The Nuance

This Is Why You Sleep So Badly In Summer

The problem isn’t a too-warm or too-bright bedroom.

Every summer, Dr. Michael Grandner sees an influx of patients in his Arizona sleep clinic.

“People start showing up in June saying that, all of a sudden, they just cannot sleep past four or five a.m.,” says Grander, PhD, who is director of the Sleep and Health Research Program at the University of Arizona College of Medicine — Tucson. “They tell me, ‘I have blackout curtains and central air, so light and heat shouldn’t be affecting me. Why am I still waking up so early?’ ”

For years, Grandner didn’t know what to tell them. “To be honest, I was puzzled myself,” he says. “If you’re blocking all those light and heat signals in the bedroom — if your windows are totally blacked out and the temperature is stable — this shouldn’t be happening.”

The phenomenon Grandner noticed in his clinic is well-documented and widespread. Research teams in Japan, Finland, and the United States have observed seasonal fluctuations in total sleep duration, with the shortest sleep times coming in spring and summer (when the days are longest). But none of those research groups figured out exactly why this occurs.

Grandner found an answer of sorts when he spoke with a colleague who is an expert in circadian rhythms. “I told him what I was seeing in my patients, and he said the answer was simple,” Grandner recalls. “He said our bodies are getting signals all day long that entrain our sleep rhythms, and insulating ourselves from light and heat in the early morning isn’t enough to override that.”

If nature wants us to sleep a little less in summer compared to winter, one solution is just to embrace that.

Your body, as you’ve no doubt heard, is equipped with circadian “clocks” that regulate every aspect of your functioning, from the activity of your digestive and immune systems to your sleep-wake schedule. Light exposure is almost certainly the strongest regulator of these clocks; millions of years of evolution have programmed the human body to observe and align itself with the activity of the sun, and the relatively recent arrival of central air and blackout shades isn’t enough to muffle those signals.

While sunlight is the ringleader, many other aspects of your behavior may shift in summertime in ways that reinforce seasonal sleep fluctuations. You’re likely to work out, socialize, drink, and eat later in the day, which may futher adjust your internal clocks in ways that curtail sleep, Grandner says.

What can you do about all this? A better question may be: Why do anything at all?

“If nature wants us to sleep a little less in summer compared to winter, one solution is just to embrace that,” he says. “People want to make the entire universe revolve around their preferences or schedules, but we can’t make the universe conform to our wants.”

Summer only lasts a third of the year. If you’re sleeping six or seven hours during those months, rather than seven or eight, that’s all right. “It’s not a permanent thing,” he says. “You could try going to bed earlier or taking an afternoon nap, but not fighting it is one solution.”

On the other hand, if you feel exhausted during the day — and especially in the morning hours, which is a major indicator of sleep deprivation — it’s worth making sure the conditions in your bedroom are conducive to good slumber. Blackout shades and proper temperature control (A/C, lighter blankets, fans, etc.) can prevent summertime light and heat from messing with your ZZZs. Also — and this is true throughout the year — sticking with a consistent sleep-wake schedule is a key to good, healthy sleep.

But if you’re doing everything right and sleep remains elusive, your best remedy may be to just go with the flow. As the Italian poet Umberto Saba wrote in Insomnia On a Summer Night, “I’ve positioned myself to relax under the stars.”

The price of blissfully long summer days may be a little less shuteye. And that’s okay.