Caught in the Diurnal Course

 

"The Inner Clock

By Lynne Peeples

Riverhead, 368 pages, $30

One summer evening in 1986, 33-year-old Derek Naysmith was setting up a fireworks display. In a split second, everything went wrong: A firework exploded in his face. He was rushed to the hospital, but there was nothing the doctors could do to save his eyes. Damaged beyond hope of repair, they had to be removed.

Such a horrific accident was sure to have consequences. There would be reconstructive surgery, followed by the adaptations required for sightless living. But for Mr. Naysmith, something else went awry: He couldn't sleep at night. A month after the accident, Mr. Naysmith's sleeping schedule was at odds with those of his wife, children and much of the diurnal (that is, night-sleeping) world. Yet he wasn't thriving as a nocturnal person, either. "With the loss of his eyes," writes Lynne Peeples in "The Inner Clock: Living in Sync With Our Circadian Rhythms," Mr. Naysmith had become "time blind." He had lost the ability to "reset his inner clocks" to the sun.

When Earth was first formed out of cataclysmic dust, heat and gasses about 4 1/2 billion years ago, the daily rotation of the planet took six hours. By the time the earliest microbial forms of life emerged at least three billion years ago, things finally settled into a 24-hour day -- and we've been here ever since. We scarcely give a thought to these astronomical features, but our planet's orbit, the moon's gravitational pull, the tilt of our axis and those precious 24-hour cycles are intimately bound up with all existence -- including our own. Ms. Peeples, a science journalist, explains that early organisms had to "anticipate the sun's position" and "optimize their journeys to appropriately avoid or reap its rays." To do that, they developed a means of sensing wavelengths of light -- especially blue, which penetrates deepest into the ocean. And so the earliest organisms learned to calculate time by photons. In other words, life could track both time and color before the development of eyes. Daylight and Earth's 24-hour clock are at the very heart of evolution.

"The Inner Clock" offers a rich history of what makes us tick, so to speak, paired with fascinating modern discoveries about how circadian rhythms influence our daily lives. We now understand that sleepless nights erode our health, leading to an increased risk of diabetes, obesity, heart disease, depression and more. We've also learned how to optimize our biological clocks: There are "right" times of day to take medicine, pass tests, exercise and eat. Our ancestors were not meant to be up and working after dark, and so we have digestive systems designed for lengthy downtime; even our gut flora rhythmically fluctuate during the day. Time-restricted eating has been called a life-giver, a means of enhancing longevity. Which is why a pizza at midnight is never a good idea.

Ms. Peeples reminds us of the popular adage "eat like a king in the morning, a prince at noon, and a peasant at dinner." (It's often paired, usually by well-meaning parents and grandparents, with other pearls, like "early to bed and early to rise. . . .") Some of this received wisdom appears to be correct after all. The author cites studies demonstrating that those who eat large meals early in the day have lower blood-sugar levels than those who eat lightly until dinner. Meanwhile, insulin sensitivity is 54% higher at midday than at midnight. That doesn't mean we should gorge in the morning; the melatonin that our bodies release to help us sleep needs time to metabolize and clear our system; otherwise, we risk confusing our inner clock and throwing off our circadian rhythms.

It's not just about being tired. Disruptions to our sleep and wake cycles can lead to inflammation, making us prone to a host of autoimmune conditions. (The World Health Organization has even declared night-shift work "probably carcinogenic," or potentially causing cancer.) The reason is less about sleep and more about misaligned clocks. Ms. Peeples explains that our circadian rhythms are so timed with the Earth's cycle that even in studies conducted in complete darkness, most people still operate on a 24-hour (or nearly 24-hour) cycle. Our primary or core clock seems to be located inside our brains and generally set by our eyes as they register wavelengths of light. But we do have other clocks, including ones in our liver and our digestive system. Some of the worst effects of disrupted circadian rhythms -- something Ms. Peeples calls "social jet lag" -- have to do with the clocks falling out of sync. One theory suggests that hangovers may be a timing problem, as a sleep-deprived brain and an overworked liver struggle to reconnect.

Ms. Peeples's conversational, often humorous style is a delight, and she frequently offers herself as a test subject by climbing into lightless bunkers or forgoing her morning cup of coffee. "The Inner Clock" provides advice on how to reset and restore our internal rhythms; it also sounds a timely warning. Most of us live, work and play under artificial light. From the blue-tinged screens that we stare at well into the night to the light-emitting diodes (LEDs) that can mimic daylight, all this false daylight hijacks our circadian rhythm, scrambling our production of melatonin and leaving us in a state of protracted jet lag. As we have lost the division between night and day, no wonder many of us struggle to establish a sense of internal time. As we approach yet another seasonal "time change," we are well overdue to resynchronize. "The Inner Clock" attempts to show us how.

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Ms. Schillace, the editor in chief of the journal Medical Humanities, is the host of the "Peculiar Book Club" podcast and the author of "Mr. Humble and Dr. Butcher."" [1]

1. Caught in the Diurnal Course. Schillace, Brandy.  Wall Street Journal, Eastern edition; New York, N.Y.. 01 Nov 2024: A.13.