Tolerability and blinding of 4x1 high-definition transcranial direct current stimulation (HD-tDCS) at two and three milliamps

Brain Stimul. 2018 Sep-Oct;11(5):991-997. doi: 10.1016/j.brs.2018.04.022. Epub 2018 May 4.

Abstract

Background: Transcranial direct current stimulation (tDCS) is an in-demand form of neuromodulation generally regarded as safe and well tolerated. However, few studies have examined the safety, tolerability, or blinding of High Definition (HD-) tDCS, especially in older adults and at stimulation intensities of 2 milliamps (mA) or greater.

Objective: We examined the rates of serious adverse events and common side effects to establish safety and tolerability, respectively, in HD-tDCS. Blinding was evaluated using participants' accuracy in correctly stating their condition (i.e., active or sham).

Methods: The sample included 101 older adults (Mage = 69.69, SD = 8.33; Meduc = 16.27, SD = 2.42) who participated in our double blind randomized controlled studies or in case studies that used HD-tDCS for 20-30 min at 2 mA (n = 66, 31 active) or 3 mA (n = 35, 20 active). Participants completed a standardized side effect questionnaire and were asked whether they received active or sham stimulation at the end of each session.

Results: There were no serious adverse events and no participants withdrew, suggesting that HD-tDCS meets basic safety parameters. Tolerability was comparable between active and sham HD-tDCS regardless of intensity (2 mA and 3 mA) in first session (allp > .09). Tingling was the most commonly endorsed item (59% active; 56% sham) followed by burning sensation (51% active; 50% sham), the majority of which were mild in nature. "Severe" ratings were reported in fewer than 4% of sessions. Blinding appeared adequate since there were no significant group differences between individuals correctly stating their stimulation condition (χ2 = 0.689, p = .679). The above tolerability and blinding findings generally persisted when multiple session data (i.e., 186 total sessions) were considered.

Conclusions: HD-tDCS appears well-tolerated and safe with effective sham-control in older adults, even at 3 mA. These data support the use of HD-tDCS in randomized controlled trials and clinical translation efforts.

Keywords: Adverse events; HD-tDCS; Safety; Sham.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Aphasia, Primary Progressive / psychology
  • Aphasia, Primary Progressive / therapy
  • Cognitive Dysfunction / psychology
  • Cognitive Dysfunction / therapy
  • Double-Blind Method
  • Female
  • Headache / diagnosis
  • Headache / etiology
  • Humans
  • Leukoencephalopathies / psychology
  • Leukoencephalopathies / therapy
  • Male
  • Middle Aged
  • Pain / diagnosis
  • Pain / etiology
  • Stress Disorders, Post-Traumatic / psychology
  • Stress Disorders, Post-Traumatic / therapy
  • Surveys and Questionnaires
  • Transcranial Direct Current Stimulation / adverse effects*
  • Transcranial Direct Current Stimulation / methods*