# A cross-sectional study of olfactory stimulation on retrieval of the Who, Where and When information in Alzheimer's disease

Karim Gallouj, Pascal Antoine, Guillaume Chapelet, Mohamad El Haj

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## To cite this version:

Karim Gallouj, Pascal Antoine, Guillaume Chapelet, Mohamad El Haj. A cross-sectional study of olfactory stimulation on retrieval of the Who, Where and When information in Alzheimer's disease. Geriatric Nursing, 2026, 68, pp.103857. 10.1016/j.gerinurse.2026.103857. hal-05535972

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## Featured Article

# A cross-sectional study of olfactory stimulation on retrieval of the Who, Where and When information in Alzheimer's disease

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Karim Gallouj, MD, PhDª, Pascal Antoine, PhDᵇ, Guillaume Chapelet, MD, PhDᶜ,ᵈ, Mohamad El Haj, PhDᶜ,ᵉ,\*

## ARTICLE INFO

**Article history:**

Received 20 January 2025

Received in revised form 4 September 2025

Accepted 5 January 2026

Available online 21 January 2026

**Keywords:**

Alzheimer's disease

Autobiographical memory

Memory rehabilitation

Odor

Olfactory stimulation

## ABSTRACT

We investigated whether olfactory stimulation can enhance the retrieval of contextual details—"who/where/when"—during autobiographical memory recall in patients with Alzheimer's-disease (AD). Previous research has shown that odors can trigger vivid autobiographical memories in healthy-adults, but evidence in AD is limited, and most studies have focused on general memory recall rather than specific contextual information. Given that a key feature of autobiographical decline in AD is difficulty retrieving contextual details, it remains unclear whether olfactory cues can selectively improve recall of "who," "where," and "when" information. In this cross-sectional study, 33 patients with AD and 35 healthy controls retrieved autobiographical events with and without odor exposure. Analyses revealed that odor exposure increased the number of "who," "where," and "when" details in both groups. These findings address a critical gap in the literature, demonstrating that olfactory stimulation can specifically support contextual memory retrieval in AD, offering a non-invasive-tool to mitigate autobiographical memory deficits.

© 2026 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license

(http://creativecommons.org/licenses/by/4.0/)

## Introduction

Alzheimer's Disease (AD) is a prevalent neurodegenerative disorder, affecting approximately 50 million people worldwide. It is characterized by progressive cognitive decline, including impairments in memory, language, executive function, and visuospatial abilities.¹ Because patients with AD have memory difficulties, including difficulties retrieving specific autobiographical memories (i.e., difficulties retrieving unique memories at a specific time and place), we investigated whether olfactory stimulation, which involves exposing individuals to specific odors to evoke sensory and memory responses, would help patients with AD retrieve specific autobiographical memories.

In clinical and research settings, olfactory stimulation is typically applied by selecting scents that are familiar, emotionally salient, or personally meaningful to the individual.²⁻⁸ Healthcare professionals may use essential oils, scented pads, or odor-dispensing devices to deliver these scents in a controlled manner, often presenting them

for brief periods before or during memory retrieval tasks. The intensity, duration, and type of odors are carefully chosen to maximize memory-evoking potential while minimizing discomfort. This approach allows clinicians to target autobiographical memory retrieval by associating specific odors with distinct past experiences.

Patients with AD typically encounter difficulties in retrieving specific autobiographical memories. According to the AMAD (autobiographical memory in Alzheimer's disease) model,⁹ this decline is due to dysfunction in organization, elaboration, and memory search strategies during retrieval, leading to a reduced subjective experience of the past. Few studies have examined which aspects of autobiographical specificity are affected, such as the ability to recall when and where an event occurred. In one study, patients with AD and older controls were asked to remember the "who, where, and when" of autobiographical events.¹⁰ Patients with AD showed poorer memory for these details, particularly the "when" aspect, indicating that difficulty with retrieving temporal information is a key feature of the disease. Given this, the present study explored whether olfactory stimulation could help AD patients overcome this challenge.

