Sleep deprivation benefited our ancestors, yet harms us now — but staying fit may help us cope

• However, we often sleep less than we need.
• Needing less sleep is a consequence of our ancestors’ choices to remain awake longer — a behaviour that led to evolutionary benefits.

Less sleep needed: An ancestral gift

• Humans are outliers, however, needing sleep for only seven hours, far less than the predicted 9.55 hours of sleep for a primate with similar traits to ours.
• This ancestral choice to sleep less was worthwhile (although some speculate that it may also have had drawbacks).

Less sleep available: A modern misery

• We forgo sleep to pull an all-nighter in preparation for an exam or a meeting, binge-watch TV shows, conform to the sleeplessness trend of the modern culture or scroll through social media.
• Sleep is not a luxury for people who must face sleep disorders, socioeconomic sleep disparity, new parenthood or work obligations of pilots, health-care workers and others with irregular hours.
• Today it is the lack of sleep that is costly because sleep is essential.
• Sleep research pioneer Allan Rechtschaffen noted, “If sleep doesn’t serve an absolutely vital function, it is the biggest mistake the evolutionary process has ever made.”

Countermeasures against sleep deprivation

• Today, getting even an hour or two of extra sleep is challenging.
• But until policies change, how can we better cope with sleep loss?

Protective power of fitness

• Fitness was measured as the ability of the participants’ heart and lungs to supply oxygen and their muscles’ ability to use it while exercising.
• This is referred to as cardiorespiratory fitness, as opposed to muscular fitness.
• A higher VO₂peak indicates better fitness.
• Research has shown that people with higher cardiorespiratory fitness tend to have better brain connectivity and cognition.

Exercise caution

• Other healthy habits of fitter participants such as good sleep hygiene, higher cognitive reserve and healthy diet may have contributed to their better memory performance despite sleep loss.
• However, animal research has shown that aerobic exercise training — which increases cardiorespiratory fitness — can protect against the detriments of sleep deprivation.