Feeling Groggy? Here’s How Summer’s Longer Days May Be Affecting Your Sleep—And What To Do About It

Light plays a big role in regulating our circadian rhythm (the 24-hour sleep-wake cycle). The natural rise in your body’s creation of melatonin helps you drift off at night, while a dip in melatonin (and subsequent spike in alertness-promoting cortisol) in the morning is what rouses you awake. On both ends, light influences when and to what degree those hormones are produced—and since there's more light in the summer in general, our sleep can pay the price. “Summer’s longer days can contribute to delayed melatonin production, ultimately leading to sleep issues,” says clinical psychological Michael J. Breus, PhD, chief sleep advisor at Purple.

Recent research backs this assertion: Based on a 2019 study of 1,388 people in Japan ages 15 to 89, all of whom filled out questionnaires about sleep habits once in each season, researchers found an overall tendency to sleep less in summer months compared to winter. That said, the average decrease in sleep duration in the summer was only about 12 minutes, with older participants showing a significantly larger dip and adolescents showing none at all.

"The additional light later into the night in the summer may actually just shift our circadian rhythms back a bit, more than anything." —Sujay Kansagra, MD

Given the shift in our body clocks as we age—naturally shortening the duration of sleep we get overall—it’s possible that the age-related difference in the study is due to young people’s ability to sleep in more readily and make up for later summer bedtimes. “The additional light later into the night in the summer may actually just shift our circadian rhythms back a bit, more than anything,” says sleep specialist Sujay Kansagra, MD, director of Duke University’s Pediatric Neurology Sleep Medicine Program and Mattress Firm's sleep-health expert. “If summer brings a time of increased social activity—say, you’re out and about later, and going to bed later—then I’d encourage you to sleep in a bit if you can, to make up the difference,” he says.

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But since the older you get, the more likely it is that your body clock naturally wakes you up early (even if summer’s extra light keeps you up late), you may, in fact, miss out on sleep in summer months. And with social and work obligations on the table, you might not be able to sleep in and account for the difference, anyway.

With this in mind, it’s important to pay attention to the season’s unique effects on your sleep—particularly an inability to get to bed at your usual time—and work to mitigate any tendency to sleep less in summer, says Dr. Breus. Because at the end of the day (quite literally), clocking the recommended seven to eight hours of night is key to keeping a whole host of body functions in check.

Here are 4 steps you can take to get better quality shut-eye, particularly if you sleep less in summer:

1. Be mindful of your artificial light exposure.

Sure, you can’t control when the sun rises or sets, but you can determine how much artificial light you see, and perhaps more importantly, when that light exposure occurs. “Our brains can’t really distinguish between artificial light and sunlight,” says Dr. Kansagra, “which is why there was a larger difference in our sleep schedules between winter and summer months pre-Industrial Revolution.”

Now that we do have such a high prevalence of artificial light in our lives, though, Dr. Kansagra says it’s worth making a point of reducing your exposure (particularly to blue light from devices close to your face) within 30 to 60 minutes of your bedtime. “The further into the late-night hours that you push that light, the more it suppresses your melatonin production and the bigger effect it has on shifting your natural circadian rhythm back,” he says, adding that this can compound the similar effect of longer summer days.

2. Use the extra daylight hours of summer to be more physically active.

If you’ve ever spent the day swimming or hiking in the heat and slept like a baby the night after, you know the profound effects exercise can have on sleep—namely, that it can help you fall asleep more easily and sleep more soundly. While summer’s extra light can skew your circadian rhythm by keeping you up later, it can also give you more time to get outside and get active, so you sleep more efficiently once you hit the hay. To feel the benefits, Dr. Kansagra suggests doing at least 30 minutes of aerobic exercise per day.

3. Drop the temperature in your bedroom (and your body).

Cooler temperatures promote better sleep. As such, Dr. Breus recommends you set your thermostat to somewhere between 65°F and 70°F. But with summer leading many of us to sleep less as is and delivering hotter weather across the board in the northern hemisphere, it’s all the more essential now to find ways to sleep cooler.

Dr. Breus suggests keeping the shades drawn throughout the day, if you can, to prevent summer’s extra sunlight from steaming up your bedroom (so, you don’t have to crank the AC to compensate later on). And according to Dr. Kansagra, taking a warm shower before you sleep could help, too. Your temperature artificially rises in the shower and then drops afterward, which is an essential part of falling asleep and reaching slow-wave deep sleep, he says. Another way to quicken that temperature-drop process? Sleep fully nude.

4. Take some time OOO.

While both Dr. Breus and Dr. Kansagra suggest sticking to your usual bedtime and wake-up time as much as possible, even as summer showers us with more natural light, you may also find summer provides an opportunity to pay down sleep debt. “That refers to the difference between the amount of sleep you need and the amount of sleep you’re actually getting,” says Dr. Breus, and it can build up over time.

If you’re able to take some time off work in the summer months, prioritize recharging yourself with sleep and resetting your natural circadian rhythm, says Dr. Breus: “This way, when fall rolls around, you’ll actually feel well-rested.”

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