Our aim was further based on research demonstrating the positive effects of olfactory stimulation on autobiographical memory in

<footnote>ªCentre Hospitalier de Tourcoing, Unité de Gériatrie, Tourcoing, F59208, France</footnote>

<footnote>ᵇUniv. Lille, CNRS, CHU Lille, UMR 9193 SCALab - Sciences Cognitives et Sciences Affectives, F-59000 Lille, France</footnote>

<footnote>ᶜCHU Nantes, Clinical Gerontology Department, Bd Jacques Monod, F44093, Nantes, France</footnote>

<footnote>ᵈUniversité de Nantes, Inserm, TENS, The Enteric Nervous System in Gut and Brain Diseases, IMAD, Nantes, France</footnote>

<footnote>ᵉNantes Université, Univ Angers, Laboratoire de psychologie des Pays de la Loire, LPPL, UR 4638, F-44000 Nantes, France</footnote>

<footnote>*Corresponding author at: Faculté de Psychologie, LPPL - Laboratoire de Psychologie des Pays de la Loire, Université de Nantes, Chemin de la Censive du Tertre, 44312 Nantes Cedex 3, BP 81227, France.</footnote>

<footnote>E-mail address: el.haj@hotmail.fr (M. El Haj).</footnote>
patients with AD. A pioneering study, demonstrated that odor exposure improved memory specificity, mental-time travel, and retrieval time in patients with mild AD, compared to both music and odor-free conditions.¹¹ Similar findings were reported by another study showing more specific and emotionally charged autobiographical memories when exposed to odor.¹² Further studies have consistently found that odor exposure enhances the specificity of childhood, adulthood, and recent memories, triggers stronger emotional arousal, and even aids in imagining future events in patients with mild AD.¹³,¹⁴

Although the abovementioned studies have demonstrated the beneficial effects of odor exposure on autobiographical memory in patients with AD, it remains unclear which dimension of specificity (i.e., when, where or who) benefits from odor exposure. In other words, research on odor-evoked autobiographical memories in AD has assessed whether these memories are general or specific¹¹,¹²,¹⁴⁻¹⁶ without investigating when, where or who benefits from odor exposure. It is thus still unknown whether odor exposure may alleviate the ability of patients with AD to remember when an event occurred, where an event occurred, or who was present during the event. This is important because, as previously mentioned, the hallmark of a decrease in the ability to retrieve contextual information in patients with AD is the difficulty of retrieving temporal information. It would be of significant interest to investigate whether odor exposure may help patients with AD overcome the major challenge of autobiographical retrieval, specifically retrieving when an event occurred. The retrieval of temporal information is considered a key component of the subjective experience of remembering, as it underpins the ability to mentally reconstruct past events within a coherent framework of time.¹⁷,¹⁸ Temporal context is central to autobiographical memory because it situates the "self" within a specific temporal and spatial framework, contributing to the subjective sense of reliving.¹⁹

In line with these considerations, the present study specifically aimed to address the following research questions: (1) Does olfactory stimulation enhance the retrieval of contextual details—"who," "where," and "when"—during autobiographical memory recall in patients with AD? (2) Which of these contextual dimensions benefits most from odor exposure? By answering these questions, we sought to clarify the potential of olfactory stimulation not only to improve memory retrieval but also to restore a sense of temporal coherence, which is essential for reexperiencing personal past events. We expected that odor exposure would have positive effects on the ability of patients with AD to retrieve temporal information during autobiographical retrieval.

## Methods

### Participants

The study included thirty-three patients with a clinical diagnosis of probable mild AD and 35 control participants. Participants were recruited between 2021 & 2022. Participants with AD were recruited from local retirement homes, with diagnoses confirmed by an experienced neurologist or geriatrician based on core AD biomarkers (e.g., amyloid and tau pathology) and following the National Institute on Aging–Alzheimer's Association guidelines for probable Alzheimer's disease.¹ Control participants were independent, lived at home, and were mostly spouses or companions of AD patients. The control participants were matched with AD patients according to sex, age, and educational level (see Table 1). As expected, the control participants demonstrated greater general cognitive functioning, as assessed with the Mini Mental State Exam (MMSE), than the AD patients.

