TDCS as Augmentation Therapy to Cognitive Training in Mild Dementia

Due to increase in life expectancy, major neurocognitive disorder (MND) becoming increasingly important as reflected in the increasing number in dementia population, as well as in burden to health care system and to caregiver.

Among current treatment, cognitive training has shown to have significant outcome in cognitive impaired patient. But the effect is reported to be small and might not be long-lasting. In consideration of the neuronal excitability effect in tDCS, it may consolidate the effect of cognitive training if used simultaneously. The study will investigate on efficacy of tDCS as combined intervention to cognitive training.

The study aims to investigate the efficacy of 2-week (5 sessions per week) tDCS to augment cognitive training in subjects with major neurocognitive disorder with clinically mild severity. Patients with diagnosis of MND or dementia from HKWC will be recruited with inclusion and exclusion criteria listed. The eligible participants will be randomized to receive either active intervention (active tDCS) or sham (sham tDCS) as control with cognitive training simultaneously.

Each session lasts for 20 minutes. The subjects will be allocated to either interventional group or control group using block randomization. Block of 4 will be used to allocate subjects at 1:1 ratio between two groups. Both the participants and investigators responsible for assessment and data analysis will be blinded to the group allocation. Primary outcome and secondary outcome will be assessed at baseline, week 2 (after course of intervention) and 4 weeks after the course of intervention. Baseline assessment assesses on demographic data (e.g. age, gender, years of education), clinical data with full psychiatric assessment and access to previous medical record, neuropsychiatric data (HK-MoCA and CNPI). Primary outcomes includes N-back (cognitive training) performance, forward and backward digit span. Secondary outcomes includes measurement on dementia rating and trail making test. In data analysis, any group differences in demographics and clinical profiles between the intervention and sham group at baseline will be assess. ANOVA will be performed to examine the effect of time and intervention on primary outcome and other cognitive assessment across time points. Potential confounders will be adjusted.

Baseline assessments and outcome measures is either psychiatric assessment, clinician rating scales or cognitive assessment performed with investigator. No questionnaires will be given to participants.

Inclusion criteria

• 65 years of age or above
• Right-handedness Chinese as defined by Edinburgh handedness inventory
• Cantonese speaking
• Fulfil the criteria of Major neurocognitive disorder, as defined by the 5 th Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM- 5)
• Clinical Dementia Rating Global score = 1

Exclusion criteria

• Active diagnosis of mood disorder or psychosis
• Alcohol or substance dependence
• Initiation or change in dose of cognitive enhancer within 6 months prior to the onset of the study 14
• Poor physical condition and mobility
• Having regular cognitive training (as defined by at least three 1-hour weekly structured and standardized cognitive training in recent 3 months) 15
• Receiving tDCS within 2 months prior to the onset of study 16
• Significant communication or visual impairment
• Having metal implant in area above upper back, or having metal crown or metal brace, or pacemaker