Researchers at Duke-NUS Graduate Medical School Singapore (Duke-NUS) have found evidence that the less older adults sleep, the faster their brains age. These findings, relevant in the context of a rapidly aging society, pave the way for future work on sleep loss and its contribution to cognitive decline, including dementia.
Past research has examined the impact of sleep duration on cognitive functions in older adults. Though faster brain ventricle enlargement is a marker for cognitive decline and the development of neurodegenerative diseases such as Alzheimer’s, the effects of sleep on this marker have never been measured.
The Duke-NUS study examined the data of 66 older adults who underwent structural MRI brain scans to measure brain volume and cognitive function every two years. Sleep duration was recorded through a questionnaire. Those who slept fewer hours showed evidence of faster ventricle enlargement and decline in cognitive performance.
“Our findings relate short sleep to a marker of brain aging,” said Dr June Lo, lead author of the study. “Work done elsewhere suggests that seven hours a day for adults seems to be the sweet spot for optimal performance on computer based cognitive tests. In coming years we hope to determine what’s good for cardio-metabolic and long term brain health too,” added Professor Michael Chee, Director of the Centre for Cognitive Neuroscience at Duke-NUS. (1)
Memory and Executive Problems
In a related recent study conducted by sleep researchers at the University of Warwick, sleep problems were positively linked to declining memory and executive function in older people.
In adults between 50 and 64 years of age, short sleep (less than 6 hours per night) and long sleep (more than 8 hours per night) were associated with lower brain function scores. By contrast, in older adults (65-89 years) lower brain function scores were only observed in long sleepers.
Dr Michelle A Miller says “6 to 8 hours of sleep per night is particularly important for optimum brain function, in younger adults.”
“These results are consistent with our previous research which showed that 6 to 8 hours of sleep per night was optimal for physical health, including lowest risk of developing obesity, hypertension, diabetes, heart disease and stroke.”
Interestingly, in the younger adults, sleep quality did not have any significant association with brain function scores, whereas in the older adults (>65 years), there was a significant relationship between sleep quality and the observed scores.
“Sleep is important for good health and mental wellbeing” says Professor Francesco Cappuccio, “Optimizing sleep at an older age may help to delay the decline in brain function seen with age, or indeed may slow or prevent the rapid decline that leads to dementia.”
Dr Miller concludes that “if poor sleep is causative of future cognitive decline, non-pharmacological improvements in sleep may provide an alternative low-cost and more accessible Public Health intervention, to delay or slow the rate of cognitive decline.” (2)
1. June C. Lo, Kep Kee Loh, Hui Zheng, Sam K.Y. Sim, Michael W.L. Chee. Sleep Duration and Age-Related Changes in Brain Structure and Cognitive Performance. SLEEP, 2014; DOI: 10.5665/sleep.3832
2. Michelle A. Miller, Hayley Wright, Chen Ji, Francesco P. Cappuccio. Cross-Sectional Study of Sleep Quantity and Quality and Amnestic and Non-Amnestic Cognitive Function in an Ageing Population: The English Longitudinal Study of Ageing (ELSA). PLoS ONE, 2014; 9 (6): e100991 DOI:10.1371/journal.pone.0100991