The sample size was determined based on the number of participants used in previous studies investigating the effects of olfactory stimulation on autobiographical memory in patients with

<table><caption>**Table 1**
Baseline characteristics of Alzheimer's disease (AD) patients and control participants.</caption><thead><tr><th>Characteristic</th><th>AD (n = 33)</th><th>Controls (n = 35)</th><th>Statistical tests</th></tr></thead><tbody><tr><td>Age</td><td>72.48 (5.94)</td><td>72.00 (7.26)</td><td>t(66) = 0.30, p = .76</td></tr><tr><td>Women/men</td><td>19 / 14</td><td>20 / 15</td><td>χ<sup>2</sup>(1, N = 66) = 0.001, p = .97</td></tr><tr><td>Years of formal education</td><td>8.82 (2.52)</td><td>9.83 (3.05)</td><td>t(66) = 1.48, p = .14</td></tr><tr><td>Mini Mental State Exam</td><td>21.94 (1.46)</td><td>28.43 (1.22)</td><td>t(66) = 19.96, p < .001</td></tr></tbody></table>

*Note.* Standard deviations are provided in brackets.

AD.⁸,¹¹,¹²,¹⁴,²⁰,²¹ This approach was adopted to ensure comparability with prior research and to provide sufficient statistical power for exploratory analyses, while remaining feasible given recruitment constraints. Exclusion criteria for all participants included any significant neurological or psychiatric illness, as well as alcohol or drug abuse. Additionally, participants with potential confounding comorbidities, such as COVID-19 or ORL (otolaryngological) diseases, were systematically excluded during the recruitment process. Note that we assessed olfactory acuity based on participants' self-declaration.

### Ethical considerations

The study received approval from the University of Lille Ethics Committee (2017-4-S56) and was conducted in accordance with the principles outlined in the Declaration of Helsinki. All participants, or their legally authorized representatives in the case of patients with AD who were unable to provide full consent, provided informed consent prior to participation. Caregivers were actively involved in the consent process to ensure comprehension and voluntary participation. Participants retained the right to withdraw at any time without any consequences. Data were collected, anonymized, and securely stored according to institutional regulations. Potential side effects of odor exposure were monitored, and none were reported.

### Procedures

Procedures are illustrated in Fig. 1. The present study is a cross-sectional (non randomized intervention) design, in which patients with AD and healthy controls were assessed in two sessions for their

<figure><img src="image_6.png" /><figcaption>**Fig. 1.** Procedures.</figcaption></figure>
autobiographical memory retrieval with and without olfactory stimulation. This design was chosen because it allows for a direct comparison of memory performance between conditions within a well-defined sample, while minimizing the burden on participants, who may have cognitive or attentional limitations. In our procedures, participants were invited to retrieve three specific memories with and without odor exposure, with the order of the conditions counterbalanced across participants. Afterward, participants were invited to retrieve the "who", "where", and "when" details.

### Choice of odor

In the odor-exposure condition, participants were first presented with a set of seven odors (lemon, orange, cinnamon, chocolate, coffee, coconut, peach), displayed in small bottles of scented oil. These odors were selected because they are easily detectable by patients with AD and healthy older adults.²² Each participant was invited to choose their favorite odor. In cases where participants preferred two or more odors, they were asked to select the one they liked most, which was then used for autobiographical cuing. All participants successfully identified a favorable odor. The order of odor and odor-free conditions was counterbalanced, with an approximate delay of five to seven days between the two conditions. Participants were tested individually in their homes or private rooms/apartments (in retirement homes) and were informed that the study examined memory for personal information.

### Autobiographical memory retrieval

After selecting their favorite odor, participants were invited to retrieve three specific memories under both odor and odor-free conditions. Before each recall session, participants were instructed to ensure precision and specificity, focusing on events that lasted no longer than a single day and included spatiotemporal details (e.g., time, location, and individuals present). Each recall session was limited to two minutes, with the timeframe communicated upfront to help participants structure their responses and minimize potential redundancy or distraction. In the odor condition, the experimenter opened a small bottle of the chosen scented oil and placed it under the participant's nose. Participants were instructed to close their eyes and mouth, breathing naturally through their nose. Immediately after odor exposure, participants were prompted to recall the memory. This procedure was repeated for each of the three memories.

