Monthly Archives: January 2009

Sleep and the Common Cold

Sleep and the Common Cold

Competency # 7  Sleep

Reference: Archives Internal Medicine Jan 2009 p 62-67

Can you imagine being willing to have your risk for a cold being tested in relationship to how much sleep you get?  That’s what Dr. Cohen and partners were successful in getting  153 healthy men and women to do.  For 14 days they measured exactly how long they slept, and then had the cold virus, rhinovirus, squirted up their noses.  What they found is fascinating.  Turns out that getting less than 7 hours of sleep turns into a 3 times greater risk of getting a cold.  And sleep efficiency below 95% had a 5.5 times increase chance of  getting a cold versus someone who was 98% efficient.

What’s sleep efficiency?  Very simple, it’s the fraction created by dividing the amount of time you estimate you are sleeping divided by the time in bed.  Volunteers were asked each day to report how long it took them to fall asleep, and how often they woke up and had a hard time falling back to sleep.  Those minutes were subtracted from the total.  A running average over all 14 days was added up to get the fractions.

We have known for a while that less sleep results in lower measures of antibody response to both hepatitis A and to influenza vaccination.  We also know that sleep deprivation results in reduced natural killer cell activity and increased levels of inflammatory hormones.  So something magical happens to your immune system while you sleep.  We naturally have about 90 minute cycles of sleep in which we run through different stages of sleep, so 7 hours comes to about 5 cycles.  As we get older, our sleep becomes more fragile and lighter, and our awareness of our bladders becomes more acute.  This study used younger folks (average in the thirties and maximum early 50s) so its implications for folks in their 60s and 70s is uncertain.

This is the first good research to prospectively show the risk.  Apparently sleep efficiency, what percentage of time you stay asleep, is even more important than the total amount.  Time to talk about how to train you to sleep.  That’s next week.

WWW.  What will work for me.  Well, hearing that less than 7 hours is as high a risk for heart disease as high blood pressure, and that I get fatter and more diabetic has me in froth.  So, I’ve made changes.  Seven hours in the sack.  Minimum.  Awake or not.  Interestingly enough, when I know the rule and I look at the clock radio and it’s 430 and I feel wide awake, I tell myself,  “It’s against the rules to get up”.  And sure enough, I’m falling back asleep.  Not getting as much work done.  Oh well… Feels like I’m back in boarding school.

Sleep # 2 Getting Enough Sleep Keeps you From Getting Coronary Artery Calcium

Sleep # 2  Getting Enough Sleep Keeps you From Getting Coronary Artery Calcium

Competency # 7 Sleep

Reference: King JAMA 2008;300(24):2859-2866

Getting a good night’s sleep is critical to keeping you from getting stressed out with your blood sugar.  We learned that last week.  Within just a few days of 5 hours of sleep, you become insulin resistant and start looking like a diabetic.  Bad news.   Now, we have a study telling us all about the arteries in your heart and adequate sleep.  670 patients without known coronary artery disease agreed to participate.  495 finished the study.  It included men and women, Caucasian and African American.  Each one was tested for how much sleep they got by keeping a log (they turned out to be miserable at measuring sleep length accurately) and an “actigraph” which is a little wrist band that measures how often you move.  Turns out that “actigraphy” is a much more accurate measure of actually being asleep and is close to 90% with brain wave measurements of sleep duration.  It’s an easy and accurate measure of how much time you are asleep.  It doesn’t measure if you have sleep apnea or how deeply you are sleeping.   Then, the volunteers measured their sleep and kept a voluntary log of their sleep duration for 6 nights in a row, on two occasions several years apart.

