Warning to bad sleepers in new study

Sleeping less than six hours a night reduces the brain benefit that comes from exercise, a study suggests.

It is already known that regular exercise can protect against memory and thinking decline as we age.

But this protective effect may be diminished for people who don’t close their eyes enough, researchers warn.

A team from University College London (UCL) studied cognitive function over 10 years in 8,958 people aged 50 and over in England.

This was assessed by a memory test, where participants were asked to recall a list of 10 words immediately and with delay, and also a verbal fluency test, where participants were asked to name as many animals as possible in one minute.

Analysis revealed that people who were more physically active but slept for less than six hours on average had faster cognitive decline overall

The researchers investigated how different combinations of sleep and exercise habits can affect people’s memory and thinking ability over time.

Analysis revealed that people who were more physically active but slept for a short time — less than six hours on average — generally had faster cognitive decline.

After 10 years, the memory and thinking skills of people in this group were the same as their peers who were less physically active but slept longer.

Lead author Dr Mikaela Bloomberg, from the UCL Institute of Epidemiology & Health Care, said: ‘Our study suggests that we may need adequate sleep to reap the full cognitive benefits of physical activity.

“It shows how important it is to consider sleep and physical activity together when thinking about cognitive health.”

At the start of the study, those who were more physically active had better cognitive function, regardless of how long they slept.

But over the course of the 10-year study period, those who slept less than six hours experienced faster cognitive decline compared to those who slept between six and eight hours.

The rapid decline was true for the over-50s and over-60s in this group, but older participants age 70 and older seemed to retain the cognitive benefits of exercise despite short sleep.

Co-author Professor Andrew Steptoe said: ‘It is important to identify the factors that may protect cognitive function in middle age and later in life as they may serve to extend our cognitively healthy years and, for some people, have a delay diagnosis of dementia.

“The World Health Organization already identifies physical activity as a way to maintain cognitive function, but interventions should also consider sleep habits to maximize long-term benefits to cognitive health.”

The findings were published in the journal Lancet Healthy Longevity.