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Human Perception of Odors and Odor Blockers

Human Perception of Odors and Odor Blockers

Status
Completed
Phases
Unknown
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT06191419
Enrollment
27
Registered
2024-01-05
Start date
2024-04-05
Completion date
2025-05-15
Last updated
2026-07-23

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Smoking Behaviors, Tobacco Smoking

Keywords

Odors, Sensory perception, Nicotine addiction, Motivation

Brief summary

The goal of this clinical trial is to determine whether blockers of perception of key odorants in cigarette smoke have any utility in smoking cessation. The main question it aims to answer is: • Can odor blockers be used to suppress perception of the intensity of cigarette smoke in ways that reduce the ability of the odor of cigarette smoke to increase the urge to smoke. Participants will be asked to smell up to 20 odor samples per session and report on odor pleasantness and desire to smoke.

Detailed description

The experimental treatments include controls (clean air, irrelevant odor), blocking odors, cigarette smoke odor, and cigarette smoke odor mixed with blocking odors or irrelevant odor. To obtain cigarette smoke odor a 1 inch length of a 1R6F research cigarette is burned to completion in a sealed 5 gallon chamber fitted with septa. Using a syringe fit with a needle and filter, 60 mL aliquots of smoke odor are obtained. These smoke odor aliquots, along with blocking odors, are injected into odor sample bags fit with a septum and a valve that can be attached to the CPAP nose mask worn by each participating smoker. Participants open the valve, inhale once through the nose, close the valve, and then remove the bag from the mask before reporting odor pleasantness and the desire to smoke. A 4 min wait period is enforced between each odor presentation to prevent odor adaptation and to allow acute motivational effects to subside. During these intervals, a nature documentary was available for viewing. Two measures of the desire to smoke are made. An objective method uses a validated relative reinforcing measure, requiring participants to record how many cigarettes they would purchase at each step along a logarithmically increasing price scale that ranges from $0 to $1,120 per cigarette. The breakpoint on this scale at which a participant is no longer willing to pay is the measure of the urge to smoke. As a subjective measure, participants report their urge to smoke as a value between 0 and 100. Participants also provide a forced choice measure of odor pleasantness, indicating either pleasant or unpleasant for each odor. In a testing session a participant sniffs a mixture of blocking odors mixed with cigarette smoke, along with control odor samples. Presentation order is randomized. Each participant is assigned their own CPAP nose mask, and masks are disinfected after use. Participants also provide demographic (age, sex, ethnic and racial background) and smoking history information (cigarettes per day, preferred brand, age at onset, and time since last cigarette).

Interventions

OTHEROdorants

Each smoker is assigned a CPAP nose mask. Odor sample bags are attached to the mask. Smokers open the valve, inhale once through the nose, close the valve, remove the bag from the mask and report on the odor.

Sponsors

Tim McClintock
Lead SponsorOTHER
National Institute on Deafness and Other Communication Disorders (NIDCD)
CollaboratorNIH

Study design

Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE

Masking description

Odor bags are prepared by one staff member and labeled with a code so that other investigators administering tests cannot identify which treatment is being given and inadvertently influence outcomes. The code is not visible to participants. This prevents participants from anticipating the effect of the treatment.

Intervention model description

Each subject experiences and reports on all of the odor blocker and control treatments.

Eligibility

Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
Yes

Inclusion criteria

* Smoker

Exclusion criteria

* Non Smoker * Self reported inability to smell or taste

Design outcomes

Primary

MeasureTime frameDescription
Cigarette Purchase Task3 hours (total for all outcome measures)The Cigarette Purchase Task (Strickland et al., 2016) requires selecting how much the smoker is willing to spend for a single cigarette (their preferred brand) from a list of 19 amounts ranging from $0.00 (free) to $1,120. The measure from the selections is the breakpoint where the participants are no longer willing to purchase. These data are skewed and are log transformed (after adding 0.01) for statistical analysis.
Desire to Smoke3 hours (total for all outcome measures)A rating of participant's desire to smoke on a scale of 0 - 100, where a higher score indicates increased desire.

Secondary

MeasureTime frameDescription
Odor Pleasantness Score3 hours (total for all outcome measures)Participants complete a forced-choice test by rating whether the odor is pleasant or unpleasant. Responses were recorded as a binary measure where 0=unpleasant and 1=pleasant. Scores range from 0 to 1, with higher score indicate greater odor pleasantness.

Countries

United States

Contacts

PRINCIPAL_INVESTIGATORTimothy McClintock, PhD

University of Kentucky

Participant flow

Pre-assignment details

All participants assessed for eligibility were enrolled and started the study procedures.

Baseline characteristics

Characteristic
Age, Categorical
<=18 years
0 Participants
Age, Categorical
>=65 years
0 Participants
Age, Categorical
Between 18 and 65 years
27 Participants
Ethnicity (NIH/OMB)
Hispanic or Latino
4 Participants
Ethnicity (NIH/OMB)
Not Hispanic or Latino
23 Participants
Ethnicity (NIH/OMB)
Unknown or Not Reported
0 Participants
Race (NIH/OMB)
American Indian or Alaska Native
0 Participants
Race (NIH/OMB)
Asian
0 Participants
Race (NIH/OMB)
Black or African American
3 Participants
Race (NIH/OMB)
More than one race
0 Participants
Race (NIH/OMB)
Native Hawaiian or Other Pacific Islander
0 Participants
Race (NIH/OMB)
Unknown or Not Reported
0 Participants
Race (NIH/OMB)
White
24 Participants
Region of Enrollment
United States
27 participants
Sex: Female, Male
Female
18 Participants
Sex: Female, Male
Male
9 Participants

Adverse events

Event typeEG000
affected / at risk
deaths
Total, all-cause mortality
0 / 27
other
Total, other adverse events
0 / 27
serious
Total, serious adverse events
0 / 27

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Jul 24, 2026