It may one day be possible to reap some of the benefits of sleep without ever closing our eyes. Stimulating specific brain activity in awake mice led to some of the same effects as deep sleep, including a boost in memory.

“It should be possible, at least in theory and to some extent, to replicate these results in our species,” says at the University of Oxford, who wasn’t involved in the research. “It would be fascinating to explore whether artificially inducing [this activity] during waking [hours] in humans can result in a subjective feeling of being more refreshed and rested afterwards.”

Sleep is thought to be an essential way for the brain to carry out most of its maintenance work. This includes synaptic homeostasis, the process whereby the brain declutters the thousands of new neural connections made during the day – storing important ones and weakening or cutting away ones that aren’t as necessary.

During non-rapid eye movement (NREM) sleep – the deep sleep state that makes up around 80 per cent of sleep in adults – the brain’s cortex repeatedly fires signals at the exact same time and then shuts those neurons off, in a pattern called slow-wave sleep activity. “This has been linked to synaptic homeostasis, and may be a key mechanism underlying sleep’s restorative functions,” says at the University of Wisconsin-Madison.

Cirelli and her colleagues wondered if a small part of the cortex could be nudged into entering this deep sleep state while an individual is still awake. Some animals do this naturally, such as dolphins, ducks and fur seals, in which one half of the brain enters NREM sleep while the other remains alert and vigilant for predators.

To see if a similar state could be induced, the researchers genetically engineered mice so their neuronal activity could be switched off using light. They implanted a probe into one half of their brain and kept the mice awake for five hours by giving them new things to explore. Near the end of this time period, the light probe was repeatedly turned on and off for 30 minutes, mimicking NREM sleep.

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Afterwards, when the mice were allowed to sleep, brain recordings showed that the stimulated side of the brain didn’t show the usual signs of exhaustion caused by sleep deprivation. “Because that small part of the brain did its decluttering while awake, it no longer needed extra deep sleep afterwards,” says Cirelli.

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Next, the researchers wondered whether forcing sleep during wakefulness boosts memory. So they placed the genetically modified mice in a square box with carpet that had the same texture on both sides of the container. After 15 minutes of exploring the space, the mice were assigned to either a sleep group, a group that was sleep-deprived for 1 hour, or a group that was sleep-deprived for 1 hour but received the artificial deep-sleep stimulation.

The next day, the mice went back into the box, but one side of the container had a new texture. Mice are naturally drawn to novelty, so the researchers measured how much they remembered the old environment by the amount of time they spent on the new side. They found that the sleep-deprived mice that received no stimulation seemed to struggle to tell the new and old side apart, while both the sleep group and the sleep-deprived mice that received the stimulation spent more time on the new side.

The team plans to study whether similar effects could come about in people if this brain activity were induced non-invasively via transcranial electrical stimulation. However, Vyazovskiy stresses that sleep can probably never be replaced. “Sleep is of two kinds – NREM and REM [rapid eye movement] – and we still do not know what it is about the alternation of these two states that makes sleep complete,” he says.

If you are hoping to boost your health this year, there is some good news: making even small tweaks to your sleep, diet and exercise habits could have a big impact on longevity.

“Just around 5 extra minutes of sleep per day, about 2 minutes more of moderate-to-vigorous physical activity – like a brisk walk or taking a flight of stairs – combined with just an extra half-serving of vegetables per day is linked to an additional 1 year longer lifespan,” says at the University of Sydney, Australia.

It is no surprise that getting enough sleep, exercising and eating well are crucial to a long life. Countless studies have shown this by, for instance, comparing the lifespan of people who eat a healthy diet to that of people with an unhealthy one, or by of at least 150 minutes of moderate-intensity physical activity per week.

But it was unknown how very small lifestyle changes affect our lifespan and healthspan, which is the number of years spent in good health.

To fill this gap in our knowledge, Koemel and his colleagues analysed sleep, dietary and physical activity data from nearly 60,000 adults, aged between 40 and 69, from the UK Biobank project. The participants completed surveys that asked them to recall how often they ate various types of food, such as fresh fruit or processed meat, over the past year – with their diets being ranked from poor to healthy on a scale of 0 to 100. A few years later, they wore movement trackers on their wrist for a week to measure their exercise and sleeping habits, and their mortality and health records were tracked over a subsequent follow-up period of eight years.

Using these measurements, the researchers pinpointed the bottom 5 per cent of participants with the least healthy lifestyles: they slept for around 5 hours each day, engaged in about 5 minutes of moderate-to-vigorous physical activity daily and scored about 35 on the dietary scale, on average.

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The researchers then used a statistical model to estimate that, compared with these least-healthy participants, those who slept for about 5 minutes more each day, engaged in moderate-to-vigorous exercise for about 2 minutes longer and ate the equivalent of an extra half-portion of vegetables daily lived for a year longer, on average.

This combination of small lifestyle changes had the same effect as making larger shifts in only one aspect of lifestyle – for instance, sleeping for an extra 25 minutes without altering exercise or diet, says Koemel. “When we package lifestyle changes together, we get more bang for our buck and we reduce the overall requirement from any one behaviour.”

Compared with the least healthy group, those who got an additional 24 minutes of sleep, spent an extra 4 minutes doing moderate-to-vigorous physical activity and ate the equivalent of an additional portion of vegetables were estimated to spend an additional four years free of major chronic conditions, namely dementia, cardiovascular disease, chronic obstructive pulmonary disorder and type 2 diabetes. “Individuals might not just be gaining an additional lifespan, but actually extending their quality years as well – that’s quite a terrific find,” says Koemel.

Making small lifestyle tweaks was estimated to bring similar benefits even for the average participant, who slept for about 7.6 hours each day, got around 31 minutes of moderate-to-vigorous exercise daily and scored roughly 54 on the dietary scale, says Koemel. The analysis suggested that the optimal lifestyle to achieve the biggest benefits included 7.2 to 8 hours of sleep a day, with 42 minutes of moderate-to-vigorous exercise and a score of 58-73 on the dietary scale.

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The findings support a second study published this week, which analysed mortality and exercise data – measured via movement trackers – from more than 40,000 people, aged 64, on average, across Norway, Sweden and the US. at the Norwegian School of Sport Sciences in Oslo and his colleagues fed this data into a statistical model and predicted that, if the vast majority of the population in those countries – except for the most active 20 per cent of people – engaged in an extra 5 minutes of moderate-to-vigorous exercise per day, about 10 per cent of deaths could be prevented in the following eight years, on average.

But both studies have some limitations. For instance, dietary recall surveys are prone to error because people forget what they have eaten, and it is impossible to know whether a week of physical activity or sleep data is really representative of someone’s general habits over longer periods, says at Columbia University in New York.

Further research is needed to establish how long lifestyle tweaks need to be made for before they bring benefits, says Koemel. It is also important to explore how the findings vary between age groups and whether they apply in non-Western, low- and middle-income countries where physical activity levels, diets and the rates of chronic conditions vary, he says.