Self-administered Neurostimulation Intervention for Firefighter Traumatic Stress to Reduce Alcohol Use: Pilot Study

The investigators' goal is to evaluate the feasibility, acceptability, and appropriateness of a transcutaneous auricular neurostimulation (tAN) protocol for firefighters with alcohol use disorder (AUD) and co-occurring posttraumatic stress (PTS) symptoms. Firefighters are repeatedly exposed to potentially traumatic events, and many experience PTS symptoms as a result. Over 50% of firefighters report past-month heavy alcohol use, and many use alcohol to "self-medicate" symptoms of hyperarousal, intense negative affect, and insomnia that follow traumatic events. tAN, a patient-administered intervention that delivers electrical stimulation to branches of the vagus and trigeminal nerves, has shown promise for alleviating symptoms of PTS and opioid withdrawal. However, its effects have yet to be tested in a sample of firefighters with AUD and co-occurring PTS symptoms. Within this highly impacted population, providing a culturally informed tAN intervention promises to reduce the PTS symptoms driving heavy alcohol use. Study results, utilizing the ear-worn Sparrow device, will inform a revised trial protocol and an FDA pre-submission to support a PTS/AUD indication. In summary, the investigators will examine whether the study protocol is feasible and whether active tAN provides preliminary evidence of reducing PTS symptoms and heavy drinking events compared to an active sham.

Design: The investigators will randomize 20 active-duty firefighters who engage in heavy drinking and report at least moderate PTS symptoms to receive: 1) active tAN or 2) active sham tAN. tAN is administered via the Sparrow device for at least 1 hour per day, 5 days per week, throughout a 4-week treatment phase. Assessments will be collected at Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8), alongside daily ecological momentary assessments and audio journals. The primary outcome will be posttreatment ratings on the Feasibility of Intervention Measure (FIM). Secondary outcomes include ratings of protocol acceptability (Acceptability of Intervention Measure; AIM) and device appropriateness (Intervention Appropriateness Measure; IAM). Exploratory clinical outcomes include the PTSD Checklist for DSM-5 (PCL-5) and heavy drinking events. Biomarker and ecological momentary assessment (EMA) analysis will examine the dynamic relationships between neurostimulation, autonomic arousal (heart rate, heart rate variability), sleep, trauma exposure, and alcohol motives.

Aim (1): Evaluate the feasibility, acceptability, and appropriateness of the study protocol and Sparrow intervention for a firefighter population with AUD and co-occurring PTS symptoms.

Hypothesis 1a: The protocol and intervention will be feasible, acceptable, and appropriate, as indicated by mean scores of 4 or greater on the FIM, AIM, and IAM.

Hypothesis 1b: The trial will meet feasibility benchmarks, including a dropout rate ≤30%, ≥80% device adherence, >50% EMA completion, and ≥80% blinding effectiveness.

Exploratory Aim (1): Assess whether the results provide preliminary support for the efficacy of the active tAN device in reducing PTS symptoms and heavy drinking events compared to sham tAN.

Exploratory Hypothesis (1): Active tAN will result in larger mean pre-post reductions and a higher percentage of clinically meaningful change in PCL-5 total scores and heavy drinking events compared to active sham tAN.

Exploratory Aim (2): Develop longitudinal data analysis strategies to examine dynamic relationships between participants' duty status, ongoing trauma exposure, PTS symptoms, alcohol use/motives, autonomic arousal, sleep patterns, and device usage.

The long-term objective of this feasibility pilot is to use the data to validate the FDA clearance strategy, inform revisions to the study protocol, and support an R01 application for a fully powered Phase II RCT.

• Transcutaneous auricular neurostimulation (tAN) (Device), also known as Sparrow Link: The research version of Spark's Sparrow Ascent for vagus and trigeminal nerve stimulation provided through a disposable earpiece that attaches to the ear. The device allows the participant to self-administer stimulation when they choose.
• Active Sham (Device), also known as Sparrow Link: Same research device as the active tAN condition, but programmed with active sham parameters such that the stimulation is sufficient to be felt on the skin, but subtherapeutic.

