The Effect of Transcranial Direct Current Stimulation Upon Sleep Spindles in Healthy Older Adults: a Pilot Randomised Controlled Study

A good quantity, and quality, of sleep is crucial for well-being. Evidence strongly indicates that poor sleep quality and quantity is causally involved in the development of dementia; therefore, techniques which can improve sleep in older adults are very likely to prevent or slow down the disease process in dementia.

This project aims to manipulate a specific aspect of sleep in healthy older adults. This: 1) has the potential to prevent the pre-dementia stage of mild cognitive impairment in healthy older adults, and 2) has a direct clinical application to dementia. The overall aim of this project is to investigate if a non-invasive brain stimulation technique called transcranial direct current stimulation (tDCS) can enhance specific brain activity patterns during overnight sleep in healthy older adults.

These brain activity patterns during sleep (called 'sleep spindles') are mechanistically linked to both the physiological restorative and the cognitive function of sleep. Sleep spindles can only be assessed by measuring overnight brain activity during sleep. Sleep spindles are very strongly associated with attention, and memory performance, which are severely affected by dementia. A decrease in sleep spindles is associated with cognitive decline, and predict dementia development. Therefore, enhancing sleep spindle activity in sleep is likely to boost cognition.

Whilst previous research studies have demonstrated that in a sleep laboratory environment, tDCS can manipulate sleep spindles when individuals are in a specific brain state in a nap situation, we are specifically interested in testing tDCS in a home environment. This is because the use of tDCS in a home environment has have a number of advantages over sleep laboratory studies. Specifically, by conducting this study in a home environment, this will maximise the inclusivity of studies involving older adults, and DLB patients, since they will not be required to travel to a sleep laboratory to participate in studies.

The aim of this proof-of-principle study is to investigate if tDCS can manipulate sleep spindles in healthy older adults. It is expected that relative to a placebo stimulation, active stimulation (which exerts an effect upon the brain) will increase sleep spindle activity in healthy older adults.