Olfactory Function and Delayed Neurocognitive Recovery

Effects of Odor Enrichment on Delayed Neurocognitive Recovery

To explore whether odor enrichment can reduce the risk of delayed neurocognitive recovery as an intervention strategy.

Study Overview

• Status: Completed
• Conditions: Delayed Neurocognitive Recovery
• Intervention / Treatment: Behavioral: Odor Enrichment

Detailed Description

Postoperative neurocognitive disorder, one of the most common postoperative complications in older adults, includes acute postoperative delirium, delayed neurocognitive recovery (within the 30 days recovery period, dNCR), and postoperative neurocognitive dysfunction (from expected recovery 30 days to 12 months). Previous studies showed that the incidence of dNCR ranged from 18% to 40% and is mainly characterized by cognitive impairment, which can develop into long-term cognitive impairment, even elevating the risk of Alzheimer's Disease (AD) related dementia and premature mortality. These symptoms can have significant adverse effects on quality of life and may increase the risk of other physical and psychological disorders, potentially impacting social stability. These statistics underscore the importance of early detection and timely intervention in mitigating the long-term effects of dNCR. Despite the significance of dNCR, effective treatment options remain elusive.

Based on these insights, previous studies have explored the impact of olfactory enrichment in animal models. Zhang et al. demonstrated that surgery and anesthesia could cause olfactory impairment, which might contribute to dNCR, while suggesting that odor enrichment, a non-pharmacological intervention, could reduce postoperative cognitive impairment in animal models. Olfactory enrichment, also known as olfactory training, is a safe and affordable treatment and may have preventative or supportive effects on olfactory function or cognitive function. Evidence supports its effectiveness in treating olfactory function from various causes and in reducing cognitive impairment.

Despite these findings, there is limited research on whether odor enrichment can serve as a mitigating strategy for dNCR among human populations. To address this gap, we conducted a clinical study to investigate whether odor enrichment could mitigate dNCR in geriatric patients and to explore the relationship between olfactory function and dNCR.

• Study Type: Interventional
• Enrollment (Actual): 131
• Phase: Not Applicable

Contacts and Locations

Study Locations

• China
  • Shanghai
    • Shanghai, Shanghai, China, 200072
      • Shanghai Tenth People's Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 65 years and older (Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. were aged at least 65 years old;
2. were expected a postoperative hospital stay of at least 7 days;
3. had American Society of Anesthesiologist (ASA) class I to II;
4. were native Mandarin speakers;
5. had been referred for a total knee or hip replacement under general anesthesia.

Exclusion Criteria:

1. were prior diagnosed of neurologic diseases by the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10);
2. had a history of mental disorders diagnosed using the Diagnostic and Statistical Manual of Mental Disorders (DSM-5);
3. had a history of illness or surgery with nasal or sinus;
4. caught cold within one week;
5. impaired vision or auditory function which may affect the assessments;
6. were unwilling to comply with the protocol or procedures;
7. did not pass the Mini-mental State Examination (illiterates get less than 18 points, primary school graduates get less than 20 points, secondary school graduates or higher get less than 24 points) .

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Intervention Group; Patients randomly assigned to intervention group will get odor enrichment during the perioperative period	Behavioral: Odor Enrichment; Patients in intervention group will get odor enrichment during perioperative period (3 days before the surgery and 7 days after the surgery). Odor-enriched participants were exposed daily for 24 hours to different aromatic fragrances (phenyl ethyl alcohol - rose; eucalyptol - eucalyptus; citronellal - lemon; eugenol - cloves) referred to previous studies. Odors were changed for each subject after 24 hours. According to previous studies, 10 drops of the 100% essential oil (0.5 ml) were dropped on a fabric which was placed in tea bags hanging at the hospital bedside.
No Intervention: Non-intervention Group; Patients randomly assigned to non-intervention group will not get any odor enrichment during the perioperative period

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of dNCR	Participants underwent neuropsychological test battery, which referred to International Study Group of Postoperative Cognitive Dysfunction (ISPOCD) test battery and modified according to the characteristics of Chinese patients. The neuropsychological test battery consisted of the Hopkins Verbal Learning Test-Revised (HVLT-R), Brief Visuo-spatial Memory Test-Revised (BVMT-R), Trails Making Test (TMT), Digital Span Test (DST), HVLT-R Delayed Recall Test, HVLT-R Recognition Discrimination Index, BVMT-R Delayed Recall Test, BVMT-R Recognition Discrimination Index and Verbal Fluency Test (VFT). According to the International Study of Perioperative neurocognitive disorder definition, dNCR was diagnosed by calculating the "Z-score".	3 days before surgery (baseline) and 7 days after surgery (follow-up)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Olfactory identification ability	Five-odor-olfactory detection arrays were applied to test the odor identification ability of the participants three days before and then about 7 days after the surgery. This test consisted of 5 pen-shaped test sticks without labels containing five odorants including vinegar, banana, mint, rose and coal tar odor. After sniffing each stick, participants should identify each odor freely. The interval between odor presentations was about 30 seconds. The scores ranged from 0 to 5.	3 days before surgery (baseline) and 7 days after surgery (follow-up)

Collaborators and Investigators

• Sponsor: Shanghai 10th People's Hospital
• Collaborators: Massachusetts General Hospital
• Investigators: Principal Investigator: Yuan Shen, Shanghai 10th People's Hospital

Publications and helpful links

General Publications

• Kim MS, Yoon JH, Kim HJ, Yong SW, Hong JM. Olfactory dysfunction is related to postoperative delirium in Parkinson's disease. J Neural Transm (Vienna). 2016 Jun;123(6):589-94. doi: 10.1007/s00702-016-1555-0. Epub 2016 Apr 20.
• Brown CH 4th, Morrissey C, Ono M, Yenokyan G, Selnes OA, Walston J, Max L, LaFlam A, Neufeld K, Gottesman RF, Hogue CW. Impaired olfaction and risk of delirium or cognitive decline after cardiac surgery. J Am Geriatr Soc. 2015 Jan;63(1):16-23. doi: 10.1111/jgs.13198.
• Zhang C, Han Y, Liu X, Tan H, Dong Y, Zhang Y, Liang F, Zheng H, Crosby G, Culley DJ, Marcantonio ER, Shen Y, Cao JL, Xie Z. Odor Enrichment Attenuates the Anesthesia/Surgery-induced Cognitive Impairment. Ann Surg. 2023 Jun 1;277(6):e1387-e1396. doi: 10.1097/SLA.0000000000005599. Epub 2022 Jul 18.
• Pieniak M, Oleszkiewicz A, Avaro V, Calegari F, Hummel T. Olfactory training - Thirteen years of research reviewed. Neurosci Biobehav Rev. 2022 Oct;141:104853. doi: 10.1016/j.neubiorev.2022.104853. Epub 2022 Sep 5.

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2018
• Primary Completion (Actual): December 31, 2021
• Study Completion (Actual): December 31, 2022

Study Registration Dates

• First Submitted: February 15, 2018
• First Submitted That Met QC Criteria: February 15, 2018
• First Posted (Actual): February 22, 2018

Study Record Updates

• Last Update Posted (Actual): July 31, 2025
• Last Update Submitted That Met QC Criteria: July 28, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Mental Disorders; Postoperative Complications; Pathologic Processes; Neurocognitive Disorders; Cognition Disorders; Postoperative Cognitive Complications; Cognitive Dysfunction
• Other Study ID Numbers: dsyy003

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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