Determinants of adherence and safety in fully autonomous home-based transcranial direct current stimulation for
Wolnei Caumo1,2,3, Lucas Bohrer Flores1, Isabela Souza Fontoura2
1Post-Graduate Program in Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
Background:
Autonomous home-based transcranial direct current stimulation (HB-tDCS) is a scalable non-pharmacological intervention for chronic pain, but evidence under fully autonomous use remains limited.
Objectives:
To identify factors associated with adherence to fully autonomous HB-tDCS; to characterize the incidence, severity, and timing of adverse events under active and sham stimulation; and to examine if patient and clinical factors, including adverse events and clinical response, are associated with variability in adherence and safety outcomes.
Design:
Secondary pooled analysis of three double blind, sham-controlled randomized clinical trials.
Subjects:
A total of 234 women with fibromyalgia diagnosed according to the 2016 American College of Rheumatology criteria.
Methods:
Participants received a standardized autonomous HB-tDCS protocol (≥20 sessions). The primary outcomes were adherence and safety. We examined associations with adherence and adverse events using generalized linear mixed-effects models, adjusted for demographic, clinical, and psychosocial factors. We also explored whether the burden of adverse events explained the link between treatment allocation and adherence.
Results:
Overall adherence was 82.6% (95% CI, 81.6-83.6). Adherence rates were similar for the active (84.7%, 95% CI, 83.3-86.0) and sham groups (80.5%, 95% CI, 78.9-82.1). Older age (β = -0.024 sessions/year; 95% CI, -0.040 to -0.008) and greater central sensitization (β = -0.025 per point; 95% CI, -0.040 to -0.010) were associated with lower adherence. Higher depressive symptom severity was linked to higher adherence (β = 0.041 per point; 95% CI, 0.040-0.060). Most participants reported no adverse events (67.0%, 95% CI, 61.0-73.0), with no group differences (χ 2 = 0.04, p = 0.83). Reported events were mostly mild and brief. Active stimulation led to more frequent tingling and erythema. Higher education (β = 0.078; 95% CI, 0.023-0.130) and depressive symptoms (β = 0.037; 95% CI, 0.020-0.050) were associated with more adverse event reports. Greater functional impairment was linked to fewer reported events (β = -0.003; 95% CI, -0.040 to -0.007).
Conclusions:
Autonomous home-based transcranial direct current stimulation was feasible, safe, and highly adhered to in fibromyalgia, with adherence and safety influenced by clinical and psychosocial factors, supporting scalable implementation in chronic pain.
