Sleepyhead by Henry Nicholls

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Americans, presumably the lion’s share of the audience for Sleepyhead: The Neuroscience of a Good Night’s Sleep (new from Basic Books), are currently sleep-deprived to historic extents. That elusive creature, the average American, sleeps less often and less effectively than ever, pressured by work and school and entertainment and the relentless clamor of the social media platforms to which they are gravely addicted. This is very nearly equally true for the rest of the world, where the sale of over-the-counter sleep “medications” is a multi-million dollar industry precisely because people everywhere in all walks of life are fighting against the biological necessity of sleep with manic perseverance. In addition to the stress of work and money, we also carry with us at all times bright interactive devices we have configured to keep us constantly engaged with the outside world. For most people, their cellphone is the last thing they check before snatching what little sleep they’ll eventually get and the first thing they check when that sleep raggedly ends.

In Sleepyhead, veteran science journalist Henry Nicholls joins the ranks of experts to stress that such sleep, bracketed by the stimulation of backlit screens and often periodically interrupted by that stimulation at different points during the night, is almost worthless. Humans bombarding themselves with colorful, engaging stimuli right up until the moment they shut their eyes are placing impossible demands on biological systems that evolved hundreds of thousands of years before iPhones and Netflix. Humans are among the comparatively few species on Earth who required monophasic sleep, in which there’s a clear dividing-line between sleep-time and awake-time. The hours of unconsciousness alone are only part of the equation; equally important is how you get to those hours, and how you leave them.

There’s no ironclad norm, as Nicholls points out:

Humans have evolved to sleep more than a giraffe and less than an opossum. We like to sleep during the hours of darkness. We are a species that seems to need somewhere between six and eight hours of sleep in a 24-hour period. But even within a single species there is tremendous variation and sleep can vary considerably from one person to the next. Our genetics, gender, age, the seasons and our cultural traditions, not to mention the whims of everyday life, all have an effect on how we sleep.

Some people can barely function with less than ten hours of sleep out of every 24; others can scrape by on 6 (usually running the whole time a “sleep deficit” that slows their reflexes, heightens their mood-swings, shreds their coronary system, and makes them prone to abominations like napping in public); there are a few documented cases of freaks who survive happily on less than four hours out of every 24. But in all cases, the duration is less important than the depth: the enormous complexity and wattage of the human brain requires deep sleep, a period of immobile catatonia that’s crucial but still only partially understood. Nicholls returns again and again to the importance of deep sleep, although also pointing out that all the stages of sleep are important, a whole-brain bath of calm and restoration:

There is evidence too that non-REM sleep may be a time for the brain cells to carry out important housekeeping duties, replenishing stores of neurotransmitters and calcium, for instance. Brain cells also appear to shrink somewhat during non-REM sleep, allowing more room for cerebrospinal fluid to percolate and wash away toxic metabolic waste.

Sleepyhead takes readers through the whole world of sleep: sleep patterns, sleep biology, sleep disorders, sleep diseases, and, doggedly if fruitlessly, sleep remedies. Most of these remedies have become familiar from books and online forums in recent years, as growing numbers of people realize that they’ve allowed sleep to be crowded into a small and fractured corner of their lives. The basics are always the same: turn off your electronics well before you go to bed, keep your sleeping-place dark and cool, give yourself the number of hours you need, and be generous in estimating those hours. In short: treat your sleep with the respect it deserves, regardless of how enticing some Twitter stranger’s latest multi-part rant might seem. All the most conscientious books in the world won’t matter if over-stimulated readers don’t recognize that the over-stimulation itself is the problem, but Sleepyhead does everything it can.

Steve Donoghue was a founding editor of Open Letters Monthly. His book criticism has appeared in the Boston Globe, the Wall Street Journal, The Spectator, and the American Conservative. He writes regularly for theNational, the Washington Post, the Vineyard Gazette, and the Christian Science Monitor. His website is http://www.stevedonoghue.com.