Olfactory Function and Model-Based Behavior in People Living With HIV and SUD

Olfactory Function and Model-based Behavior in People Living With HIV and SUD

Background:

Human immunodeficiency virus (HIV) infection can affect areas of the brain that control thinking ability. These same areas of the brain also control the sense of smell. HIV infection is common in people with substance use disorder (SUD). SUD also affects thinking ability. Researchers want to learn more about the connection between the sense of smell and decision-making ability in people with HIV, SUD, or both.

Objective:

To test the sense of smell in people with HIV and/or SUD and how they make choices based on odors.

Eligibility:

People aged 18 to 65 years with any of these: (1) HIV, (2) SUD, (3) both HIV and SUD, or (4) neither SUD nor HIV.

Design:

Participants will have 2 visits. Each visit will last 3 to 5 hours.

In visit 1, participants will have a blood draw and a saliva swab. They will answer questions about their health, sleep habits, food intake, and substance use. They will have smell tests:

They will smell scented sticks and answer questions about them. They will be blindfolded for some tests.

They will perform tasks on a computer. They will look at pictures and smell pleasant food odors, such as chocolate cake or pizza. Smells will be delivered using a nasal mask. Their sniffing and breathing will be measured. They may also be exposed to odor-free air. They will eat food that corresponds to one of the food odors they smelled.

In visit 2, participants will do a saliva swab and a different computer task that involves odors. They will also have tests of their attention and memory. Participants may opt to have an imaging scan of the brain.

Study Overview

• Status: Not yet recruiting
• Conditions: HIV; Substance Use Disorder

Detailed Description

Study Description:

Cognitive impairments persist in people living with Human Immunodeficiency Virus (HIV) despite anti-retroviral therapy (ART). However, these impairments remain under-characterized and it is not clear whether they include deficits in model-based control of behavior. HIV is common in people with substance use disorder (SUD) but the combined impact of HIV and SUD on cognition remains unclear. The olfactory system is uniquely vulnerable to neurodegeneration and overlaps with brain regions involved in decision making. This study will investigate olfactory function and model-based behavior in people living with HIV and SUD, and relate these measures to biomarkers of neurodegeneration.

Objectives:

The primary objective of this protocol is to compare olfactory function and performance on behavioral tasks assessing model-based behavior between people living with and without HIV, and between people with and without SUD.

Secondary objectives of this protocol are to compare blood-based and MRI0-based biomarkers of neurodegeneration between people living with and without HIV, and between people with and without SUD.

Endpoints:

Primary:

• Olfactory function (Sniffin Sticks Threshold, Discrimination, and Identification tests)
• Behavior on tasks assessing model-based behavior (outcome devaluation and sensory preconditioning)

Secondary:

• Blood-based biomarker of neurodegeneration (Neurofilament Light Chain [NfL])
• MRI-based biomarker of neurodegeneration (Magnetic Resonance Imaging)

• Study Type: Observational
• Enrollment (Estimated): 120

Contacts and Locations

• Study Contact: Name: NIDA IRP Screening Team; Phone Number: (800) 535-8254; Email: researchstudies@nida.nih.gov
• Study Contact Backup: Name: Thorsten Kahnt, Ph.D.; Phone Number: (667) 312-5175; Email: thorsten.kahnt@nih.gov

Study Locations

• United States
  • Maryland
    • Baltimore, Maryland, United States, 21224
      • National Institute on Drug Abuse
      • Contact: Thorsten Kahnt; Phone Number: 667-312-5175; Email: thorsten.kahnt@nih.gov

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

local community sample: metropolitan Baltimore area

Description

• INCLUSION CRITERIA:

In order to be eligible to participate in this study, an individual must meet all of the following criteria:

For all participants:

• Stated willingness to comply with all study procedures and availability for the duration of the study
• Aged 18-65 years old. Justification: prevalence of olfactory impairments increases with age; after age 53, the prevalence is 24.5 percent, increasing to 62.5 percent in people ages 80-97.
• Agreement to adhere to Lifestyle Considerations throughout study duration.
• Ability of subject to understand and the willingness to sign a written informed consent document.

For participants in the HIV+ and SUD+ and HIV+ and SUD- groups:

-HIV positive.

For participants in the HIV+ and SUD+ and HIV- & SUD+ groups:

-Substance Use Disorder (SUD) other than Alcohol Use Disorder (AUD) or Tobacco Use Disorder (TUD).

