Exercise boosts cognitive function after a bad night's sleep

Sleep is fundamental in maintaining a healthy lifestyle, with adults recommended to have between seven and nine hours a night, but recent reviews indicate that 40% of the global population don’t get enough. Now, an international study led by the University of Portsmouth has revealed that moderate-intensity exercise can improve cognitive function in people who are sleep deprived and have low levels of oxygen.

In the short term, a lack of sleep can reduce cognitive performance (CP), which takes a toll on your attention span, judgement and emotional state. The good news, according to the new study, is that CP improves during a bout of moderate-intensity exercise, regardless of a person’s sleep status or oxygen levels.

The study, published in the journal Physiology & Behavior, involved two experiments, each with 12 participants (24 in total). The first looked at the impact of partial sleep deprivation on a person’s cognitive performance and the second examined the impact of total sleep deprivation and hypoxia (low levels of oxygen). Both experiments saw participants undertake a bout of 20 minutes of cycling.

“Because we were looking at exercise as a positive intervention, we decided to use a moderate-intensity program as recommended in existing literature,” said Dr Joe Costello, from Portsmouth’s School of Sport, Health & Exercise Science (SHES).

“If the exercise was any longer or harder, it may have amplified the negative results and became a stressor itself.”

In the first experiment, individuals were only allowed five hours of sleep a night, over three days. Each morning they would be given seven tasks to perform at rest and then while cycling. They were also asked to rate their sleepiness and mood before completing the tasks.

The results showed the effects of three nights of partial sleep on executive functions were inconsistent; the paper says an explanation for this could be that some people are more resilient to a mild or moderate sleep deficit. However, regardless of sleep status, moderate-intensity exercise improved performance across all the tasks.

In the second experiment, participants went an entire night without sleep and were then put in a hypoxic environment at Portsmouth’s extreme environment laboratories. Despite oxygen levels being lowered, exercise continued to improve cognitive performance.

“One potential hypothesis for why exercise improves cognitive performance is related to the increase in cerebral blood flow and oxygenation; however, our findings suggest that even when exercise is performed in an environment with low levels of oxygen, participants were still able to perform cognitive tasks better than when at rest in the same conditions,” said co-lead author Dr Thomas Williams, from the university’s Extreme Environments Research Group. Costello added that this is the first study to suggest that exercise improves CP after both full and partial sleep deprivation, and when combined with hypoxia.

The paper says explanations for why CP improves during exercise — even when a person is sleep deprived and low on oxygen — could be changes to the amount of brain-regulating hormones, as well as a number of psychophysiological factors including cerebral blood flow, arousal and motivation. It suggests that cognitive performance is not solely dependent on the prefrontal cortex (PFC) area of the brain, despite it playing an integral role in the performance of tasks.

“The PFC is highly sensitive to its neurochemical environment and is highly susceptible to stress,” said co-lead author Juan Ignacio Badariotti, from Portsmouth’s Department of Psychology.

“It regulates our thoughts, actions and emotions and is considered to be the primary part of the brain associated with executive functions.

“But our findings suggest the mechanisms behind CP may not be isolated to this area, and instead we should consider it being the product of a series of coordinated processes widely distributed across different cortical and subcortical regions.”

The paper recommends deeper investigation to reveal what neurobiological mechanisms are behind the cognitive function process, with the authors hoping to conduct further studies with a broader mix of participants. Their work could support anyone who experiences broken sleep or low oxygen, including climbers and skiers, as well as parents of young children and shift workers.

“The findings significantly add to what we know about the relationship between exercise and these stressors, and help to reinforce the message that movement is medicine for the body and the brain,” Costello said.

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