As habits go, cigarette smoking is one of the riskiest. Despite the many reasons people give for smoking—it provides relaxation and stress relief, increased stamina and focus, weight control—the costs are steep. Cancer, emphysema, and heart disease top the list.
Whether smoking also causes insomnia remains to be seen. But research has shown it harms sleep quality. And one reason it’s so hard to quit smoking is the trouble sleeping many smokers experience during nicotine withdrawal: thirty-nine percent of smokers report having insomnia when they try to quit smoking. Using polysomnography, two teams of scientists—one at Johns Hopkins University in Baltimore and the other based in Freiburg, Germany—set out to measure smoking’s impact on sleep, and here is what they found.*
Smoking Delays Sleep Onset
Smokers in both studies took longer to fall asleep than nonsmokers. The Baltimore study included 6,400 participants enrolled in the Sleep Heart Health Study. On average, the smokers took over 5 minutes longer than the nonsmokers to fall asleep. In the Freiburg study, comprising 88 participants, the smokers took about 25 minutes to fall asleep while the nonsmokers fell asleep in 16 minutes.
Smoking Shortens Sleep Time
Smokers in both studies had shorter nights. Smokers in the Baltimore study slept 14 minutes less than nonsmokers, on average. Smokers in the Freiburg study slept about 11 minutes less than nonsmoking controls.
Smoking Is Associated with Less Deep Sleep
Smokers in the Baltimore study did not sleep as deeply as nonsmokers. Smokers got about 14 percent less deep sleep, and had 24 percent more stage 1 sleep (the lightest sleep stage), than nonsmokers. This shift toward lighter sleep is consistent with data from previous studies, showing that compared with people who have never smoked, smokers tend to (1) report their sleep is less restorative, (2) have more trouble waking up in the morning, and (3) feel sleepier in the daytime.
Smoking Is Linked to Abnormal Breathing & Leg Movement
People diagnosed with sleep apnea or restless legs syndrome were excluded from the Freiburg study. Even so, compared with nonsmokers, smokers in the study had more abnormal breathing as they slept. They also experienced more leg movements. Their sleep was more fragmented due to wake-ups caused by the leg movements. And they reported feeling less refreshed in the morning.
Here’s the Bottom Line
Most of these changes have also been noted in people wearing nicotine patches, so nicotine is likely responsible for at least some aspects of the compromised sleep that smokers have. And nicotine is clearly the prime suspect here: in the brain, it affects production of many of the same neurotransmitters that play a key role in sleep–wake regulation. E-cigarettes contain nicotine as well.
The long-term consequences of smoking are serious, and if the prospect of cancer, emphysema, and heart disease isn’t real enough to make you think twice about continuing, then the harm that smoking causes to your sleep may not be, either. But if you smoke and wonder why you’ve got insomnia, the nicotine might be to blame.
*All findings reported in this blog post were significant.