In what ways does sleep affect memory?

But, how does this happen? Dr Dey explained that the sleep cycle of a healthy adult has distinct phases — NREM (non-rapid eye movement) and REM (rapid eye movement). Further, NREM sleep has N1, N2, and N3 or slow wave sleep (SWS). “Slow wave sleep is deep sleep and is very important as biochemical restorative activities take place during this phase. This phase comprises 20-25 per cent of our total sleep time. This phase of sleep also supports the processing of new information and its subsequent consolidation in the form of memory. In other words, the brain organises the memories from the previous day during these NREM phases, eliminating the inconsequential ones and only retaining vital information,” he said.

He further shared that sleep disorders, such as sleep apnea, cause fragmented sleep that disrupts the sleep cycle and restricts the individual from entering the N3 or SWS for an adequate amount of time, leading to impairment in biochemical restorative function and memory. “In addition, during the REM phase, we tend to dream and consolidate our memory. Retrieval or recall is an important component of our memory and REM sleep helps in adequate retrieval of memory. So, any impact during the SWS phase and REM phase may impair our memory and cognition,” Dr Dey said.

Sleep deprivation can significantly affect your memory (Source: Getty Images/Thinkstock)

Agreeing, Dr Krishnan PR, Senior Consultant, Neurology, Fortis Hospital, Bannerghatta Road, Bangalore emphasised that sleep promotes the consolidation of experiences and ideas. “Poor sleep impairs memory consolidation by disturbing the normal process in the hippocampus (a part of the brain) that draws on both NREM and REM sleep for building and retaining memories,” he said, adding that nerve connections that make our memories are strengthened during sleep, especially during NREM sleep.

But, it’s also crucial to understand that there are two types of memories – short-term and long-term. “Lack of sleep mainly affects the immediate or the short-term memory. Sleep deprivation for a long time, however, may even affect long-term memory,” Dr Kalyani Dilip Karkare, Consultant, Neurologist and Epileptologist, Manipal Hospital, Millers Road, Bangalore said, adding that lack of sleep affects our brain health in several other ways, too.

*Impaired brain activity: Lack of concentration, slowed down reaction time or logical thinking, inability to follow instructions, and difficulty absorbing new information.

*Problems with motor coordination: Increased risk of accidents while driving.

*Behavioural and personality changes: Easy irritability, anger outbursts, dysregulated emotional response.

Dr Dey concurred and said that lack of sleep affects our memory, creative thinking, problem-solving, processing of emotions, and judgement. “The brain struggles to function effectively without enough sleep. Enhancing sleep quality can help people think more clearly, perform better cognitively, and may even slow down cognitive ageing,” he said.

Does the converse stand true, too? Yes, experts said. Explaining, Dr Dey said, “Impaired memory is related to several neurological disorders. Common ones are age-related, dementia-related disorders like Alzheimer’s disease, Parkinson’s disease, neurodegenerative diseases like multiple sclerosis and stroke. All these disorders have physical as well as neurological symptoms. Additionally, sleep breathing disorders like sleep apnea also is related to depression, stroke, Alzheimer’s disease. So, the phenomenon is vice versa and may be part of the same spectrum.”

Sleep disorders can affect your health, including memory, in many ways (Source: Getty Images)

Now that the link between the two is established, let’s understand how you can ensure better sleep to prevent any harmful effects on your memory, as per the expert.

*Taking a nap: Sleeping on newly acquired knowledge is the greatest method to retain it. This is so that memories that have been established throughout the day can be strengthened while sleeping. Making connections between new and old memories also takes place.

*Staying physically active: Physical activity enhances blood flow to the entire body, including the brain. This may help to keep your memory sharp. Try a few 10-minute walks spread throughout the day if you don’t have time for a full workout.

*Maintain sound sleeping routines: Cognitive decline has been related to insufficient sleep as well as sleep that is agitated or frequently interrupted. Give priority to acquiring sufficient restful sleep. Adults should consistently get between 7 and 9 hours of sleep each night. Make an appointment to see your healthcare professional if snoring is keeping you up at night. Snoring may indicate a sleep condition like sleep apnea.

*Reduce screen time before bed: For at least an hour before bed, stay clear of all screens. The blue light emitted by electronics such as televisions, tablets, phones, and computers promotes wakefulness while suppressing hormones that promote sleep, such as melatonin.

*Practise self-care: Stress may trigger forgetfulness, which makes it important to establish expectations and boundaries in your life. One ought to additionally establish a healthy work-life balance. Taking time to unwind throughout the day can enhance cognitive functioning.

Dr Karkare added that repeating things in sequences, keeping the brain active by doing brain-boosting activities such as playing crossword, sudoku, etc, and paying complete attention and involvement in the task at hand are other ways to improve your memory, apart from practising healthy sleep hygiene.

(Next in the series: Why mouth breathing during sleep is harmful to health)

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