Another "Eight" Myth

As you may know by now, eight 8 ounce glasses of water a day is more an old adage than medical advice. This is largely due to the fact that we do not all weigh the same, and thus don't all need 64 ounces of fluid. Also we don't all do the same things with our bodies, so some need more and some need less.
Today I am writing about a research study on the sleep needs of person's over age 65.
The study was mentioned and explained in a USA Today article by Kim Painter. Her article was good, but it did not explain one issue that I thought was relevant. Being the curious girl I am, I contacted the lead author, Derk-Jan Dijk-Professor of Sleep and Physiology -Director, Surrey Sleep Research Centre in the UK. He forwarded the actual research article to me.
My post today comes from Ms. Painter's article, Dr. Dijk's study and the experts interviewed by Ms. Painter. Of note, no group in the study is getting eight hours of sleep and according to a side bar in the article, the most sleep - in the 20-30 year olds, was just over seven hours and the other two groups, 40-55 and 66 and above were getting six plus hours.
The study explored whether or not the less hours of sleep in the older group was truly a deficit that led to functioning problems during the day or over time. The research indicates that it does not. However, it was a small study and is not conclusive.
The scientists did require that the volunteers be healthy. That was my issue - what defines healthy? Dr. Dijk sent me the article so that I could look at the criteria and he said that I could email him again if I needed more information, but I felt that he had already been generous.
The volunteers did under go a medical and psychological screen at the first visit. They were not to have any sleep disorders and they could not be on any mood or conscious altering drugs (think of any meds for mental illness, many pain meds, and meds for insomnia). The paper did not indicate if weight or chronic disease was a factor. Thus, I am making an educated assumption that the people in the study could have a chronic illness (how many over age 60 do not have one ?) but that the illness had to be controlled.
So the study was cool. The older persons did take longer to fall asleep and historically, older persons do also have sleep disturbance. In the experiment, they did interrupt the sleep of the younger and older subjects, so that everyone had less SWS (slow wave sleep) time. The researchers tested for day time sleep and also for functioning, alertness, energy and relaxation. Most persons who had their sleep disrupted would fall asleep during a designated nap period the next day. What the researchers found was that the older persons did not have that daytime sleep propensity when their sleep was disrupted or shallow - on its own, or when they slept on average, 40+ minutes less than younger persons.
All this meaning, it could just be possible that our sleep needs DO change over time and that we can function well with less sleep. This is far from an agreed upon theory however. Sleep is restorative and effects many different levels of our functioning, from our immune system to our memories. If one lacks hours of sleep or has restive sleep, the replenishment may not occur.
Of note, under normal conditions, it does not appear that six to seven hours of sleep lead to daytime drowsiness, thus - it is NOT normal and should be reported to a physician.
Another thing I liked in Ms. Painters article was a statement by the director of sleep research at the National Institutes of Aging. He introduced the idea of sleep ability vs sleep need. That is interesting. If one's need is greater than one's ability than certainly a sleep disorder may be at hand. However, if need and ability are equal, even at six hours, than one does not need to "fret" over not getting that 8 hours. Certainly, that would be counterproductive and interrupt the sleep more.

I still wonder about the differences that might occur if we compared older persons that are fit and active vs those who are sedentary, overweight and who have diabetes, HTN, or other cardiovascular problems.