For many years, guidance around healthy sleep has centred on the number of hours spent asleep each night. However, emerging evidence suggests that for older adults, how well they sleep may be more critical for next-day thinking skills than how long they sleep. A recent study by researchers from Penn State and a medical college in the Bronx indicates that sleep quality can influence cognitive performance the following day, even when total sleep time remains unchanged.
The study, published in mid-December in the journal Sleep Health, showed that older adults who experienced more disrupted sleep processed information more slowly the next day. Rather than focusing on bedtime or total hours of sleep, the researchers assessed sleep quality by measuring how long participants remained awake after initially falling asleep. This period of wakefulness proved a stronger predictor of next-day cognitive speed than sleep duration alone.
One of the study’s authors explained that most people are familiar with the mental fog that follows a poor night’s sleep, but this research aimed to pinpoint which aspects of sleep matter most for daily cognitive functioning. The findings suggest that, at least in the short term, sleep continuity plays a key role for older adults. In other words, a night marked by frequent awakenings may impair cognition even if the overall number of hours slept appears adequate.
The researchers analysed data from 261 adults aged 70 or older who were taking part in a long-running study of ageing and cognitive health. Over 16 days, participants wore wrist-based devices that recorded their sleep patterns. During the same time, they completed brief cognitive tasks on a smartphone several times each day, including after waking and before bedtime. These tasks measured processing speed, visual working memory, and visuospatial abilities, resulting in more than 20,000 individual assessments.
On average, participants slept just over seven hours per night but spent more than an hour awake. When an individual experienced an additional half-hour of wakefulness compared with their usual pattern, their processing speed was noticeably slower the next day. Factors such as naps, bedtime, and total sleep duration did not show a meaningful association with cognitive performance. When comparing participants, those who consistently spent more time awake at night also performed worse on several cognitive tests, including measures of working memory.
Sleep disturbances are common in later life, and persistent problems have been linked to faster cognitive decline and a higher risk of dementia. The researchers emphasised that occasional poor sleep is not a cause for alarm, and that worrying about sleep can make matters worse. Instead, they advised focusing on long-term habits, such as maintaining a consistent bedtime, creating a calm sleep environment, and limiting screen use before bed. Where difficulties persist, non-drug approaches such as cognitive behavioural therapy may help improve sleep quality safely, potentially supporting healthier cognitive ageing over time.
More information: Orfeu Buxton et al, Within- and between-person associations of sleep characteristics with daily cognitive performance in a community-based sample of older adults, Sleep Health. DOI: 10.1016/j.sleh.2025.11.010
Journal information: Sleep Health Provided by Penn State
