Good sleep is crucial for the brain to restore and regenerate.

(CNN) -- With modern life so packed with activities and stimuli, it's hard to disconnect and fully relax. But that's something our brain needs to repair and restore itself.

The only (almost) safe place our brain can go to relax is sleep. That's why it's essential to get enough sleep.

"What happens in the brain when we sleep, in layman's terms, is essentially that it has the opportunity to not be consciously involved in a change of tasks throughout the day," Victoria Garfield, senior research fellow at the Medical Research Council's Unit for Lifelong Health and Aging and a professor at University College London, told CNN's chief medical correspondent. Dr. Sanjay Gupta.

"As a result, our cognitive function will improve. And you'll feel better the next day because our brain cells had a chance to rest, regenerate and replenish," he said.

Garfield has been studying sleep for a decade. "One of my main interests for the last 10 years has been understanding why we need adequate sleep, why sleep is so important for the brain and body, especially as we age," she said.

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Decades of evidence support the idea that too little or too much sleep is associated with an increased risk of conditions such as diabetes, high blood pressure, heart attack, dementia, being diagnosed with sleep apnea, anxiety and depression, he added.

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Garfield's team recently found that habitual daytime naps are associated with higher total brain volume. The study, published in the journal Sleep Health in June, analyzed data, including MRIs, from more than 35,000 adults in the UK Biobank.

How much bigger? According to Garfield, about 15 cubic centimeters, which his team calculated is equivalent to between 2.5 and 6.5 years of aging. "It's a very important thing in terms of the age of the brain. And we think that's really important because lower total brain volume is linked to certain diseases, earlier mortality and higher levels of stress," he said.

What can you do to make sure your brain is well rested? Garfield has five tips.

Get enough sleep

I apologize to those who think they can get by with 4 or 5 hours of sleep a night, but the truth is that you have to spend much more time face to face with the pillow: ideally 7 to 9 hours per night for adults, depending on age, explains Garfield.

"It's not something people usually think about, and they're pretty surprised when I say, 'Well, but if you don't sleep well, that will bring you all these nasty things,'" he explains.

"There's a lot of emphasis on diet, having a healthy weight, exercising, not having diabetes and all these things," he explains. "People say, 'Oh yeah, but I can sleep 4 hours a night and I'm fine,' and they don't understand that actually the cumulative effects over time are really not good."

Establish a consistent sleep schedule

Go to bed and get up at the same time seven days a week, even if it's hard, Garfield says. This is important because it prepares you to sleep those 7 to 9 hours needed. "A lot of us don't."

Settle in for a short nap

It is no shame to take a nap. "For us, the most obvious thing is to take a nap," Garfield says. "Maybe up to about 30 minutes, because we know that's quite beneficial for the brain. So we literally took a break and tried to fall asleep for a while."

Although his team found a positive effect on the brain associated with short daytime naps, other studies have found that napping is associated with negative outcomes, such as an increased risk of high blood pressure and stroke, and being diagnosed with Alzheimer's.

Get some exercise

Sleeping and napping aren't the only ways to give the brain a break. Moving is also important.

"There's a lot of evidence to suggest that going outside and taking a walk is really beneficial, especially disconnecting from devices and being in touch with nature," says Garfield.

But exercise doesn't have to be a nature walk. The key is to disconnect from work and other activities that demand a lot of attention.

Do something that doesn't make you think

"I think recommending things like meditation and mindfulness is very obvious. But actually, a lot of people find it very difficult, myself included," Garfield says, noting that she can't just switch off her brain.

Garfield recommends other activities that require less brain energy: watching TV (but nothing work-related, Garfield stresses) or even shopping. (Just don't use electronics an hour before going to bed at night.

"It's very important, again, to stress that these things are really individual, and they depend on each person," he said.

CNN Audio's Madeleine Thompson contributed to this report.

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