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Issue 13

Table of Contents

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The longitudinal course and impact of non-restorative sleep: A five-year community-based follow-up study

Dr. Cody Misuraca PT, DPT

Key takeaways:
  • Research exists linking sleep quality and quantity to injury and pain, but not all studies show an effect
  • Sleep quality and quantity could be a symptom of psychological state or training stressors, which may have their own impact on injury risk and pain
  • There are several established indicators of poor sleep that we can assess for
  • We can provide recommendations on sleep hygiene but education alone may not be effective in changing sleep quality/quantity
  • Consider referral to a sleep specialist in cases of significant sleep disturbance

 

Everybody knows that sleep is good for us for a variety of reasons, and most people will readily admit that they don’t get as much sleep as they should. If you’re involved in physical rehabilitation you may be familiar with the statistic that sleeping less than 8 hours per night is associated with a 1.7 times greater risk of injury, which comes from a study in adolescent athletes¹.

As with most things in the world of pain and injury, the full story is complex, and the topic of sleep is no exception. To discuss this a bit further, our article this month is a review by Huang & Ihm² looking at literature related to sleep, pain, and injury risk in athletes. The authors of this review start by addressing the question of “how much” sleep is necessary to reduce the risk of injury, and acknowledge that there is no clear consensus on what the exact cutoff is. That said, they cite a handful of studies demonstrating increased injury risk in adults and adolescents who self-report less than 7 hours of sleep per night, as well as a pair of studies demonstrating decreased injury rates in those who self-reported sleeping greater than 8 hours per night.

They also mention one study which found that increased injury rates were observed in endurance athletes who reported suboptimal sleep for about 14 days when compared to those who reported suboptimal sleep for 7 days³. Collectively, these studies suggest that the cutoff for “how much” sleep is optimal hovers somewhere around the 7-8 hour mark, and that suboptimal sleep needs to be maintained for periods of 2 weeks or greater before a deleterious effect occurs.

That said, the authors note that there are four studies in adolescent and adult athletes demonstrating no relationship between sleep and injury risk; these studies¹⁰⁻¹³ were performed in dancers, American and Australian football players, and rugby players, and followed these groups for full competitive seasons using a mix of self-report and wrist actigraphy (activity monitors).

Therefore, the data seems somewhat mixed when it comes to the relationship between sleep and injury, but trends in the direction of an effect existing. It’s important to note that in many of these studies, sleep quantity assessment is based on self-report and so a perceived lack of sleep may be a key variable. This becomes even more interesting to consider when adding to the mix a 2014 study that randomly assigned participants to groups that were told they either experienced sub-optimal sleep or good sleep, regardless of their actual sleep quality⁴.

This study demonstrated decreased performance on cognitive tasks in the group that was told that their sleep quality was sub-optimal, suggesting an expectancy-based effect of perceived sleep quality on performance. Sleep quantity is important, but there is likely some additional complexity past just the number of hours. Huang & Ihm allude to a connection between sleep disturbance and psychological factors such as anxiety and depression, as well as training variables such as acute increases in training volume. It could be that poorer sleep alone is not the sole variable affecting injury risk, and may be a symptom of underlying psychological factors or influxes in training and competitive stressors that have their own unique impact on likelihood of injury.

Huang & Ihm additionally touch on the relationship between sleep quality/quantity and musculoskeletal pain in non-athletic populations. A systematic review of 16 prospective studies with more than 61,000 participants from 10 countries found that suboptimal sleep predicts subsequently reported pain, as opposed to pain preceding poorer sleep⁵. The majority of these studies utilized self-report measures related to quality of sleep, while only 4 of the 16 studies assess self-reported quantity of sleep.

One particular study included in this review assessed baseline sleep quality in more than 2,000 participants and then followed them for 5 years to assess the development of several medical conditions⁶. This study found that participants who reported non-restorative sleep (feeling unrefreshed after waking in the morning) 3 or more times per week were roughly twice as likely to go on to develop chronic pain and arthritis during the follow-up period (odds ratios of 2.06 and 1.88 for chronic pain and arthritis, respectively).

