Sleep Duration and Quality: Cause of Cognitive Impairment in Older Adults

By: Swati Kumar, MD, Research Coordinator, Rutgers Institute for Health

Sleep disturbances and cognitive impairment are common in older adults. As people age, changes occur in sleep patterns such as a decrease in total sleep duration and efficiency, increase in sleep fragmentation, and difficulty falling asleep, along with decreased time in rapid eye movement (REM) sleep and slow wave sleep.

Studies suggest a direct connection between reduced sleep quality and worse cognitive outcomes. Studies showed that those who reported sleep disturbances were about two to four times more likely to develop a cognitive impairment than those who did not. More than a third of adults report regularly having a shorter or longer sleep duration than the typical duration of 7–9 h of sleep per day. Several prospective studies have also shown a greater risk of cognitive impairment and dementia for long and short sleep duration, and for changes in sleep duration over the lifetime.  As an example, in older adults (≥70 years) in a population-based study, an increase in sleep duration from 7–8 h to 9 h or more over 9 years was associated with a greater prevalence of cognitive impairment.

Sleep is required for the consolidation of memory and normal brain functioning, and sleep disturbance could interfere with the function of neuronal pathways. Poor sleep might contribute to neurodegeneration by promoting neuroinflammation and disrupting neurogenesis. There are many benefits to older people having a well-regulated sleeping routine; it can improve both overall health and quality of life. At its most basic level, sleep helps maintain cognitive functioning by serving as the brain’s “housekeeper” and facilitating the daily removal of metabolic waste.

Although underlying mechanism is still poorly understood, sleep disturbances might contribute to cognitive impairment through several pathways. Some promise has been shown for short-term trials of exercise and for some drugs. Due to high prevalence of sleep disturbances and cognitive disorders in older adults, the association between sleep and cognitive ageing is an important public health implication for targeting people at risk of cognitive decline.