Hari has always had great difficulty sleeping and has generally needed to take the sleep aid melatonin to fall asleep. He also finds it difficult to wake up, and lives on the “permanent cliff-edge of exhaustion” (64). After a few weeks of his digital detox, however, his sleep patterns begin to follow the sun, and he feels more rested and refreshed.

Scientist Charles Czeisler has demonstrated that people who are sleep-deprived suffer from poor concentration: People who had been awake for 19 hours became as “cognitively impaired” as drunken people (66). Czeisler argues that about 40% of Americans and 23% of British people are “chronically sleep-deprived,” which impedes their attention and can cause “attentional blinks” (67)—periods in which people are technically awake, but parts of their brains going to sleep for seconds at a time. This phenomenon devastates their ability to pay attention and process information. Sleep deprivation also affects children, who are more likely to appear hyperactive than drowsy during the day.

Roxanne Prichard, a neuroscientist, argues that humans can safely deprive themselves of sleep temporarily to cope with life events like raising a baby or surviving an emergency. However, using this ability chronically has consequences, including raising one’s blood pressure, causing cravings for sugar and fatty foods, and increasing one’s heart rate.