Deep sleep is important for memory consolidation, yet, as human beings enter into middle age, the quantity of deep (or slow wave) sleep they achieve is known to decrease significantly. Researchers believe that this reduction in slow wave sleep is one of the causes of memory loss when we age, and neuroscientists are constantly researching new methods to enable people to achieve better quality sleep in their older years.
A recent study, published by scientists at Northwestern University (March, 2017) has shown that a promising new way to achieve deep sleep in older adults, is gentle sound stimulation (such as the sound of waves or water flowing), synchronized to the rhythm of brain waves. The study showed that elderly adults who relied on this technology, not only achieved more deep sleep but were also able to recall more words. Previous research had shown that acoustic stimulation methods worked well with young adults in terms of increasing the quantity of deep sleep but the new study is the first of its kind to be carried out on older adults.
In the study, 13 participants between the ages of 60 and 84 received acoustic stimulation on one night, and placebo stimulation on another night. On both occasions, participants took a memory test before sleeping, and again in the morning. Those who received the placebo stimulation showed better results in the morning than they had at night time, but those who received ‘pink-noise stimulation’ using a specific algorithm, saw three times as much improvement in their test results. Memory improved in accordance with the degree of slow wave sleep stimulation provided, indicating that deep sleep is indeed important for memory retention, even for older people.
The secret of pink noise stimulation lies in the algorithm developed by one of the study authors, Giovanni Santostasi, a specialist in Neuroscience, Biotechnology and Biostatistics. This algorithm is both automated and adaptive, capable of monitoring slow wave activity in the EEG, and phase-locking the timing of the pink noise stimulation to one particular phase of the slow wave. The algorithm adapts to each individual, given that each person achieves deep sleep at a different time.
Achieving deep sleep is as vital as keeping our circadian rhythms in sync. Failing to respect the natural sleep-wake cycle can lead to everything from problems with learning to sleep disturbance and mood changes, while deep sleep is crucial for hormone regulation and physical renewal. The lead authors of the study noted that although larger studies would be necessary to confirm the efficiency of pink noise stimulation in older adults, the technology could eventually be offered to people for home use. They are currently conducting research into whether or not acoustic stimulation can improve cognitive functioning in adults with mild cognitive impairment. Previous studies carried out in these individuals showed that there is a possible relationship between quality of sleep and memory impairment.
The study authors also stated that more research would be required to elicit the effects of repeated nights of pink noise stimulation on the brain physiology and memory. The positive results achieved thus far, they noted, could indicate that the elderly population (particularly those with a high risk for cognitive decline, such as the elderly and those with cardiovascular disease) could benefit greatly form this relatively simple intervention. Future studies would therefore need to focus on repeated use at home, potentially over various weeks, as a means of improving memory in high-risk groups.
Some of the areas most affected by cognitive decline in the elderly include memory, processing speed and executive function. Elderly adults often complain that they cannot recall specific facts or episodes; this type of decline is related to age-related dementia. The researchers noted that cognitive decline is often attributed to failures in encoding and/or retrieval of information, yet consolidation also plays a vital role in optimal cognitive functioning.
Guest Author: Anne James is a freelance writer. She previously held a management role in healthcare.