We spend an average of 3,000 hours in dreamland every year, or in other words, a third of our lives between duvet covers and pillows, and for good reason. Sleep is related to a variety of cognitive and physiological processes in the body, and not getting enough (or sometimes even too much) sleep can have unintended health consequences.
As we age, we may also experience changes in our sleep patterns, and knowing how much sleep is optimal for healthy functioning becomes important. In a report in the Journal Nature Aging, scientists from Cambridge and Fudan University may have found an answer.
Examining data from the UK BioBank, the researchers looked at 498,277 participants between the ages of 38 and 73 who completed surveys about their sleep pattern and duration, mental health and general well-being. Of this group, 40,000 participants had brain imaging profiles and additional genetic data available for analysis.
The results of the study suggest that participants who slept approximately 7 hours per day without a major interruption in their daily sleep patterns for prolonged periods had better cognitive performance and better long-term mental health and general well-being.
Getting less or more sleep seemed to be associated with poor cognitive performance on tasks such as memory and problem-solving skills, and mental health in the participants.
The authors also found a relationship between the amount of sleep and changes in the volume of key brain regions involved in memory, such as the hippocampus, and other areas involved in cognitive processing in some participants. They speculate that changes in brain volume and other genetic mechanisms might underlie underlying changes in cognition and mental health during those who had different sleep duration.
“Although we can’t conclusively say that sleeping too much or too little causes cognitive problems, our analysis looking at people over a longer period of time seems to support this idea. But the reasons older people sleep less appear to be complex, influenced by a combination of our genetic makeup and the structure of our brains.” Professor Jianfeng Feng of Fudan University said in a statement.
The authors hint at a possible explanation for why sleep deprivation as we age could lead to cognitive decline, explaining that it could be due to slow-wave sleep disruption, which has previously been linked to dementia and memory difficulties. . Although the current study doesn’t speculate why sleeping too much might be a bad thing, previous studies have shown that sleeping too much could also lead to cognitive decline.
A certain strength of the current study is the large sample size that was used and therefore the results could be considered robust. However, the authors highlight some limitations. The surveys were self-reported, which may introduce some bias, and only asked questions about total sleep duration in participants and did not look at other aspects, such as sleep hygiene practices.
Future studies could certainly delve into these findings, but for now, we can say that as we age, 7 hours of naps every night seem to be optimal when it comes to our napping practices.
“Getting a good night’s sleep is important at all stages of life, but especially as we age. Finding ways to improve older people’s sleep could be crucial in helping them maintain good mental health and well-being and stave off cognitive decline, particularly for patients with psychiatric disorders and dementias.” Professor Barbara Sahakian from the University of Cambridge Department of Psychiatry concludes.