Only 5-6.5 hours of sleep is ideal?

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  • Thread starter SW VandeCarr
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In summary: At the 'group level' figuring out things like amount of sleep needed probably isn't a very feasible investigation. It also depends on what the individual wishes to maximize. For instance, your memory prowess has been consistently linked to a good nights rest. I find for myself that I can function fine on 4-5 hours of sleep, but when I'm trying to learn I need more--Least I want to retain any information. Similarly, I've seen people in very stressful job situations who find a long nights sleep be most comforting--And anything which successfully lowers the cortisol levels ain't a bad thing.
  • #1
SW VandeCarr
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I knew that this amount of sleep (or less) seemed to work for some people. However the general view was that most people needed 7-8 hours of quality sleep for good health. This follow up study in women seems to refute this. The researchers followed over 400 women over 14 years with minimal loss to follow up and discovered the optimal amount of sleep associated with reduced mortality was significantly less (at least for women in southern California).

http://www.eurekalert.org/pub_releases/2010-09/uoc--wsf093010.php

EDIT: It should be understood that this is only one study and for various reasons, should not be considered the last word.
 
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  • #2
That's not the first time I read about research linking amount of sleep with mortality. However, I have never seen statement "all other things being equal" when results are described. This makes me always wonder - what if those sleeping longer are those that don't have to wake up early, because they are already retired, or don't work because of some disabilities?

In other words - what if amount of sleep is just a proxy for something else, something that is more important?
 
  • #3
unless we see the details , its hard to comment on the study

we do not know - what was the cause of mortality in all the cases, it could be anything from car accidents to diseases
 
  • #4
Borek said:
However, I have never seen statement "all other things being equal" when results are described. This makes me always wonder - what if those sleeping longer are those that don't have to wake up early, because they are already retired, or don't work because of some disabilities?

In other words - what if amount of sleep is just a proxy for something else, something that is more important?

Apparently the lead author Kripke has published a lot of studies on sleep. I was looking for this particular paper online but only found the text of the announcement that I linked. I haven't had chance to look at some of the other publications, but this finding was apparently a surprise.

Studies that use large organized observational research project populations, like this study or Framingham, rely on internal controls and use multivariate analysis to control for potential confounding factors. The one you mention is one that probably can be controlled by stratifying on age which is always done in epidemiological studies. Beyond that you would want to control for factors like work status, co-morbidity, etc. Not having seen the paper, I don't know what factors were actually used in adjusting risk ratios other than age.
 
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  • #5
cosmos 2.0 said:
unless we see the details , its hard to comment on the study

we do not know - what was the cause of mortality in all the cases, it could be anything from car accidents to diseases

You're correct. However, to confound an outcome measure, there needs to be an association between the potential confounding factor and both the putative risk or benefit factor and the outcome which could produce the same result . So you would need to show that having an illness or more car crashes is associated with both less sleep and reduced mortality.
 
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  • #6
SW VandeCarr said:
You're correct. However, to confound an outcome measure, there needs to be an association between the potential confounding factor and both the putative risk or benefit factor and the outcome which could produce the same result . So you would need to show that having an illness or more car crashes is associated with both less sleep and reduced mortality.

medical trials require a large sample size to overcome confounding factors.
besides in this study some things are not well understood -since we do not have the details


In real sense -how can a extra hour of sleep have increased risk of mortality i.e. if a person sleeps 7.5 hrs instead of recommended 6.5 hrs

It would seem a extra hour of sleep is always good especially for age group mentioned in the study
 
  • #7
I think "required" amount of sleep is one of those things that will turn out to be far to individualized for following a "general rule"-Much as how "nutritional guidelines" have been adjusted, adjusted again and re-adjusted over the years.

At the 'group level' figuring out things like amount of sleep needed probably isn't a very feasible investigation. It also depends on what the individual wishes to maximize. For instance, your memory prowess has been consistently linked to a good nights rest. I find for myself that I can function fine on 4-5 hours of sleep, but when I'm trying to learn I need more--Least I want to retain any information. Similarly, I've seen people in very stressful job situations who find a long nights sleep be most comforting--And anything which successfully lowers the cortisol levels ain't a bad thing.
 