What they found was pretty surprising.  There was a 33% INCREASED  risk of developing calcium in coronary arteries for every hour of sleep below 7 hours.  The mean sleep duration was only 6.1 hours, so everyone in the study was sleep deprived.  That risk reduction is the equivalent of having your blood pressure lowered by 16 mm Hg.  That is unbelievably huge.  The study couldn’t measure sleep apnea, which is known to have a big effect on coronary artery disease.  They looked for it and excluded folks with it, but didn’t test everyone with a sleep study.  That is a weakness of this study.  But they found 4 hours to be higher risk than 5, and 5 was worse than 6, and 6 was worse than 7.  You get the drift?

This is a whole new ball game with sleep.  We need to add sleep deprivation to our list of concerns for heart disease.  If you want a healthy heart, we all need to think of strategies to find the time to give ourselves adequate quality sleep.

WWW: What will work for me?  I’m thinking of strategies to make sure my sleep is better.  I have a bulldog that snores (Bulldogs by definition have ENT issues).  She has been moved to a crate out of the bedroom.  I don’t want my arteries to turn to concrete.   I thought I was being tough working extra hard and bouncing back from a late evening to an early morning job assignment.   Maybe that was true here and there, but as a habit?  I’m aiming for 8 hours in bed, lights out, every night.  How good is your aim?

Getting Enough Sleep Keeps You from being Too Sweet

Getting Enough Sleep Keeps You from being Too Sweet

Competency # 7 Sleep

Reference: Science News 2009 Jan 3;Vol 175 # 1 by Laura Sanders and Nature Genetics 2008 Dec; 41, 77-81 I. Prokopenko et al

Get just 5 hours of sleep for three days in a row (instead of 8) and normal healthy people start to have their blood sugar rise as they become insulin resistant.  We’ve reported on that in the past.  In addition, sleep deprived people start choosing sweet, sugary foods over other foods.   Go back to 8 hours of sleep a night and you are back to normal insulin sensitivity in just a couple of days.  Isn’t that interesting!  You can make yourself diabetic just by missing sleep for a couple of days.  How does that work?

Well, now we know.  It turns out there is a receptor protein on the outside of cells that binds melatonin and sets off sleep-wake changes that occur inside of cells.  Scientists have already shown that depression, obesity and even sudden death all correlate with lack of sleep, so we know that not getting enough sleep is doing something bad to our bodies.  And our bodies are essentially the sum of billions of cells and their individual metabolic needs.  It’s melatonin that’s the key.  Melatonin is the hormone that your internal clock puts out each day through the pineal gland.  It rises at night, helping put you to sleep.  It falls during the day when you are awake and alert.  Your internal clock is pretty accurate, as you well know.  Many of us don’t have to set our alarms because we just wake up within a few minutes of our alarm, shutting it off so that our partner can snooze for a few more minutes.  When it gets dark, melatonin goes up.  You get sleepy.

There is a gene called MTNR1B that codes the melatonin receptor on cells.  When that gene has a single codon change in its DNA with a G instead of a C, a slightly different melatonin receptor protein results.  This changed receptor protein is strongly linked to obesity and a stronger risk for diabetes.  Insulin producing cells in the pancreas also have that melatonin receptor.  If you add melatonin to beta cells that are in a petri dish, those cells make less insulin.  Hence, a lousy receptor and you end up with less feedback to the pancreas causing insulin levels to rise.  Insulin is your storage hormone meant to help you store extra calories.  With higher insulin levels, you put on weight.  Oops.  Get enough sleep and you become more insulin sensitive.

This is the story that’s unfolding.  We are learning our genes.  The human genome project will unpack more and more “gene stories” and soon enough we will be able to read your risk profile for various illnesses by testing your DNA profile.    MTNR1B.  I could have told you that.  When I work nights, I have to have sugar all night long.

WWW: What will work for me.  This study confirms for me the need to be in bed for at least 7 hours.  As I age, my sleep is becoming more fragile.  It’s easier to wake up after just 5 hours.   I’m practicing mental exercises that put my brain back down to rest.  We’ll go over some of those exercises in a week or two.  Sweet, sweet sleep.   Get enough, and you won’t be quite so sweet.