By Dr. Mercola

Sleep is an integral part of being human, and it’s as essential to life as water, air and food. It’s during sleep that your body recharges, regenerates and heals, that memories are consolidated and emotional events are processed.

Without sleep, your mood, behavior and risk of acute and chronic diseases are rapidly altered. Yet, research shows, too much sleep isn’t good either.

There is, it appears, a ‘Goldilocks zone’ when it comes to sleep – a number that’s neither too much nor too little, but rather is just right, promoting optimal health with virtually no conscious effort on your part.

Too Much Sleep May Be Bad for Your Brain

We hear a lot about lack of sleep in the US, yet there are some Americans who may be sleeping more than they should. In one recent study, researchers revealed that people in their 60s and 70s who sleep nine hours or more each night have a more rapid decline in their cognitive function than those who sleep between six and eight hours.¹

Surprisingly, the so-called long sleepers (nine hours or more) comprised a large portion (40 percent) of the 2,700 study participants. Another 49 percent were considered normal sleepers (six to eight hours) while 11 percent slept just five hours or less.

While scores of cognitive function declined in all three groups over the three-year study, the long sleepers had nearly double the amount of cognitive decline as the normal sleepers. This decline is often seen in mild cognitive impairment, a risk factor for dementia.

Separate research has also shown that sleeping more than nine hours a night may increase your risk of obesity, heart disease, heart attack and stroke.²

Adding Just One Hour of Sleep May Be Highly Beneficial

On the other hand, if you’re not sleeping enough, adding even one hour a night may drastically boost your health. Such was the finding of a yet another study, which set out to determine the health effects of sleeping 6.5 hours versus 7.5 hours a night.

During the study, groups of volunteers slept either 6.5 hours or 7.5 hours a night for one week. They then swapped sleeping durations for another week, yielding quite significant results.

For starters, the mental agility tasks became much more difficult for the participants when they got less sleep. Furthermore, the researchers noted that about 500 genes were impacted.

When the participants cut their sleep from 7.5 to 6.5 hours, there were increases in activity in genes associated with inflammation, immune excitability, diabetes, cancer risk and stress.³

From the results of this study, it appears as though sleeping for an extra hour, if you’re getting less than seven hours of sleep a night, may be a simple way to boost your health.

Taken with the prior study, it also hints that there might be a magic number, or at least a magic zone, of sleep duration that’s generally best. In fact, another new study also revealed that sleeping too much (10 hours or more) or too little (6 hours or less) is linked to increases in chronic diseases, including diabetes, heart disease, obesity and anxiety.⁴

Are Your Kids Misbehaving? Check Their Bedtime

The importance of regular, predictable sleep patterns for children cannot be overstated. Regular bedtimes establish sleep-wake patterns that are crucial for your child’s health, behavior and learning. When this rhythm is interrupted, such as by altering your child’s bedtime each night, they experience the adult equivalent of jet lag on a daily basis.

In one study of more than 10,000 kids (followed when they were 3, 5 and then 7 years old), those with irregular bedtimes had more problems with learning and behavior, including:⁵

• Lower scores on problem-solving tests
• Higher rates of hyperactivity
• More emotional difficulties
• Increased problems dealing with peers

The study’s lead author told Time:⁶

“We know that early child development has profound influences on health and well being across the life course. It follows that disruptions to sleep, especially if they occur at key times in development, could have important lifelong impacts on health.”

The good news is that the effects seem to be reversible, as kids’ behavior scores improved when they adopted regular bedtimes. Of course, it’s not only kids who benefit from a regular bedtime. Adults, too, do best when they go to sleep, and wake up, at the same times each day.

What Is the Goldilocks Zone for Sleep?

Download Interview Transcript

Over the years, I've come to a conclusion that there is no perfect answer to this question because like everything else, the answer depends on a large number of highly individual factors. The general consensus seems to be that most adults need somewhere between six and eight hours of sleep each night, while children need considerably more.

When I interviewed Dr. Rubin Naiman -- a clinical psychologist, author, teacher, and the leader in integrative medicine approaches to sleep and dreams – he agreed; people want a number, but this 'number' must be as individual as the person asking for it.

"I think asking 'how many of hours of sleep should I get?' is like asking, 'Doctor, how many calories should I eat?'" he says. "Of course the answer to that depends on who that person is. It's so individual. It also depends on the quality of those calories. Again, a lot of people are knocking themselves out night after night after night with sleeping pills. They may be getting seven to eight hours, but is it sleep? It looks like sleep. It might feel like sleep, but you know what, it's not really sleep. That's part of the question too—the quality of it."

Dr. Naiman's recommendation is to simply sleep "enough hours so that your energy is sustained through the day without artificial stimulation, with the exception of a daytime nap." I agree with this functional description rather than trying to come up with a specific numeric range. I would add to that guideline, however, the suggestion to watch out for physical or biological symptoms.

For example, when I push myself and don't get high-quality sleep or enough sleep, I'm predisposed to postprandial hypoglycemia. In other words, I am quite sensitive to insulin so when I sleep poorly, it doesn't take much sugar or carbs for it to be easily metabolized and drop my blood sugar—which also makes me really sleepy.

When I get enough sleep, I'm far less susceptible to it.

It’s Restful Sleep You’re After

Rather than getting too caught up in a number, focus on getting restful sleep. You can have the healthiest diet on the planet, doing vegetable juicing and using fermented veggies, be as fit as an Olympic athlete, be emotionally balanced, but if you aren’t sleeping well it is just a matter of time before it will adversely, potentially seriously affect your health.

And we’re not only talking about lack of sleep but also disrupted sleep, such as waking frequently. According to a report by The Sleep Council,⁷ nearly half of those polled responded that stress and worry keep them tossing and turning at night, and nearly 7 million Americans resort to sleeping pills in order to get some rest. While it may be tempting to look for a pill to quickly help you sleep, they will not address any of the underlying causes of insomnia, nor give you truly restful, restorative sleep.

Sure, we all lose sleep here and there, and your body can adjust for temporary shortcomings, but if you develop a chronic pattern of sleeping less than five or six hours a night, then you're increasing your risk of a number of health conditions, including insulin resistance and diabetes, weight gain, heart disease and cancer.

To make your bedroom into a suitable sleep sanctuary, begin by making sure it’s pitch-black, cool, and quiet. Remember, even the tiniest bit of light can disrupt your pineal gland's production of cancer-preventive melatonin and serotonin. For this reason, I highly recommend adding room-darkening blinds or drapes to your bedroom, or if this is not possible, wearing an eye mask to block out any stray light.

The tips discussed so far are among the most important for a restful night's sleep, but they are only the beginning. For more, please read my comprehensive sleep guide: 33 Secrets to a Good Night's Sleep.