Image courtesy of Stanislav Trifonov @Flickr

Although the British summer is back to rain clouds and gale-force winds, there are still plenty of other reasons to find yourself struggling with sleep. Work, money worries, British politics, or the thought of an existence without cauliflower cheese (https://www.theguardian.com/food/2019/aug/12/cauliflower-shortage-uk-extreme-weather). 

Regardless of the reason, sleep is a fundamental need for all. Even bees struggle if they don’t get sufficient shut-eye. However, as we age, our ability to stay asleep deteriorates. At the same time, we start to see health issues, such as heart problems and dementia, appear – many commonly linked to a lack of sleep. This is where a recently published study from University of Manchester researchers comes in. They wanted to know how changes in sleep precede these changes in our health as we get older.

The team led by PhD student Altug Didikoglu chose to focus their efforts on a particular facet of sleep known as sleep efficiency, or the proportion of time spent asleep in bed. As Altug highlights, “(sleep efficiency) drops non-stop with age and so we thought that it may have a specific impact on health in the elderly.”

Participants were initially recruited between 1982 and 1994 as part of the University of Manchester Longitudinal Study of Cognition in Normal Healthy Old Age, and were administered sleep, general health, and lifestyle questions up until last year. This allowed Altug and his team to not only track how sleep changed over time but also to understand how it may have impacted health later on. 

When they examined this decades-long treasure trove of data, the team found that sleep efficiency worsened as the participants aged. This is not surprising and is as we would expect. However, there are some people who, as they aged, didn’t see a dip in their ability to remain asleep throughout the night. Their sleep efficiency remained relatively intact. This group also appeared to be at a reduced risk for recurring depression, hypertension, circulatory and breathing problems in old age. Something about maintaining their sleep efficiency was protective.

So the Manchester based team decided to examine this finding further. They looked at how sleep timing (e.g. when we fall asleep and wake up) changes as we age, and how this impacts our health. By examining the same large sample they found that people who went to bed and woke up earlier tended to have a reduced mortality risk compared to the night owls (who typically slept and woke up later). This relationship remained after accounting for known health risks (e.g. smoking, drinking, and sleep duration). This suggested it was not only the proportion of time spent asleep but also when the group drifted off that was important for their health. Although multiple things influence whether you are an early bird or night owl, it suggests this element of sleep is also important for our health as we get older.

One key question that these decades long studies could not answer was why timing or efficiency of sleep was important for health. Speaking to the lead author about this he proposed some potential explanations, 

“Sleep problems disrupt homeostasis of the body. Many cognitive and metabolic systems are influenced by sleep disruption. One candidate linking sleep to health is the immune system, as disruption of the immune system by lack of sleep can lead to infections. In addition, sleep is responsible for removing toxins in the brain and lack of sleep may lead to an increase of degenerative molecules. Finally, there is a direct correlation between sleep problems in shift-workers and a variety of health problems they suffer from (e.g. cancer, depression, heart and digestive problems) and this is thought to be mediated by our internal biological clock.”

There is a clear next step for his group. They want to understand why our sleep changes as we get older by “…looking at the genes that may be behind these age-dependent changes of sleep”. A greater understanding of what causes the changes in sleep might provide some scope for altering or pre-empting these changes to improve health.

Until then, and for our health’s sake, let’s hope the dwindling cauliflower population is resolved. We evidently need fewer sleepless nights.

Jack Barton