Sleep: A to Zzzzzzzzzz

Take a look at the results from the Heart Scan Blog's most recent reader poll (399 respondents):

How many hours do you sleep per night (on average)?

9 or more hours per night
15 (3.7%)

8-9 hours per night
72 (18%)

7-8 hours per night
152 (38.1%)

6-7 hours per night
111 (27.8%)

5-6 hours per night
38 (9.5%)

Less than 5 hours per night
11 (2.8%)

Like many issues in health, too much or too little of a good thing can present undesirable consequences.

Too much sleep: While psychologists and sleep researchers advise us that at least 9 hours are required to fully eliminate sleep "debt" and achieve optimal vigilance and mental performance, epidemiologic studies have shown increased mortality with this quantity of sleep.

Too little sleep: Getting less than 7 hours habituallly increases blood sugar, appetite, inflammatory measures, and encourages weight gain. Mortality is also increased, just as with sleeping too much. It is also associated with increased likelihood of a positive heart scan score.

7-8 hours per night from a health viewpoint is that Goldlilocks "just right" value: just enough to not erode mental performance substantially, but not so little that inflammatory, insulin-disrupting, and appetite-increasing effects develop.

Of our 399 respondents in the poll, 56.1% (38% + 18%) slept what appears to be an optimal amount for health. While only 3.7% slept too much (9 hours or more), the remaining 40.1% slept too little.

Our informal poll confirms what most of us observe in everyday life: The majority of people shortchange sleep in order to meet the demands of their high-pressure, squeeze-as-much-as-possible-into-every-day lives. But not paying off your sleep "debt" is like not paying the mortgage for a couple of months. You wouldn't expect your friendly neighborhood bank to say, "Oh, you forgot to pay your mortgage? Forget about it. Just pay next month's." Sure, fat chance. But if you don't pay off your sleep "debt," you will pay it back with health.

Comments (5) -

  • Anonymous

    6/23/2009 7:30:43 PM |

    Some thoughts I have about the causality vs. correlation. Those studies that show correlation with increased mortality /disease with sleep times longer than 9 hours per day could suggest that people with deseases sleep longer because of the disease?  Not that longer sleep periods them selfs are the cause of the disease and early death but a sign of troubles in health which need more time for the body to trying to recuperate?

    I personally sleep between  7 - 9 hour per day if I can rest up to my taste, but if I'm stressed I sleep less and if I'm sick I sleep more.

    (Sorry for possible spelling mistakes, I'm not native english speaker.)


  • Dr. William Davis

    6/23/2009 7:40:51 PM |


    Excellent point.

    In fact, I wonder if greater sleep need is, for many, a red flag for hypothyroidism, in addition to other conditions.

  • kris

    6/24/2009 2:04:35 PM |

    Brain study shows differences in night owls, early risers
    Last Updated: Tuesday, June 23, 2009 | 5:36 PM MT  
    CBC News  

    Scientists at the University of Alberta have found there are significant differences in the way our brains function, depending on whether we are early risers or night owls.

    Using magnetic resonance imaging-guided brain stimulation, neuroscientists tested muscle torque and the excitability of pathways through the spinal cord and brain.

    "We found that the brains of morning people are more excitable in the morning and evening people are completely opposite," neurophysiology researcher David Collins said Tuesday.

    "The evening people ... it's almost a perfect storm of excitability in the central nervous system, where the brain is maximal in the evening and the spinal cord is maximal in the evening.... They generate the most force in the evenings," he said.

    David Collins, neurophysiology researcher at the University of Alberta (CBC) "Morning people ... their brains are most excitable in the morning, but their spinal cords are most excitable in the evening," Collins said.  

    The results may suggest that morning people are performing below their maximum possible level at all times of the day because of this, he said.
    Morning person may be steadier

    If you could change morning people into evening people, maybe their performance would be best in the evening, he suggested. This doesn't mean it's necessarily better to be an evening person, he said.

    "A morning person may be a more consistent, steady plodder over the course of the day," Collins said.

    Kaitlin Cleveley, a sports performance researcher at the U of A, likes to begin work around 10 p.m. and go until 3 a.m.

    "Anything that starts in the morning is absolutely brutal for me to try and get up and try and function," she said. This study brings new perspective to training, she said.

    "It's about trying to peak the athlete.... It can help to set up a sleep program, and it can help to reduce jet lag and sort of help you to determine you know 'When should I book the flight?, When should I get there?'" Cleveley said.

    The research has lots of applications, including understanding mental and physical peaks and how people can maximize performance, she said.

    Initially the research was to determine if brain function changes over the day, Collins said.

    The study evolved with some early findings around two subjects in the study. One proved to be an extreme morning person, the other an extreme evening person, he said.

  • Anonymous

    6/27/2009 12:15:28 AM |

    How does napping fit into this?  Does napping count in the "hours per night" or is it separate?  Any statistics on mortality and napping?

    A lot of cultures have an afternoon siesta but Americans tend to frown on napping.

  • Anna

    6/29/2009 6:43:05 PM |

    A close family member just underwent double bypass surgery in the past few weeks (doing well now, though it took a blood transfusion to get over a 2 day slump while in the hospital), after more than a year of symptoms with exertion,  poor stress test results, a lot of career stress recently, etc.  None of us were told though until just before the recent angiogram.   I always viewed this situation as a "when", not an "if", because I had a different view than the AHA's, but it's always "too soon", even if expected.

    The angiogram revealed multiple sites of stenosis in locations not suitable for stents, so double bypass was performed.

    Aside from family history (her father died of CVD at age 50), there were other risk factors, so she faithfully followed most of the AHA guidelines since at least the 80s - regular chol panels (high results), statins, HRT, low fat/high chol, reduced saturated fat, reduced fat dairy, lean meats, lots o' carbs (even lots of whole grains), etc.  

    But obviously, this didn't work (I think it's a recipe for a bypass), because  CVD happened anyway despite all this adherence to  "prevention" (I use that word loosely in this context).  

    Other risk factors include tendency toward "apple" shape, "strong explosive" personality (sort of Type A), and as I suspected, diabetes (though that was concealed from the family until just before the surgery).  On top of that ...(drum roll)...

    and pertinent to this post - 25+ years of working the third shift as a nurse in L & D.  She was *chronically* and noticeably sleep-deficient (very often apparent, even over the phone), not to mention also Vitamin D deficient (her calcium supplement only added a tiny amount).  The coronary calcium scan wasn't done until last year, when there was marked plaque and shortness of breath & fatigue symptoms.  Of course no program such as Track Your Plaque was suggested or undertaken.  It was fate, right? - the family history - nothing could be done to override that, right? Note: if you are reading this with a sarcastic tone, that's about right Wink.

    Talk about an AHA failure to prevent. Everything I've  I shared about about the AHA's misguided approach to prevention, low carb and grain restriction to manage BG and diabetes, and all the other ways to prevent CVD fell on deaf ears.  Still does.  Still keeping my fingers crossed that the bypass arteries don't clog up.