Sleep Extension Improves Health and Performance

Many of us go to great lengths to improve our health, enhance our athletic performance, and sharpen our minds. These pursuits often entail considerable effort and expense. But what if there was an easier, free way to fulfill these desires? What if we could use something as simple as sleep extension (getting more sleep than usual by allowing more time in bed) to feel and function better?

Humans are possibly the only species that voluntarily restricts its sleep, and few processes and behaviors are immune to the perils of insufficient sleep (1). Unfortunately, we all invariably lose sleep now and then, so is there anything we can do to repay our sleep debts?

Research on sleep extension is nascent. However, the results of sleep extension studies have been remarkably promising, so in this first blog we’ll explore recent findings showing that prolonging sleep may improve metabolic health, dietary choices, cognitive function, and even athletic performance. Then, in the next blog we’ll consider how you can put this knowledge to use by incorporating a few simple behaviors into your daily health practice. Let’s dive in.

Getting More Sleep Enhances Metabolic Health

To exemplify the beneficial effects of sleep extension on metabolism, we’ll focus on insulin sensitivity, a key determinant of risk of diseases like type-two diabetes. As the only hormone that lowers blood glucose, how sensitive our bodies’ tissues are to insulin influences how likely we are to experience the chronic high blood sugar (hyperglycemia) that is characteristic of diabetes.

In a study of young men and women who regularly restricted their sleep, participants were asked to prolong their sleep by one hour each night for six weeks (2). As is true of all of the studies I’ll discuss, participants successfully prolonged their sleep. The most important finding was that increases in sleep duration were associated with improvements in an index of insulin sensitivity – larger increases in sleep duration were related to greater improvements in insulin sensitivity.

These results are consistent with research on the effects of short-term sleep extension in men who regularly restricted their sleep from Monday to Friday (3). In this study, participants visited the lab on three Friday mornings. Participants then slept in the lab for three nights at each visit. At one visit, participants were allowed just six hours in bed, mimicking their habitual Monday-to-Friday sleep. At another, participants had 10 hours in bed – more than every participant habitually slept on weekends.

Compared to six hours of time in bed, sleep extension improved insulin sensitivity by 45%.

Yeah, that’s a lot!

Men will be pleased to learn that blood testosterone levels increased too.

Because participants’ diets were practically the same at each lab visit, this work showed that sleep extension independently improves insulin sensitivity. Nutrition strongly influences insulin sensitivity too, so might sleep extension also alter people’s diets?

Sleep Longer, Eat Better

A study was just published in which adults who habitually slept just five to seven hours a night committed to prolonging their sleep (4). Importantly, there was also a control group of people who did not consciously change their sleep habits. Sleep was then tracked for four weeks, and participants logged their diets using seven-day food diaries.

People in the sleep extension group consumed 10 grams less free sugar each day – about a third of the relevant government’s recommended allowance (*see footnote). Free sugars are added to foods and are practically devoid of beneficial nutrients, so this is surely a favourable outcome.

So, it seems that sleep extension may reduce consumption of foods that can contribute to metabolic problems. If sleep extension influences decision making at the dinner table, might it also alter other aspects of cognition?

Sleep Sharpens the Mind

In a study of the effects of prolonging sleep on cognition, obese adults who habitually slept less than six and a half hours each night aimed to sleep seven and a half hours a night (5). Control participants didn’t change their sleep. A unique aspect of this study was its duration: On average, the sleep extension intervention lasted more than 15 months… so it seems that long-term sleep extension is feasible for many.

During sleep extension, overall cognitive function improved by 7% and attention by 10%. Participants tended to feel less sleepy during the day and also experienced improved memory and executive functioning. (The latter encompasses cognitive skills involved in goal achievement, such as planning, organization, and self-regulation.)

Now, if sleep extension improves brain function, you might expect longer sleep to enhance performance in some sports too, especially team sports necessitating rapid processing of vast amounts of sensory and cognitive information to achieve the desired outcome… like basketball.

Sleep Extension Improves Athletic Performance

In a highly-cited study, the Stanford University men’s basketball team underwent about six weeks of sleep extension after a period of habitual sleep (6). During sleep extension, the men aimed for at least 10 hours of time in bed each night.

While sleeping more, players’ reaction times fell, as did times to complete a multi-directional 282-foot sprint (from 16.2 to 15.5 seconds). Free throw accuracy percentage increased 9%, and three-point field goal percentage rose 9.2%. As if these huge effects were not enough, the players also felt invigorated, less sleepy, and enjoyed greater general wellbeing.

University players have not usually reached their best performances yet, so they probably would have improved somewhat during this time, regardless of sleep extension. Such a rate of improvement is still astonishing, however, and strongly suggests beneficial effects of getting more sleep.

Findings from the above studies indicate many advantageous effects of sleep extension in people who routinely restrict their sleep. Could sleep extension have other applications though?

