The aims were to explore natural symptom variation, feasibility of continuous activity monitoring, and to compare activity data with patient reported outcome measures (PROMs).

Materials and methods: In this pilot study, 27 patients with mild to severe ME/CFS, of mean age 42.3 years, used the Fitbit Charge 3 continuously for six months. Patients wore a SenseWear activity bracelet for 7 days at baseline, at 3 and 6 months. At baseline and follow-up they completed the Short Form 36 Health Survey (SF-36) and the DePaul Symptom Questionnaire-Short Form (DSQ-SF).

Results: The mean number of steps per day decreased with increasing ME/CFS severity; mild 5566, moderate 4991 and severe 1998. The day-by-day variation was mean 47% (range 25%-79%). Mean steps per day increased from the first to the second three-month period, 4341 vs 4781 steps, p = 0.022. The maximum differences in outcome measures between 4-week periods (highest vs lowest), were more evident in a group of eight patients with milder disease (baseline SF-36 PF > 50 or DSQ-SF < 55) as compared to 19 patients with higher symptom burden (SF-36 PF < 50 and DSQ-SF > 55), for SF-36 PF raw scores: 16.9 vs 3.4 points, and for steps per day: 958 versus 479 steps. The correlations between steps per day and self-reported SF-36 Physical function, SF-36 Social function, and DSQ-SF were significant. Fitbit recorded significantly higher number of steps than SenseWear. Resting heart rates were stable during six months.

Conclusion: Continuous activity registration with Fitbit Charge 3 trackers is feasible and useful in studies with ME/CFS patients to monitor steps and resting heart rate, in addition to self-reported outcome measures.

Clinical trial registration: Clinicaltrials.gov: NCT04195815.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. CONSORT flow diagram.

Flow diagram of enrollment, follow-up and analysis in the study “Activity monitoring in ME/CFS”.

Fig 2. Patient example.

Patient example with raw data for steps per 24 hours and resting heart rate, days 1–168.

Fig 3. Steps per 24 hours, by severity, by SF-36 physical function, and by combination of SF-36 physical function and DSQ-SF.

(A) Steps per 24 hours (mean, 95% CI) during follow-up, by severity categories; Mild, Moderate and Severe. (B) Steps per 24 hours (mean, 95% CI) during follow-up, by three categories based on baseline SF-36 PF. (C) Steps per 24 hours (mean, 95% CI) during follow-up, in two groups based on; SF-36 PF > 50 or DSQ-SF 55. The largest changes in mean steps between 4-week time periods, with difference highest versus lowest are indicated. General Linear Model (GLM) for repeated measures with p values for time effect and for interaction time-by-group are shown.

Fig 4. Correlations between baseline clinical data, PROMs, steps per 24 hours and resting heart rate.

Spearman’s correlation plot between baseline steps per 24 hour (mean, weeks 1–4), resting heart rate (mean, weeks 1–4), age, Body Mass Index. Short Form-36 Health Survey (SF-36); The raw scores (scale 0–100) for the six SF-36 domains (Mental health (SF36-MH), Physical function (SF-36 PF), Bodily pain (SF-36 BP), General health (SF-36 GH), Social function (SF-36 SF) and Vitality (SF-36 VF). Composite Autonomic Symptom Score-31 (COMPASS-31); sum and Compass orthostatic, DePaul Symptom Questionnaire–Short Form (DSQ-SF), and Function Level. Significant p-values are shown below Spearman’s rho, with no adjustments for multiple correlations.

Fig 5. Activity data: Resting heart rate by severity, steps per 24 hours measured with Fitbit and SenseWear.

(A) Resting heart rate, mean (min and max) levels, by three severity groups. (B) Steps per 24 hours measured for seven consecutive days by Fitbit and SenseWear, at baseline, 3 months and 6 months. (C) Bland-Altman plot showing difference (bias) between Fitbit and SenseWear devices for measured steps per 24 hours.

Fig 6. SF-36 subdomains (mean, 95% CI) during follow up; SF36 Physical Function (SF-36 PF) by severity categories, and by categories of baseline SF-36 PF.

(A) SF-36 domains during follow-up; MH: Mental Health, PF: Physical Function, BP: Bodily pain, GH: General health, SF: Social function and VT: Vitality. Raw scores, scale 0–100, lower scores denote lower function. (B) SF-36 Physical Function (mean, 95% CI) during follow up shown in separate panels, for the severity categories. (C) SF-36 Physical Function (mean, 95% CI) during follow-up by three categories based on the baseline level of SF-36 PF; 45. General Linear Model (GLM) for repeated measures with p values for time effect and for interaction time-by-group are shown.

Fig 7. DSQ-SF and SF-36 Physical Function during follow-up, by ME/CFS categorized based on a combination of baseline SF-36 PF and DSQ-SF scores.

(A) DePaul Symptom Questionnaire–Short Form (DSQ-SF) score (mean, 95% CI) during follow-up, by categories based on baseline SF-36 Physical Function; 45. (B) SF-36 Physical function score (mean, 95% CI) during follow-up, by two groups based on: SF-36 PF > 50 OR DSQ-SF 55. (C) DSQ-SF score (mean, 95% CI), by two groups based on; SF-36 Physical Function >50 OR DSQ-SF 55. The largest changes in mean scores between 4-week time periods, with difference highest versus lowest, are indicated. General Linear Model (GLM) for repeated measures with p values for time effect and for interaction time-by-group are shown.