Q. Why do I sleep like a log in the winter and have insomnia in the summer?
While there isn’t much research on this particular phenomenon, there is some evidence that seasonal changes can impact sleep patterns, and there are several issues that could cause you to lose sleep in the summer.
Daylight saving time. The most probable culprit is the extra sunlight exposure we tend to get in the evenings during the summer versus the winter — especially for those who live in northern latitudes. This is because light suppresses the body’s production of melatonin, a hormone that plays a role in signaling to the body that it’s time to sleep. So if you’re still soaking up the sun late into the evening — or even under artificial lighting — rather than relaxing in a dimly-lit environment, melatonin won’t be released, and you’ll likely have a harder time falling asleep at your regular bedtime.
Warmer weather. Higher temperatures during the summer can also wreak havoc on sleep. Under ideal conditions, your body temperature starts to fall by a couple of degrees about one to two hours before bedtime in preparation for sleep — and it continues to decline while sleeping, said Leslie Swanson, a clinical psychologist and associate professor of psychiatry in the Sleep and Circadian Research Laboratory at the University of Michigan. This internal cooling effect helps us achieve the deep, restorative stage of sleep known as slow-wave sleep. But “when the ambient temperature is high outside, it prevents our body temperature from falling as quickly to where we want it to be in order to facilitate sleep,” Dr. Swanson said. This not only makes it harder to fall asleep, but it can also cause frequent awakenings during the night.
A more vibrant social life. Beyond light and temperature, it’s also useful to look at your lifestyle during the summer, which may be quite different from your habits throughout the rest of the year. Summer is a time when many of us ease into vacation mode, which can translate into more socializing, drinking and eating late at night. All of these activities too close to bedtime will delay your body’s internal (or circadian) clock and make it harder for you to get the shut-eye you need.
How to sleep more soundly during the summer
The good news is that you are not powerless against the plight of summer insomnia. Here are a few ways to combat this problem.
Stick to a consistent sleep routine. Going to bed and waking up at the same time every day, even on the weekends — no matter how tired you may feel in the morning — will help your circadian clock adjust to your desired bedtime.
Let the sun shine in. During the mornings and throughout the day, open your curtains and go outside as much as possible. Daytime sunlight cues your body that it’s time to be alert and strengthens the circadian clock, which in turn promotes better sleep at night, said Philip Gehrman, a clinical psychologist and associate professor at the Penn Sleep Center at the University of Pennsylvania.
Set the mood. One to two hours before bedtime, make a point to dim the lights, which will trigger your body’s natural production of melatonin. Don’t forget to shut off electronic devices at that time too because they emit blue light, which can be particularly disruptive to sleep. If you need to use a screen at night, Dr. Swanson suggested dimming your device to the lowest possible setting and shifting your screen to “night shift” mode, if it’s available. If you can’t dim the screen or the overhead lights, she also recommended wearing blue light-blocking glasses (often called amber glasses). While there is some debate about their efficacy, there is research suggesting that they can reduce insomnia.
Then, with the lights low, do something quiet and relaxing to transition into sleep mode. “We’re not built to go from 60 miles an hour to zero. We need time to slow down or else it will be hard for us to sleep,” Dr. Swanson said.
That’s why she and other experts said that you should avoid aerobic exercise close to bedtime. They also advised against eating large meals within three hours of sleep (though a small snack before bed is fine). And when it comes to drinking, experts recommended not consuming alcohol in the hours leading up to bedtime because even though it will probably cause you to conk out quickly, it will likely lead to a fitful night of poor quality sleep.
Pay attention to caffeine. “The general rule of thumb is to be cautious of caffeine after lunchtime,” Dr. Gehrman said. “Caffeine can linger in the brain for eight to 10 hours at sufficient enough levels to disrupt sleep.” But he added that the effects of caffeine can vary greatly from person to person.
Cool down your bedroom. When it’s time to sleep, keep your bedroom between 60 and 67 degrees. “We tend to get more deep sleep in a cool bedroom,” Dr. Gehrman said. He even noted that “for some people, once summer hits and they crank up the A/C, they sleep better because they’re keeping their bedroom cooler than they would in spring or fall.” (Wirecutter, a New York Times Company that reviews and recommends products, has tips for keeping a room cool on a budget.)
Avoid distractions. If you can, use room-darkening shades or an eye mask while sleeping. And consider turning on a white noise machine or a fan that hums gently to buffer any distracting environmental sounds.
If you still find yourself tossing and turning in bed, get up and do something calming (like reading a book, meditating or knitting) until you feel sleepy. Only then should you get back into bed. That way you won’t associate your bed with sleeplessness. “We always say that bed should be for two things: sleep and sex,” Dr. Gehrman said.
If some of these things are out of your control, don’t worry. Most people don’t have to follow every one of these suggestions to get a good night’s sleep, Dr. Gehrman added. Still, if none of these strategies help, and your nighttime insomnia starts to interfere with your daytime functioning, seek out a sleep specialist.
Rachel Rabkin Peachman is a journalist specializing in health, science and family.