Primary outcomes

• Protocol Feasibility as Assessed by the Feasibility of Intervention Measure (FIM) [Post-treatment (Week 4) and 1-month follow-up (Week 8)]: The FIM is a 4-item self-report questionnaire assessing the extent to which participants agree that the study protocol is feasible to implement. Items are rated on a 5-point Likert scale ranging from 1 ("Completely disagree") to 5 ("Completely agree"). Scores are calculated as an average across items (ranging from 1 to 5), with higher scores indicating greater feasibility. Feasibility success is predefined as a mean score of at least 4.

Secondary outcomes

• Protocol Acceptability as Assessed by the Acceptability of Intervention Measure (AIM) [Post-treatment (Week 4) and 1-month follow-up (Week 8)]: The AIM is a 4-item self-report questionnaire evaluating the degree to which participants perceive the study protocol to be acceptable. Items are rated on a 5-point Likert scale from 1 ("Completely disagree") to 5 ("Completely agree"). Scores are averaged across items (range: 1 to 5), where higher scores indicate greater acceptability (benchmark: mean at least 4).
• Device Appropriateness as Assessed by the Intervention Appropriateness Measure (IAM) [Post-treatment (Week 4) and 1-month follow-up (Week 8)]: The IAM is a 4-item self-report questionnaire assessing the perceived fit, relevance, and suitability of the Sparrow device for this population. Items are rated on a 5-point Likert scale from 1 ("Completely disagree") to 5 ("Completely agree"). Scores are averaged across items (range: 1 to 5), with higher scores reflecting greater appropriateness (benchmark: mean at least 4).
• Protocol Feasibility: Participant Retention Rate [Baseline (Week 0) through Week 4]: Calculated as the percentage of randomized participants who complete the study through the Week 4 assessment. A study dropout rate > 30% will indicate the need for protocol modification.
• Protocol Feasibility: Sparrow Device Adherence Rate [Daily throughout the 4-week treatment phase (Weeks 1-4)]: Calculated as the percentage of participants who adhere to the minimum required stimulation dosage (at least 1 hour/day, 5 days/week) for at least 75% of the 4-week active treatment period, measured via automated device usage logs. The feasibility benchmark is achieved if at least 80% of participants meet this threshold.
• Protocol Feasibility: Ecological Momentary Assessment (EMA) Completion Rate [Daily throughout the 4-week treatment phase (Weeks 1 through 4)]: Calculated as the percentage of prompted daily EMA surveys successfully completed by participants across the 4-week active phase. An overall completion rate of 50% or below will indicate the need for protocol modification.
• Blinding Effectiveness Assessment [Post-treatment (Week 4)]: Assessed by asking participants to guess their condition assignment (Active tAN vs. Active Sham) and their confidence in that guess. Effective blinding is operationalized as at least 80% of participants remaining blind to condition.