You bet, and another logical use of sleep extension is as a pre-emptive strategy to offset the unwanted effects of looming sleep loss.

A Way to Counter Harmful Effects of Subsequent Sleep Loss

Let’s say that you know that next week will be so demanding that you’re bound to lose sleep. Might it make sense to “bank” sleep now to buffer the effects of sleep loss?

Banking is an apt analogy here. Imagine that each minute of sleep you get is one dollar, and you’re trying to accumulate a certain amount of wealth in the coming weeks. You know that you won’t be able to save much next week (you lose sleep), so you try to bank more money than usual this week (by extending your sleep).

On to the study (7).

Men and women were randomized into 1) a sleep extension (banking) group that was allowed 10 hours in bed each night, or 2) a group allowed habitual sleep for a week. All participants then had one night in which they were allowed 10 hours in bed before a week of sleep restriction to just three hours each night.

That must have sucked.

After this sleep loss, all participants had five nights of “recovery” sleep in which they had eight hours of time in bed each night (**see footnote).

The participants who banked sleep before sleep loss were more vigilant and were less likely to drift off throughout the sleep loss period. Better still, during recovery sleep, vigilance returned towards pre-sleep loss levels faster in people who banked sleep.

It therefore seems that you might want to bank sleep before your next bout of inevitable sleep loss.

Shortcomings of These Studies

As is perhaps unavoidably true of scientific research, these studies had limitations. Participants were sometimes instructed to not engage in activities like drinking alcohol, which could have influenced results. Some studies didn’t have control groups, so we can’t say that sleep extension caused the improvements seen. This said, studies reporting associations between changes in sleep duration and outcomes strongly suggest causal effects.

An inescapable limitation of these studies relates to participant “blinding”. It is generally preferable to blind participants in experiments, meaning that these people have no idea if they are in the treatment or control group. This is not possible in sleep extension experiments though, so placebo effects are likely (***see footnote).

I’ve previously written about a simple way to improve sleep, but in the next post I’ll give more detailed guidance on how we can all act to benefit from these recent sleep extension studies.

Stay tuned… and sleep tight!

Key Takeaways

Benefits of sleep extension may include:

1. Improved insulin sensitivity.
2. Better dietary choice selection.
3. Enhanced cognitive function.
4. Improved athletic performance, particularly in actions requiring accuracy and speed.
5. Diminished negative consequences of future sleep loss.

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• Many people just don’t record their diets accurately. The researchers therefore did a “sensitivity analysis”, excluding four people who reported unfeasible intakes. After doing so, participants in the sleep extension group now also consumed fewer grams of carbohydrate and fat.
• *Note that eight hours is almost certainly less than participants would have slept after sleep loss and so was probably insufficient for true recovery.
• **“Hawthorne effects” may also be at play in sleep extension experiments (8). Hawthorne effects are changes in participant behaviors that result from being under observation by experimenters.

References

1. Banks S, Dinges DF. Behavioral and physiological consequences of sleep restriction. J Clin Sleep Med. 2007;3(5):519-28.
2. Leproult R, Deliens G, Gilson M, Peigneux P. Beneficial impact of sleep extension on fasting insulin sensitivity in adults with habitual sleep restriction. Sleep. 2015;38(5):707-15.
3. Killick R, Hoyos CM, Melehan KL, Dungan GC, 2nd, Poh J, Liu PY. Metabolic and hormonal effects of ‘catch-up’ sleep in men with chronic, repetitive, lifestyle-driven sleep restriction. Clin Endocrinol (Oxf). 2015;83(4):498-507.
4. Al Khatib HK, Hall WL, Creedon A, Ooi E, Masri T, McGowan L, et al. Sleep extension is a feasible lifestyle intervention in free-living adults who are habitually short sleepers: a potential strategy for decreasing intake of free sugars? A randomized controlled pilot study. Am J Clin Nutr. 2018;107(1):43-53.
5. Lucassen EA, Piaggi P, Dsurney J, de Jonge L, Zhao XC, Mattingly MS, et al. Sleep extension improves neurocognitive functions in chronically sleep-deprived obese individuals. PLoS One. 2014;9(1):e84832.
6. Mah CD, Mah KE, Kezirian EJ, Dement WC. The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep. 2011;34(7):943-50.
7. Rupp TL, Wesensten NJ, Bliese PD, Balkin TJ. Banking sleep: realization of benefits during subsequent sleep restriction and recovery. Sleep. 2009;32(3):311-21.
8. Cizza G, Piaggi P, Rother KI, Csako G, Sleep Extension Study G. Hawthorne effect with transient behavioral and biochemical changes in a randomized controlled sleep extension trial of chronically short-sleeping obese adults: implications for the design and interpretation of clinical studies. PLoS One. 2014;9(8):e104176.