EXCLUSION CRITERIA:

An individual who meets any of the following criteria will be excluded from participation in this study:

For all participants:

• History of neurological illnesses or neurosurgery including but not limited to cerebrovascular accident, Parkinson disease, Alzheimer disease, Huntington disease, central nervous system (CNS) tumor, significant head trauma with sequelae, multiple sclerosis or other demyelinating diseases, epilepsy, movement disorders. The MAI will also retain discretion to exclude based on a history of a neurological illness or trauma that may compromise data integrity.
• History of current (past 12 months) uncontrolled major DSM-5 psychiatric disorder including major affective disorder, obsessive-compulsive disorder, schizophrenia, or posttraumatic stress disorder, excluding SUD.
• Candidates who recently (12 hours prior to a study visit) used medications and/or substances that are psychoactive or otherwise affect alertness will have to pass a clinical assessment for intoxication on the day of the study visit. Based on participant preferences and MAI/PI judgment, participants who fail the clinical assessment for intoxication will either be withdrawn or rescheduled.
• History of clinically significant anaphylaxis, e.g., due to severe asthma or food and nonfood allergies (e.g., latex, detergents, soap, etc.). The MAI will retain discretion to exclude a participant based on this criterion.
• Uncorrected impairments in visual acuity.
• Non-English speaking. Justification: The data integrity of some of the behavioral tasks used in this study would be compromised as they have only been validated in English.
• Pregnancy.
• Any other condition that in the judgment of the investigators is incompatible with participation.

For participants in the HIV+ and SUD- and HIV- and SUD- groups:

• History of current (past 12 months) SUD, excluding tobacco use disorder.
• Pattern of alcohol and drug use in the past 12 months that is indicative of harmful use, loss of control over use, or physical dependence.
• Daily alcohol or drug use (excluding caffeine and nicotine) for at least 4 continuous weeks in the past 12 months.

For participants in the HIV- and SU+ and HIV- and SUD- groups:

-HIV positive.

For the Optional MRI Segment:

-Unable to undergo MRI scanning due to certain metallic or magnetic devices or implants in the body, or claustrophobia.

Study Plan

How is the study designed?

Number of groups / cohorts

4

Cohorts and Interventions

Group / Cohort
HIV- & SUD-; Individuals without HIV and without an SUD
HIV- & SUD+; Individuals without HIV and with an SUD
HIV+ & SUD-; Individuals with HIV and without an SUD
HIV+ & SUD+; Individuals with HIV and with an SUD

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Olfactory function	Sniffin Sticks Threshold, Discrimination, and Identification tests	Visit 1
Model-based decision making	Model-based decision making as assessed in an outcome devaluation task (visit 1) and sensory preconditioning task (visit 2)	Visit 1 & 2

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Neurofilament Light Chain	Plasma levels of neurofilament light chain [NfL]	Visit 1
MRI	MRI-based biomarkers of neurodegeneration	Visit 2 (optional)

Collaborators and Investigators

• Sponsor: National Institute on Drug Abuse (NIDA)
• Investigators: Principal Investigator: Thorsten Kahnt, Ph.D., National Institute on Drug Abuse (NIDA)

Study record dates

Study Major Dates

• Study Start (Estimated): June 15, 2026
• Primary Completion (Estimated): June 27, 2031
• Study Completion (Estimated): June 27, 2031

Study Registration Dates

• First Submitted: June 4, 2026
• First Submitted That Met QC Criteria: June 9, 2026
• First Posted (Actual): June 10, 2026

Study Record Updates

• Last Update Posted (Actual): June 10, 2026
• Last Update Submitted That Met QC Criteria: June 9, 2026
• Last Verified: June 3, 2026

More Information

Terms related to this study

• Keywords: HIV; Decision Making; Substance Use Disorder; Olfaction
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Mental Disorders; Chemically-Induced Disorders; Sensation Disorders; Olfaction Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Anosmia; Substance-Related Disorders
• Other Study ID Numbers: 10002591; 002591-DA

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data will be de-identified, which may be shared with (a) open data repositories and (b) with collaborators with whom proper data sharing agreements are in place, after consultation with and approval from the NIDA Technology Development Coordinator. The code to those data will not be shared. @@@@@@
• IPD Sharing Time Frame: De-identified data may be made available for sharing for at least 5 years after study completion.
• IPD Sharing Access Criteria: De-identified data may be shared with (a) open data repositories and (b) with collaborators with whom proper data sharing agreements are in place, after consultation with and approval from the NIDA Technology Development Coordinator. Requests for data sharing will have to be addressed to the study PI in writing.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No