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Can smells wake us up from deep sleep?

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Will smoke, even the first, faint scent of a fire, wake a person from a deep slumber?

At least according to published research, the answer to that burning question is quite hazy: Maybe.

Maybe smoke will wake you up but maybe not, according to two studies conducted during the past 15 years. 

“There is scant research that addresses awakening from the smell of smoke,” said Dr. Thomas Freedom, program director of the NorthShore University HealthSystem Sleep Program near Chicago. (He was not affiliated with either study.) “Some of the findings are contradictory.”

This much sleep doctors know: sensory stimuli -- sound, temperature, touch, even pain -- become less effective in rousing people the deeper they drop into nightly sleep stages.

For example, Freedom said, it’s easier to rally a sleeper who is in “stage N1” – a lighter phase of slumber – versus a person in “N3” or REM (rapid eye movement) sleep, which is a more submerged state of siesta.

Things that go bump in the night or shoves from a frustrated bedmate (“Yo! Stop snoring!”) may activate “peripheral receptors” – tiny sensors, many of which are located in your skin. Louder sounds or stronger vibrations are, of course, more apt to fully wake someone, Freedom said.

“But the sense of smell may differ in that increasing intensity does not appear to lead to awakening in deeper stages of sleep,” Freedom said.

In 1997, a study performed by the Irondale Fire and Rescue Service in Irondale, Ala., found that among 10 adults who were snoozing in a medical sleep lab, two of the subjects awoke when a smoke odor was introduced into their room. 

In 2004, at Brown University, researchers found that among the six people they tested – three healthy men and three healthy women, aged 20 to 25 years old – all could be jostled awake disrupted by noise but none were stirred by odors. In the lab, the sleepers were exposed to both peppermint and pyridine, a compound that carries an strong, fish-like scent, reacting to neither. 

"As the saying goes," wrote the paper's co-author, psychiatry professor Mary A. Carskadon, "we 'wake up and smell the coffee,' not the other way around."

But Las Vegas resident Sharon Chayra believes the certain people – like her – with a fine-tuned olfactory sense are more prone to be yanked awake by a foreign smell. She’s been roused, she said, by the scents of her husband baking cookies late at night, by her dog pooping, and by fireplace embers that hadn’t been properly extinguished.

“We’d had a fire in the wood-burning fireplace downstairs. It was about 1 a.m. and I could just smell burning fire. I popped up just like a piece of toast,” said Chayra, 49. “There wasn’t smoke necessarily but enough of an odor for me to wake up and go check out what was going on.”

Once she reached main floor of her home, she doused the remaining red embers with water and sand.

Then again, Chayra says her children do tease her because she is constantly sniffing the air.

"'You act like a dog!’ That’s what they tell me. I guess I do. If I smell something, I will wake up and go track it down like a bloodhound.”