### Retrieval details: "Who," "Where," and "When"

The experimenter asked participants to retrieve additional contextual details for each memory:

- "Who": Participants were asked to provide the names of individuals evoked during the event (e.g., "What is the name of that friend?", "What is the name of that teacher?").

- "Where": Participants were asked to name locations mentioned during the event (e.g., "What is the name of that city where you spent that holiday?", "What is the name of that street where you lived?").

- "When": Participants were prompted to provide temporal details such as the year, season, month, and day of the week when the event occurred.

Note that we focused on the retrieval of "who," "where," and "when" details because these represent the core contextual dimensions of episodic memory, allowing an event to be situated in its spatiotemporal framework and linked to the people involved. These dimensions are widely used in both clinical and research settings to operationalize autobiographical specificity, and they can be scored objectively and reliably across participants. Other contextual aspects (e.g., how the event unfolded, subjective feelings) were not included

here because they are more difficult to standardize and score, and because previous work has shown that deficits in "who," "where," and particularly "when" retrieval are hallmark features of autobiographical decline in AD.

### Memory analysis

The answers to the "who", "where" and "when" questions were audio-recorded with the participants' approval. During transcription, we defined the "who" details as the names of any person who was present during the event, with general information not taken into account (e.g., my teacher, my boss). We defined the "where" details as the names of places where the event occurred, with general information not taken into account (e.g., somewhere, in my country, at the seaside). We defined the "when" details as the year, season, month and/or day, with general information not taken into account (e.g., once, in my childhood, on vacation). We attributed one point for each piece of information about: 1) the persons who were present during the event, 2) the place where the event occurred and 3) the time when the event occurred. In other words, we considered, for each participant, a "who" score (the sum of points describing the "who" details), a "where" score (the sum of points describing the "where" details), and a "when" score (the sum of points describing the "when" details). Memory analysis and the experiment, in general, were conducted blind to the study hypothesis. This blinding ensured that the experimenter and individuals scoring the data were not influenced by any expectations regarding the outcomes of the study, thereby minimizing potential biases in data collection and interpretation.

### Statistical analysis

The data are summarized in Table 2, and the raw data are provided in the Appendix. For each variable (i.e., the number of "who", "where", or "when" details), we compared data between groups (i.e., patients with AD vs. control participants) as well as across the two conditions (i.e., odor and odor-free). We used the Mann-Whitney U test for intergroup comparisons and Wilcoxon's signed-rank test for within-group comparisons. We also compared, for each group, the number of "who", "where", or "when" individuals across each condition using Friedman tests followed by Wilcoxon signed-rank tests. We used nonparametric tests because data was skewed. We provided effect sizes using Cohen's *d* criterion²³ (0.20 = small, 0.50 = medium, 0.80 = large). The effect size was calculated for nonparametric tests according to the recommendations of Rosenthal and DiMatteo²⁴ and Ellis.²⁵ For all tests, the level of significance was set as $p \le 0.05$.

<caption>**Table 2**</caption>

The number of "who", "where", and "when" details in the odor and odor-free conditions in Alzheimer's disease (AD) patients and control participants.

<table><thead><tr><th></th><th></th><th>Odor</th><th>Odor-free</th></tr></thead><tbody><tr><td rowspan="3">AD</td><td>Who</td><td>7.82 (1.64)</td><td>6.91 (1.86)</td></tr><tr><td>Where</td><td>6.73 (2.45)</td><td>5.36 (1.69)</td></tr><tr><td>When</td><td>3.85 (2.28)</td><td>2.97 (1.99)</td></tr><tr><td rowspan="3">Controls</td><td>Who</td><td>11.17 (2.76)</td><td>9.74 (2.60)</td></tr><tr><td>Where</td><td>8.14 (2.79)</td><td>6.86 (2.86)</td></tr><tr><td>When</td><td>6.97 (1.88)</td><td>4.94 (2.23)</td></tr></tbody></table>

*Note.* Standard deviations are provided in brackets. Between-group comparisons were performed using Mann-Whitney U tests; within-group comparisons (odor vs. odor-free) were performed using Wilcoxon signed-rank tests. Differences across "who," "where," and "when" were analyzed using Friedman tests followed by Wilcoxon signed-rank post-hoc tests.
## Results