  • #8
bobze said:
I think "required" amount of sleep is one of those things that will turn out to be far to individualized for following a "general rule"-Much as how "nutritional guidelines" have been adjusted, adjusted again and re-adjusted over the years.

At the 'group level' figuring out things like amount of sleep needed probably isn't a very feasible investigation. It also depends on what the individual wishes to maximize. For instance, your memory prowess has been consistently linked to a good nights rest. I find for myself that I can function fine on 4-5 hours of sleep, but when I'm trying to learn I need more--Least I want to retain any information. Similarly, I've seen people in very stressful job situations who find a long nights sleep be most comforting--And anything which successfully lowers the cortisol levels ain't a bad thing.

I'm not cutting back on my 10 hrs sleep daily just because of this study (slight exaggeration, but I'm not changing my sleeping habits). The issue is if we accept the stated results, how do we explain why women who claimed to sleep fewer hours appear to be living longer? Maybe women who lie about the amount of hours they sleep in the direction of fewer hours just tend to be longer lived. Then you have to explain why women who lie seem to live longer. A sample of over 400 women has a fair amount of statistical power.

In fact, I understand the sleep data were collected in the 1990s and some kind of monitoring device was used to detect sleep patterns. This group has a lot of publications on the internet and have a good reputation as investigators in sleep research. I just want to read the paper when it comes out. So far, I've just seen announcements. I personally don't like these kind of pre-publication announcements. I want to see some details and p values.
 
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  • #9
SW VandeCarr said:
I'm not cutting back on my 10 hrs sleep daily just because of this study (slight exaggeration, but I'm not changing my sleeping habits). The issue is if we accept the stated results, how do we explain why women who claimed to sleep fewer hours appear to be living longer? Maybe women who lie about the amount of hours they sleep in the direction of fewer hours just tend to be longer lived. Then you have to explain why women who lie seem to live longer. A sample of over 400 women has a fair amount of statistical power.

In fact, I understand the sleep data were collected in the 1990s and some kind of monitoring device was used to detect sleep patterns. This group has a lot of publications on the internet and have a good reputation as investigators in sleep research. I just want to read the paper when it comes out. So far, I've just seen announcements. I personally don't like these kind of pre-publication announcements. I want to see some details and p values.
Did they monitor the women during the day for naps?

I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.
 
  • #10
Evo said:
Did they monitor the women during the day for naps?

I don't know. This group is devoted to sleep research so it seems they would have considered naps. However I'm not sure they collected the original data. Again, I'm waiting for the paper.

I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.

Like Bobze says, individual needs vary. Assuming the finding holds up, it may not be a cause-effect relation. I would not recommend anyone change their sleep habits if they feel they are getting the amount of sleep they feel they need. Remember, the quality of sleep is important too. If you feel tired during the day and are able to take a few short naps, they can be very beneficial.
 
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  • #11
i truly believe that sleep time totally depends on the individual. some people can function perfectly at 4 hours of sleep (my sister), yet others such as myself need 8. i cannot function at all when i sleep for only 6 hours. i feel fatigued the whole day and i feel like my eyes are going to pop out. so i really think it depends on the person`s body type and other factors included.
 
  • #12
Borek said:
I have never seen statement "all other things being equal" when results are described.

I take it you don't read econ, then, where "certeris paribus" litters almost every page.
 
  • #14
CRGreathouse said:
I take it you don't read econ, then, where "certeris paribus" litters almost every page.

I meant - I have never seen it when reading about amount of sleep vs mortality.

My own experience with controlling amount of sleep is that's just like trying to squeeze a balloon - when you embrace it and compress, bulges appear in random places. When I sleep short in the night, I am getting sleepy at random hours during a day. Mostly in the nap window around 3-4 p.m., but not only.

Interestingly, I am an owl, and my nap window is about two hours later than Marzena's (she is early bird type).

In case you wonder - no idea how the "nap window" is properly called in English, but it is thing known from the sleep research - there is a time during a day when it is much easier to fall asleep than at other hours, and it happens to be in an early afternoon. (See The Enchanted World of Sleep by Lavie Peretz).
 