Other outcomes

• Posttraumatic Stress Disorder Symptom Severity (PCL-5) [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Mean pre-post change in PTSD Checklist for DSM-5 (PCL-5) total scores, as well as the proportion of participants achieving clinically meaningful symptom reduction (at least 30% reduction from baseline). The PCL-5 comprises 20 items rated from 0 ("Not at all") to 4 ("Extremely"), yielding total symptom severity scores from 0 to 80, where lower scores indicate lower PTS symptom severity.
• Heavy Drinking Events [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Change in the frequency of heavy drinking events using sex-assigned-at-birth thresholds (defined as 5+ standard drinks/day or 15+ drinks/week for males; 4+ drinks/day or 8+ drinks/week for females), measured via the Timeline Follow-back (TLFB). Also evaluated as the percentage of participants achieving a clinically meaningful reduction (50% or greater reduction in heavy drinking events).
• Clinician-Assessed PTSD Severity (CAPS-5) [Baseline (Week 0), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Evaluated using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), measuring past-week PTSD diagnostic status and continuous symptom severity, where lower scores indicate reduced symptom severity.
• Insomnia Symptom Severity (ISI) [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Total scores on the Insomnia Severity Index (ISI), a 7-item self-report questionnaire assessing the nature, severity, and impact of insomnia symptoms. Scores range from 0 to 28, with lower scores indicating less severe insomnia.
• Depression Symptom Severity (PHQ-9) [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Total score on the Patient Health Questionnaire-9 (PHQ-9), assessing depressive symptom severity over the past 2 weeks. Scores range from 0 to 27, with lower scores indicating lower symptom severity.
• Generalized Anxiety Symptom Severity (GAD-7) [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Total score on the Generalized Anxiety Disorder-7 (GAD-7) scale, assessing anxiety symptom severity over the past 2 weeks. Scores range from 0 to 21, with lower scores indicating less anxiety.
• Quality of Life (WHOQOL-BREF US) [Baseline (Week 0), Interim (Week 2), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Domain and overall scores on the WHO Quality of Life Brief - US Version, assessing physical, psychological, social, and environmental wellbeing, where higher scores reflect higher quality of life.
• Psychosocial Functioning Impairment (B-IPF) [Baseline (Week 0), Post-treatment (Week 4), and 1-month follow-up (Week 8)]: Total score on the Brief Inventory of Psychosocial Functioning, assessing functional impairment attributable to posttraumatic stress symptoms across interpersonal, work, and routine domains. Lower scores reflect less impairment.
• Mean Resting Heart Rate [Continuously daily throughout the 4-week treatment phase (Weeks 1 through 4)]: The average heart rate, measured in beats per minute.
• Mean Heart Rate Variability (HRV) [Continuously daily throughout the 4-week treatment phase (Weeks 1 through 4)]: The average heart rate variability, measured in milliseconds (ms).
• Mean Total Sleep Time per Night [Continuously daily throughout the 4-week treatment phase (Weeks 1 through 4)]: The average total duration of sleep per night, measured in minutes.
• Mean Number of Nighttime Awakenings [Continuously daily throughout the 4-week treatment phase (Weeks 1 through 4)]: The average count of distinct awakening events during the primary sleep period per night.
• Qualitative Implementation Feedback (Study Experience Interview) [Post-treatment (Week 4) and 1-month follow-up (Week 8)]: Rapid turnaround qualitative data reduction of semi-structured interviews evaluating participant perceptions of the device, EMA procedures, barriers, facilitators, and recommended modifications to inform protocol refinements.

Sex: All, ages: 18 Years to 64 Years

Inclusion Criteria:

* Active-duty firefighter aged 18 to 64 years old.
* Endorse at least one heavy drinking event within the past month based on sex-assigned-at-birth thresholds (males: 5+ standard drinks on a single day and/or 15+ over 7 days; females: 4+ standard drinks on a single day and/or 8+ over 7 days).
* Meet DSM-5 criteria for mild, moderate, or severe alcohol use disorder. Report at least moderate posttraumatic stress (PTS) symptoms, defined as a PTSD Checklist for DSM-5 (PCL-5) score of 20 or greater.
* Willing to attend research visits, complete EMA measurements, use the study device, and provide informed consent in English.

Exclusion Criteria:

* Currently engaged in evidence-based PTSD psychotherapy or AUD-focused counseling at the time of randomization, or has experienced a past-month change in PTSD- or AUD-relevant medication.
* High risk for moderate to severe alcohol withdrawal syndrome, indicated by a Prediction of Alcohol Withdrawal Severity Scale (PAWSS) score of 4 or greater.
* Unmedicated psychotic disorder or unmedicated bipolar disorder with a manic episode in the past month.
* History of epileptic seizures, neurological diseases, or traumatic brain injury with lasting effects.
* Current evidence of an uncontrolled and/or clinically significant medical or psychiatric condition precluding device-related research participation.
* Suicide attempt in the past month leading to hospital admission, or expressed suicidal ideation with intent and plan in the past month.
* Presence of devices such as pacemakers, cochlear prostheses, or neurostimulators.
* Current ear infection or abnormal ear anatomy that would prevent therapeutic earpiece contact to at least one ear.
* Pregnant, lactating, or a person of childbearing potential not using adequate contraception.

NIH grants: R34AA032824