### Between-group comparisons

Regarding between-group comparisons, and in the odor condition, our analysis demonstrated fewer “who” details ($Z = -4.92, p < .001$, Cohen's $d = 1.49$), “where” details ($Z = -2.09, p = .036$, Cohen's $d = 0.52$), and “when” details ($Z = -5.05, p < .001$, Cohen's $d = 1.52$) in patients with AD than in control participants. In the odor-free condition, our analysis also demonstrated fewer “who” details ($Z = -4.32, p < .001$, Cohen's $d = 1.23$), “where” details ($Z = -2.19, p = .028$, Cohen's $d = 0.55$), and “when” details ($Z = -3.35, p = .001$, Cohen's $d = 0.95$) in patients with AD than in control participants. Regarding within-group comparisons, and in the AD group, our analysis demonstrated more “who” details ($Z = -2.09, p = .037$, Cohen's $d = 0.78$), “where” details ($Z = -2.85, p = .004$, Cohen's $d = 0.24$), and “when” details ($Z = -2.02, p = .043$, Cohen's $d = 0.74$) in the odor condition than in the odor-free condition. In the control group, our analysis also demonstrated more “who” details ($Z = -2.60, p = .009$, Cohen's $d = 0.98$), “where” details ($Z = -2.03, p = .042$, Cohen's $d = 0.72$), and “when” details ($Z = -3.59, p < .001$, Cohen's $d = 1.53$) in the odor condition than in the odor-free condition.

### “Who” vs “when” vs “where”

Regarding differences between the “who”, “when”, or “where” details in each condition, our analysis demonstrated significant differences between these details in patients with AD in the odor condition [$X^2(1, N = 33) = 35.52, p < .001$]. Follow-up analysis demonstrated more “who” than “where” details ($Z = -2.08, p = .038$, Cohen's $d = 0.78$), more “who” than “when” details ($Z = -4.81, p < .001$, Cohen's $d = 3.04$), and more “where” than “when” details ($Z = -3.92, p < .001$, Cohen's $d = 1.85$). Analysis also demonstrated significant differences between the “who”, “where”, or “when” details in patients with AD in the odor-free condition [$X^2(1, N = 33) = 39.32, p < .001$]. Follow-up analysis demonstrated more “who” than “where” details ($Z = -3.30, p < .001$, Cohen's $d = 1.40$), more “who” than “when” details ($Z = -4.72, p < .001$, Cohen's $d = 2.85$), and more “where” than “when” details ($Z = -3.83, p < .001$, Cohen's $d = 1.76$). In the control group, analysis demonstrated significant differences between the “who”, “where”, or “when” details in the odor condition [$X^2(1, N = 35) = 37.22, p < .001$]. Follow-up analysis demonstrated more “who” than “where” details ($Z = -3.88, p < .001$, Cohen's $d = 1.68$), more “who” than “when” details ($Z = -4.81, p < .001$, Cohen's $d = 2.78$), and more “where” than “when” details ($Z = -1.97, p = .048$, Cohen's $d = 0.72$). Analysis also demonstrated significant differences between the “who”, “where”, or “when” details in the odor-free condition in the control group [$X^2(1, N = 35) = 42.32, p < .001$]. Follow-up analysis demonstrated more “who” than “where” details ($Z = -3.50, p < .001$, Cohen's $d = 1.47$), more “who” than “when” details ($Z = -5.10, p < .001$, Cohen's $d = 3.40$), and more “where” than “when” details ($Z = -2.83, p = .005$, Cohen's $d = 1.68$).

## Discussion

Because autobiographical decline in patients with AD is mainly characterized by difficulties in retrieving contextual information,¹⁰,²⁶ we investigated whether olfactory stimulation could help patients with AD overcome these difficulties. To this aim, we invited patients with AD to retrieve autobiographical memories with and without odor exposure and invited them to remember who was present, where the event occurred, and when it took place. Our main results indicate that olfactory stimulation significantly increased the number of “who,” “where,” and “when” details recalled in both patients with AD and control participants, suggesting that odor cues may enhance contextual retrieval during autobiographical recall.

