RESUMO
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 (Mageâ¯=â¯69.69, SDâ¯=â¯8.33; Meducâ¯=â¯16.27, SDâ¯=â¯2.42) who participated in our double blind randomized controlled studies or in case studies that used HD-tDCS for 20-30â¯min at 2â¯mA (nâ¯=â¯66, 31 active) or 3â¯mA (nâ¯=â¯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 (2â¯mA and 3â¯mA) in first session (allpâ¯>â¯.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 (χ2â¯=â¯0.689, pâ¯=â¯.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 3â¯mA. These data support the use of HD-tDCS in randomized controlled trials and clinical translation efforts.