An interventional study of Placebo Transcranial Direct Current Stimulation (tDCS) and Active Transcranial Direct Current Stimulation (tDCS) in Sleep, Cognition and Healthy Aging, sponsored by Northumbria University. Completed at 1 site in United Kingdom. Open to participants aged 60 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-07.
Sponsored by Northumbria University · Not applicable, Interventional, and Prevention
The goal of this interventional study is to learn if transcranial direct current stimulation (tDCS), a gentle, cost-effective and non-invasive brain stimulation technique can improve sleep brain activity during an afternoon nap. Since these sleep brain patterns are linked to better memory, attention, and thinking skills, this study aims to find out if improving sleep in a nap can also enhance these cognitive skills in healthy older adults (aged 60+).
The main questions it aims to answer are:
Participants will:
During each session they will:
Complete an easy-to-use sleep test at home on the nights after the naps.
By taking part, participants will help researchers understand whether tDCS can improve sleep during naps and, in turn, support memory and thinking skills. This research could lead to better treatments for sleep problems, help protect brain health, and reduce the risk of dementia as people age. The brain stimulation in this study may also help improve their sleep and cognition.
Sleep is vital for maintaining physical and cognitive health across the lifespan. However, normal age-related changes to sleep can impair memory, learning, and waste clearance in the brain, contributing to the risk of cognitive decline and dementia.
Transcranial direct current stimulation (tDCS), a non-invasive technique that modulates brain activity, shows promise for enhancing both sleep and cognition. However, existing studies have significant methodological limitations. Notably, very few have investigated 'offline' tDCS -where stimulation is applied before sleep- to assess objective sleep changes using polysomnography (PSG). Instead, most research has relied on subjective measures, consistently finding that offline tDCS enhances perceived sleep quality, especially with repeated stimulation sessions. Importantly, offline tDCS may be more feasible for use outside laboratory settings compared to 'online' approaches, where stimulation is applied during sleep, making it a more scalable intervention.
Furthermore, delivering tDCS before a daytime nap, rather than nocturnal sleep, offers additional advantages by reducing participant burden, particularly in older adults. Studies applying tDCS during a nap in older adults have shown improvements in objective sleep microstructure and declarative memory. By contrast, studies applying tDCS during nocturnal sleep have reported inconsistent results. Despite its potential benefits, no studies have explored the effects of an offline, nap-based tDCS approach on objective sleep outcomes.
Additionally, few studies have examined whether repeated sessions of offline tDCS might amplify its effects on objective PSG-measured sleep. While repeated sessions have been shown to positively influence subjective sleep outcomes, it remains unclear whether the same benefits apply to objective sleep metrics. This study will address this gap by investigating whether two sessions of offline tDCS, compared to one, are necessary to improve objective sleep outcomes.
In summary, this study aims to determine whether offline tDCS applied prior to a nap can enhance objective sleep during a daytime nap and improve post-nap cognitive performance in older adults. If effective, this low-burden, non-invasive intervention could serve as a practical tool for promoting healthy aging and reducing dementia risk.
The primary objectives of this randomised, placebo-controlled crossover trial are:
To evaluate the impact of offline tDCS on objective sleep microstructure and architecture during naps.
To assess the effects of tDCS on post-nap cognitive performance. To examine the cumulative effect of two tDCS sessions upon objective sleep and cognition, compared to one.
Northumbria University is the lead sponsor of 156 studies on the registry; 22 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Transcranial direct current stimulation. Participants will experience a 20-minute session of active tDCS (1.2 mA) on two consecutive days.
Device: Active Transcranial Direct Current Stimulation (tDCS)
Transcranial direct current stimulation. Participants will experience a 20-minute session of placebo tDCS on two consecutive days.
Device: Placebo Transcranial Direct Current Stimulation (tDCS)
Placebo Transcranial direct current stimulation (tDCS): Participants will experience a 20-minute session of placebo tDCS on two consecutive days.
Also known as: sham tDCS
Active transcranial direct current stimulation (tDCS). Participants will experience a 20-minute session of active tDCS (1.2 mA) on two consecutive days.
Also known as: tDCS
Sleep spindle density
PSG-measured slow (11.99 - 12.99Hz) and fast (13 - 14.99Hz) sleep spindle density
Time frame: During nap immediately after tDCS application
Sleep spindle amplitude
PSG-measured slow (11.99 - 12.99Hz) and fast (13 - 14.99Hz) sleep spindle amplitude
Time frame: During nap immediately after tDCS application
Slow wave sleep amplitude
PSG-measured SWS amplitude (peak-to-peak, μV)
Time frame: During nap immediately after tDCS application
Slow wave sleep density
PSG-measured slow wave sleep density (number of slow waves divided by the minutes of sleep)
Time frame: During nap immediately after tDCS application
Verbal declarative memory
Change in Verbal Paired Associates Word Learning Task performance will be measured by % correct recall at baseline (before the tDCS intervention and nap) compared to % correct recall 15 minutes after the nap has taken place.
Time frame: Baseline (before tDCS/nap) and 15 minutes after the nap
Attentional Network Task (ANT)
Change in Attentional Network Task performance will be measured by Reaction Time (RT) (Milliseconds (ms) at baseline (before the tDCS intervention and nap) compared to RT (ms) 15 minutes after the nap has taken place.
Time frame: Baseline (before tDCS/nap) and 15 minutes after the nap
Attentional Network Task (ANT)
Change in Attentional Network Task performance will be measured by Accuracy (%) at baseline (before the tDCS intervention and nap) compared to Accuracy (%) 15 minutes after the nap has taken place.
Time frame: Baseline (before tDCS/nap) and 15 minutes after the nap
Visuo-spatial declarative picture memory
Change in Picture Memory performance will be measured by Accuracy (% Correct) at baseline (before the tDCS intervention and nap) compared to Accuracy (% Correct) 15 minutes after the nap has taken place.
Time frame: Baseline (before tDCS/nap) and 15 minutes after the nap
Visuo-spatial declarative location memory
Change in Location Memory performance will be measured by Accuracy (% Correct) at baseline (before the tDCS intervention and nap) compared to Accuracy (% Correct) 15 minutes after the nap has taken place
Time frame: Baseline (before tDCS/nap) and 15 minutes after the nap
Plan to share: No
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