Human Limits

The usual article on sleep and health focuses on how we are all sleep deprived and the bad things this does to us.  The story is pretty simple: chronic low grade sleep deprivation leads to systemic inflammation, weight gain, excessive eating, and hormonal changes that are associated with all sorts of long term health issues.  The drowsiness also leads to poor judgment, more accidents, more eating and other shorter term issues.   This is all being made worse as technology ranging from artificial lighting to smartphones that make our days longer and longer.  Many of us then get up earlier and jump start the day with a mega dose of caffeine.

 

The epidemiologists tell us that 7-8 hours per day of sleep is the optimal health sweet spot for most of us.  People who routinely get by on 5-6 hours of sleep have about 1.5 times the relative risk of death from coronary heart disease.  Interestingly, the risk is about 1.4 times for those who sleep a lot:

 

“Too little or too much sleep are associated with adverse health outcomes, including total mortality, type 2 diabetes, hypertension, respiratory disorders, obesity in both children and adults, and poor self-rated health. The relationship between duration of sleep and vascular events is U-shaped, suggesting that different mechanisms may operate at either end of the distribution of sleep duration.”

 

If you are worried that you are getting either too little or too much sleep there are some simple steps you can take that work for most people to promote better quality sleep.  Highlights include:

• Avoid napping
• Limit the use of (caffeine) to earlier in the day
• Morning exercise
• Avoid large meals before bedtime
• Get adequate exposure to natural light
• Establish a bedtime routine
• Use your bed for sleeping as opposed to reading and watching TV
• Make where you sleep a comfortable place

As a result primarily of the obesity epidemic there is also an epidemic of sleep disturbed breathing.  There is a simple questionnaire that can help determine if you have the problem and need medical follow-up.

 

Sleep & Exercise Performance

What about short term sleep deprivation and exercise performance?   What happens when you have a competition and only get four hours of sleep the night before?  What if you are in a multi-day event with little time for sleep?  Many of the studies on this topic are from the 1980s and 90s and they tend to show that even 30 hours of total sleep deprivation does not do much to VO₂max.  Studies on longer term submaximal exercise are limited but they tend to show exercise time to exhaustion is reduced but with some subjects effected far more than others.   One general finding appears to be that people rate whatever they are doing as harder to do when sleep deprived.

 

Countermeasures

An interesting source of data on exercise performance and sleep deprivation comes for the literature on physical conditioning and military Special Forces.   These individuals frequently do very demanding night operations for several nights in a row with limited opportunities for daytime sleep.   In a series of Canadian studies that simulated several days of night operations, caffeine (1-200 mg) improved run time, cognitive performance, and marksmanship.

Another interesting idea is that recovery from days in a row of vigorous activity with short sleep can be enhanced by protein supplementation.  There is a lot of discussion in military nutrition circles about 20-25 gms of protein before sleep during periods of high stress physical activity.  The idea is that muscle mass will be better preserved during periods of physical stress, sleep deprivation, and limited calorie intake. It would be interesting to know if professional cyclists are adopting similar strategies during the big stage races.

 

Closing Thought

As part of my medical training I have probably spent more time than most people both working and working out while sleep deprived.  There are short term strategies to deal with it, but sleep deprivation is no fun and my goal in middle age is to avoid it as much as possible.  Advice that is easier to give but harder to act on in our high strung world.

 

This entry was posted on Wednesday, December 11th, 2013 at 12:43 pm and is filed under Research and Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.