Are you trying everything you can to boost your own or your children’s intellectual abilities, from pills to brain exercises? Then you shouldn’t forget one of the most effective nootropics we know of: sleep. A lack of sleep reduces cognitive performance so much that even exercise and pills combined can’t make up for it.
“Everyone is searching for a magic formula that will improve education across all social classes and ethnic groups—one that will measurably improve test scores, attendance, and the number of students passing their high school graduation exams—without us having to pay for it. Here it is!”
Anthony Portantin, a California senator and sponsor of a bill that prohibits California schools from starting classes too early so that students have time to get a good night’s sleep. If this idea sounds naive or ridiculous to you, know that the law is based on recommendations from medical organizations and was approved in October 2019 to the applause of pediatricians and sleep experts.
Attention naturally underpins all other cognitive functions. It is often an attention disorder that lies behind perceived intellectual shortcomings or difficulties with memory. From a positive perspective, this means that improving attention can boost overall cognitive performance—from academic achievement to work efficiency to slowing cognitive decline in old age. For many people in the fast-paced First World, the most effective way to increase attention is to stop blocking it with sleep deprivation.
Directing attention in the desired direction within the brain begins even before the object of our focus enters our consciousness at all. The brain must “activate” the areas that deal specifically with what it wants to focus on: increasing activity in areas important for studying physics, for example, and conversely, limiting activity in the centers of emotional memories so that the mind isn’t distracted by thoughts of the last date.
Furthermore, the thalamus and other neural structures modulate the weight of various stimuli that compete for our conscious attention. If you’re trying to read, the brain “amplifies” visual sensations while suppressing impulses from the ears or the visceral nerves. Nerve impulses from the visual centers will then be stronger not only metaphorically but also physically. As a result, we are more likely to notice them, and they will also have a more significant impact on the neural pathways as they pass through: we will remember them better.
Attention also affects the individual neurons that process visual stimuli: it increases the sensitivity of the cells that process precisely those stimuli we want to focus on. For example, when reading, our visual cortex becomes more sensitive to shapes resembling letters located in the part of the visual field where the book is situated.
A key role is played by norepinephrine, a hormone released during stress but also an important neurotransmitter—and the center in the brain that produces it: the locus coeruleus (or LC for short). During sleep or rest, the LC neurons remain relatively quiet, whereas under stress they fire at full speed, thereby supporting our alertness—that is, our ability to pay attention to various stimuli from all directions and senses. For peaceful concentration, we need precisely measured and timed firing of LC cells, which “highlight” in the brain precisely those stimuli we want to focus on, while remaining silent in response to others.
It is precisely this delicate mechanism that sleep deprivation can disrupt. Fatigue and drowsiness naturally inhibit the LC. The brain may then respond to insufficient activation by increasing biological stress, which stimulates LC activity. However, stress first stimulates the LC to a nonspecific increase in activity and, second, affects a number of other neural processes, so while it keeps us awake, it makes concentration more difficult.
A number of other, biologically distinct mechanisms that link good concentration to sufficient sleep function in a similar way. In addition to direct links, sleep’s importance for mental performance is also influenced by its effect on emotional and physical difficulties: A reduction in sleep duration by just one hour increases the likelihood of developing depression or anxiety by tens of percent—and also significantly contributes to the risk of obesity, diabetes, and cardiovascular disease.
There is no doubt, however, that we are not getting enough sleep. Both American and Czech teenagers sleep an average of seven and a half hours: 75 minutes less than before World War I and 60 minutes less than the 8.5 to 9.5 hours recommended by experts. This is mainly due to school start times being rigidly set for 8:00 a.m., which forces adolescents to get up at the same early hour every day, while bedtime has been steadily getting later since the Industrial Revolution. And it is precisely the start of the school day that is the focus of current debates—which have resulted, for example, in a California law prohibiting elementary schools from starting before 8:00 a.m. and high schools before 8:30 a.m.
Shifting the school start time from 8:00 a.m. to 9:00 a.m. will translate into better lifelong employment prospects through improved academic performance—from an economic standpoint, this means an extra 500 for each paycheck for students.
The benefits of an extra half-hour of sleep are well illustrated by calculations of the impact of delaying the first bell by one hour, which in practice gives students approximately half an hour more sleep. The conclusion of an American think tank points to an improvement across all subjects of 0.175 standard deviations—a figure that can be thought of as a two-and-a-half-point increase on IQ tests. And such academic improvement also has financial implications: according to the cited model, it results in a 1.4% increase in lifetime earnings.
As a rough guide, we can think of the economic benefit of that extra half-hour of sleep during school years as an extra 500 added to every paycheck we receive over the course of our lives. Simply put, getting enough sleep pays off.
Further reading:
- On sleep and inattention: Arns et al. (2019). Editorial: Time to Wake Up: Appreciating the Role of Sleep in Attention-Deficit/Hyperactivity Disorder.
- On attention focus: Moore: Neural Mechanisms of Selective Visual Attention
- On norepinephrine: Aston-Jones: Brain structures and receptors involved in alertness
- On the decline in sleep duration throughout the twentieth century: Matriccani et al. (2014). In search of lost sleep: Secular trends in the sleep time of school-aged children and adolescents.
