Analysis: People with a poor sleep profile had brains that appeared nearly one year older than expected based on their age By Abigail Dove, Karolinska Institutet We spend nearly a third of our lives asleep, yet sleep is anything but wasted time. Far from being passive downtime, it is an active and essential process that helps restore the body and protect the brain. When sleep is disrupted, the brain feels the consequences – sometimes in subtle ways that accumulate over years.