Clinical Efficacy and Mechanism of High Definition tDCS Based on dmPFC in the Intervention of Chronic Insomnia

Fifty patients with chronic insomnia disorder diagnosed by the Diagnostic Criteria and Treatment Guidelines for Adult Insomnia (2017) were recruited from the first affiliated Hospital of Anhui Medical University. After meeting the inclusion criteria and obtaining informed consent, each participant will complete the subjective measures consisting of sleep questionnaires, polysomnography (PSG) and tDCS treatment conducted by trained researchers at the Neurology Department of Anhui Medical University. All the participants were randomized (1:1) to receive "active" or "sham" treatment protocol. The anode electrode was placed on the DMPFC (Fz) surrounded by four cathodes with a 1cm diameter (FPz, F3, Cz, and F4). Each participant received 30 min of tDCS stimulation once daily for 10 consecutive days. The stimulation direct current magnitude was set at 2 mA in the active group. In the sham intervention phase, the sensation was simulated by applying a 30s rising current until 2 mA was reached, with a 30s immediate decline at the beginning and end of each phase.

At the beginning and after a 10-day intervention, subjective measures consisting of sleep questionnaires, including the Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI), were assessed. The Flinders Fatigue Scale (FFS) and the Epworth Sleepiness Scale (ESS) were used to assess daytime sleepiness. Additionally, the HAMA and HAMD were used synchronously for emotional assessment. Afterwards, they were unblinded by the study coordinator.

Inclusion criteria

• age between 15 and 65 years,
• diagnosed with chronic insomnia based on the Diagnostic Criteria and Treatment Guidelines for Adult Insomnia (2017),
• no previous application of any insomnia pharmacological therapy for at least one week before baseline visit.

Exclusion criteria

• diagnosis of other sleep disorders, such as sleep apnoea-hypopnoea syndrome, REM behaviour disorder, and restless legs syndrome,
• history of head trauma or presence of serious organic diseases,
• presence of comorbid anxiety or depression, as assessed by a Hamilton Anxiety Scale [HAMA] score of 17 or Hamilton Depression Scale [HAMD] score of 14.