  • #15
Maz88 said:
i truly believe that sleep time totally depends on the individual. some people can function perfectly at 4 hours of sleep (my sister), yet others such as myself need 8. i cannot function at all when i sleep for only 6 hours. i feel fatigued the whole day and i feel like my eyes are going to pop out. so i really think it depends on the person`s body type and other factors included.

I agree with you. But the point I'm trying to make is that this study raised a question. They're a reputable group that found an unexpected statistical association. I think this begs for an explanation. IMO here are some possibilities not any particular order:

. The association is indirect (non causal). Some factor or factors are common to women who require less sleep and women who live longer.

. The quality of sleep is more important than duration. Women who sleep less sleep better and this promotes longevity, other things being equal.

. The association is direct (causal). The ideal number of hours of sleep daily is one predictor for longevity and this ideal is less than we thought.

. The association is spurious. Even low p values do not rule out spurious associations.

. The original measurements of hours of sleep under-determined the true amount, possibly because it didn't include naps (courtesy of Evo).
 
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  • #16
Evo said:
Did they monitor the women during the day for naps?

I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.

Evo, honestly speaking, I haven't noticed the inabilities that you mention. Yet, I haven't been following everything you have posted to physicsforums.:smile: (I'm not a troll.lol!) I am concerned about your issues of pain and healing. Perhaps you've discussed this with your physician. I do hope you will feel better soon. :smile:

The American Academy of Sleep Medicine has a section strickly for women. Sleep & Women states the following:

Sleep plays a vital role in promoting a woman’s health and well being. Getting the sleep that you need is likely to enhance your overall quality of life. Yet as a woman you face many potential barriers that can disrupt and disturb your sleep. Overcoming these challenges can help you enjoy the daily benefits of feeling alert and well rested.

Experts suggest that most men and women need about seven to eight hours of sleep each night. Yet there are many differences in how men and women sleep. In general women tend to sleep more than men, going to bed and falling asleep earlier. A woman’s sleep also tends to be lighter and more easily disturbed. Women are more likely to feel unrefreshed even after a full night of sleep.

Women also tend to describe sleep problems using different terms than men. Women may be less likely to say that they feel sleepy during the day. Instead women often describe feeling tired, unrested or fatigued. These expressions reflect feelings of physical or mental exhaustion. Women also may report an overall lack of energy or vitality.

There are many complex factors that may affect how a woman sleeps. Some of these factors change over time. For example, excessive daytime sleepiness is more common when women are in their 20s and 30s. In contrast older women appear to adapt better to periods of sleep loss. This difference has been attributed to the many commitments that compete for a young woman’s time. In particular working moms must balance the demands of their career, family, friends and personal health needs. Yet a recent study provides encouragement for mothers. It showed that having children does not increase a woman’s risk of daytime sleepiness or fatigue.

Common factors that affect a woman’s sleep include:
Life events
Depression
Illness
Bad sleep habits
Medication use
Physical or hormonal changes

Please read on . . .
http://www.sleepeducation.com/Topic.aspx?id=67

Speaking for myself as a woman, I usually sleep straight through the night, unless my cat jumps on the bed and decides to purrrr or snore next to my face in the middle of the night! :smile: A gentle pat to his head seems to shut him up. I normally, during Sunday thu Thursday, go to bed by 10p.m or 11 p.m. and awake by 5:30 a.m. It can vary on Friday and Saturday.

I hope you feel better soon. Take care of yourself.

Best wishes to you,
Mars
 
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  • #17
Here's a synopsis of the full paper. I received the full paper from UCSD as a PDF but I'm sure how to get it posted on PF. I've not been successful before in posting links to PDFs, that I've acquired by email, on PF but I'll give it a try. Maybe someone can help me. The PDF is available online for $31.50 so it may not be in a form that can be posted.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W6N-513F5DM-1&_user=10&_coverDate=09%2F25%2F2010&_rdoc=2&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%236603%239999%23999999999%2399999%23FLA%23display%23Articles%29&_cdi=6603&_sort=d&_docanchor=&view=c&_ct=13&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=32727070e3ae3ad44045c251c9000254&searchtype=a
 
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  • #18
Evo said:
Did they monitor the women during the day for naps?

