Health: Sleep, Snoring and the Blues

I started snoring in the middle of the night last week. The next morning, my wife was as nice as could be about it, but I could tell it bothered her. She hadn't been able to wake me or push me onto my side to get me to stop, and she ended up spending much of the night with her pillow on her head, trying to block out the noise.

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I know that everybody snores from time to time—even my 90-lb. dog and my 15-month-old baby—but I was still embarrassed. I suspected my snoring had something to do with the onset of the fall allergy season—a theory supported by a study of French allergy sufferers published in the Archives of Internal Medicine last week that found that most of them were troubled by some kind of sleeping problem and that 35% had full-blown insomnia. (See the top 10 medical breakthroughs of 2008.)

People joke a lot about snoring and insomnia, but they're no laughing matter. In fact, they are just the opposite, according to a new study exploring the relationship between sleep-related breathing disorders and clinical depression.

The research, which was also published in last week's Archives of Internal Medicine, was part of the large Wisconsin Sleep Cohort Study, which has tracked the sleep patterns of more than 1,400 men and women since 1988. The subjects are brought into a lab every four years for a full evaluation of their sleep habits. Having undergone one of those overnight polysomnographies, I can tell you that they are no fun. Researchers attach little electrical leads all over your body—including your eyelids—to measure brain activity, eye and muscle movement, leg movement, airflow, chest and abdominal movement, heart rhythm and oxygen saturation. In the Wisconsin study, the subjects were also asked to complete the Zung depression survey, a 20-question test carefully designed to determine whether you are clinically depressed. (See more about sleep.)

Judging from the results, the experiment was worth the trouble. Although it has long been known that there was an association between poor sleep and depression, the researchers were able to take the link an important step further. They were able to measure what scientists call a dose response. This one suggests a causal relationship between the severity of a sleep disorder and the odds of becoming depressed. After adjusting for age and gender, the scientists found that patients with minimal breathing disorders were 1.6 times as likely to become depressed as those without. Those with mild cases were twice as likely, and those with moderate to severe cases were 2.6 times as likely.

Sleep disturbances are a well-known symptom of depression. But Dr. Phyllis Zee, a professor of neurology at Northwestern University who wrote the accompanying editorial in the journal, told me that the new evidence suggests that it may be the other way around: the sleep disruptions are what's causing the depression. Another theory is that during episodes of the severe disorder known as sleep apnea—when breathing briefly stops altogether—there are moments when the brain isn't getting enough oxygen, another possible risk factor for depression.

Regardless of the cause, there is a message here for patients and doctors: snoring and other sleep-related breathing issues should be treated seriously, both for the trouble they cause in their own right and for the deeper problems they could trigger.

As for me, my snoring seems to have ceased for the time being without further ill effects. My wife, my child, my dog and I are all sleeping through the night.

Sanjay Gupta is a neurosurgeon and CNN medical correspondent

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