To the one who has tried the app, the tea, the pill, and the podcast, and is still awake at eleven forty-seven,

There is a particular quality to the sleeplessness of midlife women that most sleep books do not quite capture. The body is tired. The mind is tired. The eyes have been closed for forty minutes and yet nothing has happened. Somewhere between the reading lamp and the last glance at the clock, the machinery of sleep has failed to engage, and the more you notice this, the further away it goes. You are not the first woman to have experienced this. You are one of hundreds of millions in exactly this hour of the night.

There is a very old remedy for this predicament, quietly practiced across India, the Mediterranean, and much of the ancient world, and it involves nothing more than a small dish of warm oil and about ten minutes of your evening. Ms. Whitmore would like to make its acquaintance on your behalf, because the sleep research has, without much fanfare, caught up to it.

The body falls asleep by cooling from the inside out.

The mechanism is quieter than most people realize. Sleep onset is not, chemically speaking, a matter of exhaustion. It is a matter of temperature. Your core body temperature must drop by roughly one degree Fahrenheit before the brain will permit sleep to arrive, and it does this by shunting heat outward toward your hands and feet, where the blood vessels dilate and the warmth radiates gently into the air around you. This is why warm feet are not the opposite of sleepiness. They are, in fact, one of its earliest signals.

The Swiss chronobiologist Kurt Krauchi has spent much of his career mapping this rhythm. His research, published across a series of studies in the late nineteen-nineties and early two thousands, established that adults with sleep-onset insomnia tend to have colder hands and feet than adults who fall asleep easily, and that warming the extremities significantly shortens the time it takes to drift off. The classic Krauchi findings appeared in the journal Nature and remain among the most reliably replicated in sleep science. [source]

This is where the oil enters the story. Warmth applied to the feet accomplishes two things at once. It directly initiates the distal warming that the body uses to release core heat. It also stimulates the dense population of mechanoreceptors on the soles of the feet, which signal the parasympathetic nervous system that the day has ended and the body is safe.

Add the slow, deliberate motion of the hand across the skin, and you have activated a third quiet system: the C-tactile afferents, a set of nerve fibers that respond specifically to gentle, slow touch and that trigger oxytocin release and cortisol reduction. [source]

Add, finally, an oil that carries a familiar scent, and the olfactory system feeds a fourth signal into the same limbic region. A 2013 review by Koulivand and colleagues, published in Evidence-Based Complementary and Alternative Medicine, examined multiple trials of lavender and concluded that its effects on sleep quality and anxiety were modest but consistent across studies. Chamomile has a smaller but similarly favorable literature. [source]

The ceremony asks only for a small dish of warm oil and ten unhurried minutes.

Choose an oil that pleases you. Sesame is the traditional Ayurvedic choice and is slightly warming to the skin. Sweet almond is lighter. Coconut is cooling in the summer months and firm in winter. Any of them will do the work. Warm two or three tablespoons in a small heatproof dish set inside a bowl of hot water, until the oil is comfortably warm to the touch but not hot. A single drop of essential oil, if you would like one, is optional and pleasant. Lavender is the most studied. Roman chamomile is another traditional companion.

Sit at the edge of the bed with a towel beneath your feet. Take a small amount of oil into your palms and rub them together. Then work the oil slowly into one foot for four or five minutes, and then the other, paying attention to the arch, the ball of the foot, and the space between the toes. There is no correct technique. The point is not to perform a treatment. The point is to give the sole of the foot a slow, warm, unhurried attention that it almost never receives.

If you like, warm a small amount of oil between your fingertips and rub gently at the temples in slow circles for a minute or two. The trigeminal nerve, which reads facial warmth as safety, has densely represented receptors here. Ms. Whitmore does not think it is a coincidence that so many old traditions include this closing gesture.

Then put on a pair of clean cotton socks, wipe any excess oil from your hands, and get into bed. The warmth of the feet, protected by the socks, continues to draw heat out of the core body over the next ten to fifteen minutes, and sleep, in most cases, will arrive before you have finished noticing that it is on its way.

The whole ritual takes no more than ten minutes. It costs pennies. It requires no prescription, no app, no ongoing subscription of any kind. And it is one of the few sleep interventions that has been performed by ordinary women, in ordinary households, on every continent, for at least three thousand years.

Ever on the side of small evening ceremonies that ask almost nothing and deliver rather a lot,

Ms. Clara Whitmore