Now that I have the paper, I can tell you they did. I doubt I'm going to be able to post a link to the full text because Elsevier has proprietary rights. I'll be happy to answer any other questions you or others have. It's a very thorough and apparently methodologically sound study.
 
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  • #19
I did locate from the U.S. National Library of Medicine National Institutes of Health - PubMed the following:

Sleep Med. 2010 Sep 24.
Mortality related to actigraphic long and short sleep.
Kripke DF, Langer RD, Elliott JA, Klauber MR, Rex KM.

Department of Psychiatry, University of California, San Diego, CA, United States.

Abstract:
BACKGROUND: The folk belief that we should sleep 8h seems to be incorrect. Numerous studies have shown that self-reported sleep longer than 7.5h or shorter than 6.5h predicts increased mortality risk. This study examined if prospectively-determined objective sleep duration, as estimated by wrist actigraphy, was associated with mortality risks.

METHODS: From 1995-1999, women averaging 67.6years of age provided one-week actigraphic recordings. Survival could be estimated from follow-up continuing until 2009 for 444 of the women, with an average of 10.5years before censoring. Multivariate age-stratified Cox regression models were controlled for history of hypertension, diabetes, myocardial infarction, cancer, and major depression.

RESULTS: Adjusted survival functions estimated 61% survival (54-69%, 95% C.I.) for those with sleep less than 300min and 78% survival (73-85%, 95% C.I.) for those with actigraphic sleep longer than 390min, as compared with survival of 90% (85-94%, 95% C.I.) for those with sleep of 300-390min. Time-in-bed, sleep efficiency and the timing of melatonin metabolite excretion were also significant mortality risk factors.

CONCLUSION: This study confirms a U-shaped relationship between survival and actigraphically measured sleep durations, with the optimal objective sleep duration being shorter than the self-report optimums. People who sleep five or six hours may be reassured. Further studies are needed to identify any modifiable factors for this mortality and possible approaches to prevention.
http://www.ncbi.nlm.nih.gov/pubmed/20870457

I still like my post#16 on the previous page! Ta ha.
 
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  • #20
The key point here being that there is a difference between self-reported sleep duration and that which is objectively measured. Sleep measured by a wrist actigraph typically less than what is self-reported.

"Time-in-bed, sleep efficiency and the timing of melatonin metabolite excretion were also significant mortality risk factors."
 
  • #21
The National Health Service of England has written in full detail about the article, Mortality related to actigraphic long and short sleep. I will provide a small section of it though I encourage people to read the entire document.

Conclusion
This study’s strengths include the use of an objective measure of sleep, and the long period of follow-up. It supports the findings of other studies with subjective sleep measures, which suggest that very long or very short sleep duration is linked to an increased risk of an earlier death. There are some important points to note:

• The data is for women aged 50-and-over only, and may not apply to men or to younger age groups.

• The actigraph measures movement, so it would not be able to tell the difference between someone lying still while awake and someone lying still while asleep. This may have caused some inaccuracy in the estimation of how long people were asleep, although possibly less than if a subjective measure of sleep was used. The researchers acknowledge that using actigraphs may over-or under-estimate sleep compared to the gold standard way of measuring sleep (called polysomnography).

• The study only measured sleep using the actigraph for one week at the start of the study. Women’s sleep in this period may not have been representative of their sleep patterns over a lifetime.

• It is not possible to say whether duration of sleep is itself affecting the risk of death, or whether another unknown factor is behind both the different sleep patterns and risk of death. Although researchers took into account a number of factors that could affect risk of death, these or other unmeasured factors could still be having an effect.

• Although studies subjectively measuring sleep duration have found a link, a study objectively measuring sleep using the gold standard objective (called polysomnography) did not find a link between short sleep and increased risk of death.

