RESEARCH
Respiration-triggered olfactory stimulation reduces obstructive sleep apnea severity: A prospective pilot study
Obstructive sleep apnea is a prevalent sleep-disordered breathing condition characterized by repetitive reduction in breathing during sleep. Olfactory stimulation during sleep was effective in reducing the severity of obstructive sleep apnea markers without inducing arousals, and may provide a novel treatment for obstructive sleep apnea, prompting continued research.
The Influence of Odorants on Respiratory Patterns in Sleep
To assess the feasibility of using odors as a potential mechanism for treating sleep apnea, we set out to test the hypothesis that odorants delivered during sleep would modify respiratory patterns without inducing arousal or wake in healthy sleepers.
Odors enhance slow-wave activity in non-rapid eye movement sleep
Most forms of suprathreshold sensory stimulation perturb sleep. In contrast, presentation of pure olfactory or mild trigeminal odorants does not lead to behavioral or physiological arousal. In fact, some odors promote objective and subjective measures of sleep quality in humans and rodents.
Humans can learn new information during sleep
During sleep, humans can strengthen previously acquired memories, but whether they can acquire entirely new information remains unknown. The nonverbal nature of the olfactory sniff response, in which pleasant odors drive stronger sniffs and unpleasant odors drive weaker sniffs, allowed us to test learning in humans during sleep.
https://www.nature.com/articles/nn.3193
Olfactory Aversive Conditioning during Sleep Reduces Cigarette-Smoking Behavior
Recent findings suggest that novel associations can be learned during sleep.
We tested the hypothesis that olfactory aversive conditioning during sleep will alter cigarette-smoking behavior during ensuing wakefulness.
the reduction in smoking following aversive conditioning during sleep was significantly greater than in two separate control sleep experiments that tested aversive odors alone and the effects of cigarette odors and aversive odors without pairing. To conclude, a single night of olfactory aversive conditioning during sleep significantly reduced cigarette-smoking behavior in a sleep stage-dependent manner, and this effect persisted for several days.
Olfactory sniffing signals consciousness in unresponsive patients with brain injuries
This study introduces a novel “sniff test” to assess consciousness in patients with disorders of consciousness (DoC). Our researchers found that olfactory sniffing signals can reliably indicate consciousness and predict recovery in unresponsive patients1. The test involves presenting pleasant and unpleasant odors to patients while measuring their nasal airflow. Patients in a minimally conscious state (MCS) showed significant changes in sniffing patterns in response to odors, while those in an unresponsive wakefulness state (UWS) had varied responses. The sniff response was found to be a strong predictor of long-term survival and recovery, with over 91% of patients who showed a sniff response surviving after 3.5 years. This simple, inexpensive test could potentially improve diagnosis accuracy and inform treatment strategies for patients with severe brain injuries
