Only 5-6.5 hours of sleep is ideal?

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?

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.

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.

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.

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.

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.

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.

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