How long we sleep may be affected by many factors, including our internal body clock, our jobs and families, lifestyles, the environment in which we sleep, and stress levels. Although this and other studies have suggested that sleep duration is linked to risk of death, it is not yet possible to say whether you can improve your longevity by simply modifying how long you sleep, without changing any other factors.
http://www.nhs.uk/news/2010/10October/Pages/death-risk-link-to-amount-of-sleep.aspx
 
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  • #22
ViewsofMars said:
The National Health Service of England has written in full detail about the article, Mortality related to actigraphic long and short sleep. I will provide a small section of it though I encourage people to read the entire document.

This is an interesting review that points to the critical metrics and to the question of how to measure sleep in terms of total duration, latency, REM sleep, sleep apnea, etc. One thing that struck me is the reference to a study that employed polysomnography which failed to show a relation between "short sleep" and increased mortality. They don't define "short sleep" nor do they identify the study. However such a finding is not inconsistent with finding that "short sleep",traditionally defined as less than 6.5 hrs, is not only not a risk factor for increased mortality but actually may be beneficial if it's not too short. (Less than 5 hours?)
 
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  • #23
I'm skeptical of the "corellation does not imply causation" type. The "obvious" conclusion is that if those who'd slept longer had curtailed their hours they'd stand a slightly better chance of being alive, but that's not what the study says at all. For all we know, however, those who require fewer hours are simply healthier to begin with - physically, and mentally/emotionally. As a result, they simply required less sleep, and their longevity may have more to do with their overall health and activity levels (exercise) than the length of their sleep.

Anecdotal, but when I'm home, I usually sleep 8-9 hours a night, but when I'm out backpacking, which is significantly more difficult, physically, I typically sleep between 5 and 7 hours a night.

Does this mean that getting less sleep helps me backpack better, or that the exercise of backpacking results in better sleep? Heavens no! It means I need to get a better sleeping pad! Mine's just too old and thin...
 
  • #24
mugaliens said:
I'm skeptical of the "corellation does not imply causation" type. The "obvious" conclusion is that if those who'd slept longer had curtailed their hours they'd stand a slightly better chance of being alive, but that's not what the study says at all. For all we know, however, those who require fewer hours are simply healthier to begin with - physically, and mentally/emotionally. As a result, they simply required less sleep, and their longevity may have more to do with their overall health and activity levels (exercise) than the length of their sleep.

The gist of your observations have already been taken into account in post 15. Do you have anything new to add?
 
  • #25
SW VandeCarr said:
The gist of your observations have already been taken into account in post 15. Do you have anything new to add?

You mean aside from my perspective? Which is, of course, since I hadn't mentioned it before my previously latest post, something new to add. :)

I appreciate your penchant for succinctness, but this is a message forum, not a college text. Repetition is allowed.
 
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1. Is it really enough to only get 5-6.5 hours of sleep?

While the recommended amount of sleep for adults is 7-9 hours, some individuals may function well with less sleep. The ideal amount of sleep varies from person to person and can range from 5-6.5 hours for some individuals.

2. What are the potential consequences of only getting 5-6.5 hours of sleep?

Not getting enough sleep can lead to a variety of negative consequences such as fatigue, difficulty concentrating, irritability, and a weakened immune system. It can also increase the risk of developing chronic health conditions such as obesity, diabetes, and heart disease.

3. Is it possible to train your body to function on less sleep?

While some individuals may be able to function well on less sleep, it is not recommended to try to train your body to require less sleep. Adequate sleep is crucial for overall health and well-being, and attempting to function on less sleep can have negative effects on your physical and mental health in the long run.

4. Can napping make up for not getting enough sleep at night?

Napping can provide a temporary boost in energy and alertness, but it cannot fully make up for not getting enough sleep at night. Additionally, taking long naps during the day can make it harder to fall asleep at night, leading to a cycle of poor sleep habits.

5. How can I determine the ideal amount of sleep for myself?

The best way to determine the ideal amount of sleep for yourself is to pay attention to how you feel after different amounts of sleep. If you consistently feel well-rested and alert after 5-6.5 hours of sleep, then that may be the ideal amount for your body. However, if you frequently feel tired or have difficulty concentrating, you may need to increase the amount of sleep you get each night.

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