A new study from Baylor University in Waco, Texas found investing in quality sleep now leads to increased cognitive (and overall) health later.

"It's the difference between investing up front rather than trying to compensate later," said Michael K. Scullin, lead study author from the BU Sleep Neuroscience and Cognition Laboratory, in a press release. He added there are substantial changes to sleep quantity and quality as we age. So, to see how these changes impact aspects of our health, like memory consolidation, Scullin and his team reviewed 50 years of existing research.

This body of research included around 200 different studies — some dating back to the late 60s — looking at the link between sleep and brain function in young adults aged 18 to 29, middle-aged adults aged 30 to 60, and the elderly aged 61 and up. Participants were asked how many hours they typically slept, how long it took them to go to sleep, how often they woke in the middle of the night, and how sleepy they felt during the day. These studies also looked at sleep deprivation, naps, and interventions such as sleep medications.

Researchers found that when we’re young, prioritizing adequate deep sleep, “called ‘slow-(brain)-wave-sleep,’ helps memory by taking pieces of a day’s experiences, replaying them and strengthening them for better recollection.” And when we’re in middle-age, naps (so long as a nap isn’t a way to make up for a late night) are an effective way to protect against cognitive decline. In fact, some studies showed sleeping well in middle age predicts better mental function 28 years later.

However, Scullin and his team found as participants grew into old age, they were more likely to wake up throughout the night and get less deep sleep and dream sleep — two components that are necessary for overall brain functioning.

"People sometimes disparage sleep as 'lost time,' but even if the link between sleep and memory lessens with age, sleeping well still is linked to better mental health, improved cardiovascular health, and fewer, less severe disorders and diseases of many kinds."

The bottom line: Investing in a good night’s sleep early on sets us up for improved cognitive and mental functioning later on. When we reach an age in which those cognitive benefits are harder to reap, quality sleep still protects us against disease and poor mental health.

Source: Scullin MK, Bliwise DL. Sleep, cognition, and aging: Integrating a half-century of multidisciplinary research. Perspectives on Psychological Science. 2015.