While not all of the studies included in the review by Huang & Ihm demonstrated a consistent relationship between poor sleep and injury, and there may be confounders such as psychological state and training stressors, there appears to be enough data pointing in the direction of a relationship to warrant asking about sleep in our patients and clients. Huang & Ihm cite a consensus statement by the American National Sleep Foundation⁷ that agreed upon the following variables as indicating a poor night’s sleep:

  • Taking more than 1 hour to fall asleep
  • Waking up more than 4 times per night
  • Waking up after ~50 minutes of sleeping
  • Spending less than 64% of time in bed actually sleeping

 

My personal opinion is that when assessing sleep quality in patients and clients, it’s generally best to start with an open ended question such as “how have you been sleeping?” You may obtain most of the information that you’re looking for from this question alone, and you can guide the conversation from there if needed. Asking how many times per night somebody typically wakes up is usually an easy question to answer, but assessing how long it takes to fall asleep or how long they sleep before they wake up comes with the potential problem of encouraging “clock watching,” which could induce additional sleep anxiety.

If somebody already has a pretty good idea of these numbers then it’s useful information to have, but I’m hesitant about asking somebody to formally track this if they aren’t already. Assessing the percentage of time that somebody spends in bed actually sleeping (sleep efficiency) is best measured via a sleep study, so this is not something I’ll typically ask about.

In general, if I have a pretty good idea that somebody is experiencing poor sleep, and they’re open to additional assessment and management, then my next step would be to suggest seeking a sleep medicine consultation. There are recommendations that we can make to help improve sleep. These generally fall under the category of “sleep hygiene,” which includes both the environment and behaviors surrounding sleep. A 2020 review of sleep hygiene and recovery in athletes⁸ makes suggestions that include:

  • Don’t go to bed until tired; get out of bed and do something else if unable to fall asleep
  • Set a static sleep-wake cycle that remains mostly the same every day
  • Establish a set “bedtime routine” such as reading, taking a warm bath, etc
  • Minimize or avoid daytime napping
  • Minimize or avoid non-sleep activities in bed such as TV, phone, and computer use
  • Minimize caffeine after midday and alcohol prior to bed
  • Avoid nicotine products
  • Set up the bedroom to be dark, quiet, and cool rather than warm
  • Shift high intensity exercise to earlier in the day, if possible

 

These changes to sleep behaviors and environment may be helpful for some people, but a systematic review of sleep education programs from 2016⁹ unfortunately demonstrated mixed results for sleep education programs on sleep hygiene knowledge and practice, and ultimately no significant beneficial effect on self-reported sleep quality.

The effectiveness of sleep hygiene education is likely limited in part by effective implementation, so affecting our patients’ and clients’ sleep quality through education alone will likely require additional follow-up and counseling in behavior change strategies. This also highlights the importance of making appropriate referrals to other specialties, such as sleep medicine professionals, for providing high-quality care.

In summary, the relationship between sleep, pain, and injury is complicated, but there does appear to be an impact of both sleep quantity and quality on injury risk and pain. It’s worth asking about sleep with our patients and clients but important to keep in mind that other variables such as psychological state and training stressors could be impacting sleep quality and quantity, and this likely warrants some further assessment.

We can provide recommendations for sleep hygiene but this will likely require follow-up and behavior change strategies to be effective. If a patient or client is having significant difficulty with sleep, and especially if there are psychological factors that could be at play, it’s a good idea to discuss with them seeking consultation with a sleep specialist.

References:

 

Cody Misuraca is a physical therapist and strength coach in Seattle, WA. He works as a sports physical therapist for a community hospital system and also owns Waypoint Strength and Performance LLC, which offers strength coaching services. The views and opinions expressed in this review are those of the writer and do not necessarily reflect the views or positions of any institutions he is associated with.