### Decline of contextual retrieval in AD

The decline in autobiographical specificity in patients with AD is well established.²⁷,²⁸ This decline is primarily reflected in difficulties retrieving “who,” “where,” and “when” details, leading to a diminished ability to mentally relive past events and a shift toward a general sense of familiarity.²⁹ Laboratory studies on source memory also support this pattern, showing that AD patients struggle to remember contextual information such as who manipulated objects, in which location, or under which conditions.³⁰,³¹ Our findings align with this literature and demonstrate that olfactory stimulation can partially counteract this decline, particularly in mild-stage AD.

### Effects of olfactory stimulation on autobiographical memory in AD

By demonstrating that odor cues specifically enhance the retrieval of “who,” “where,” and “when” details, our study extends prior research on olfactory stimulation in AD.¹¹,¹²,¹⁴⁻¹⁶ Previous studies primarily focused on general vs. specific memories, without examining contextual components. Our work highlights the originality of investigating these core dimensions and provides evidence for a mechanism by which olfactory cues improve autobiographical specificity. This supports the growing evidence for non-pharmacological interventions in AD,³²,³³ which can enhance memory with minimal side effects. Future studies should compare olfactory cues with other sensory modalities, such as music or visual stimuli, to explore differential effects on “who,” “where,” and “when” recall.

### Mechanisms of olfactory-enhanced memory

Odor exposure may reinstate contextual associations during memory retrieval, facilitating recall of “who,” “where,” and “when” details. This associative mechanism likely involves the hippocampus, which integrates information from the perirhinal cortex (“who”) and parahippocampal cortex (“where”), supporting retrieval of spatio-temporal context.³⁴⁻³⁸ Our findings illuminate how olfactory stimulation can help AD patients overcome the challenge of temporal retrieval deficits, a critical component of autobiographical decline. This represents a novel contribution, emphasizing the potential for odor cues to selectively enhance contextual memory components.

### Normal aging

Regarding control participants, our findings are of interest because normal aging has been associated with a decline in autobiographical specificity. For instance, Peters, Fan and Sheldon³⁹ reported that older adults produce fewer specific autobiographies than younger adults. The study of Peters, Fan and Sheldon³⁹ mirrors the literature demonstrating that autobiographical recall is more schematic in older adults than in younger adults.⁴⁰⁻⁴⁵ According to Spencer and Raz,⁴⁶ within episodic memory, the ability to retrieve contextual information is highly vulnerable to the effects of aging. However, despite age-related declines in both episodic memory and olfactory function, research indicates that the ability of odors to evoke autobiographical memories remains robust, albeit with certain nuances, in older adults.⁴⁷,⁴⁸ For instance, Willander and Larsson⁴⁷,⁴⁸ demonstrated that older adults report more emotionally vivid and temporally distant memories in response to odors compared to visual or verbal cues, suggesting that the olfactory system retains its potency as a mnemonic trigger even in later life. Consistent with these findings, our study shows that the application of scent also yielded positive effects on the retrieval of “who,” “where,” and “when” details in healthy older adults, demonstrating that olfactory stimulation can enhance contextual memory even in the absence of AD. These
findings resonate with our study, which demonstrates that olfactory stimulation can mitigate age-related memory decline.

## Limitations

Several limitations of this study should be acknowledged. First, although we excluded participants with known olfactory impairments, we did not conduct an objective assessment of olfactory acuity. Given that olfactory deficits are common in AD, this may have influenced the effectiveness of odor stimulation. Second, the sample size was relatively modest, which may limit the generalizability of the findings. Third, we did not conduct a long-term follow-up; therefore, it remains unknown whether the beneficial effects of olfactory stimulation on autobiographical memory are sustained over time or diminish after the stimulation ends. Finally, our study focused on mild AD, and the extent to which these findings apply to moderate or severe stages of the disease remains to be explored. Addressing these limitations in future research will be essential for clarifying the scope and durability of olfactory-based interventions in AD

## Clinical implications

The positive effects of olfactory stimulation on autobiographical memory in AD suggest potential clinical applications, particularly in improving memory retrieval and emotional engagement. Olfactory interventions can be incorporated into therapeutic settings and daily care routines to support cognitive rehabilitation and reminiscence therapy. Nurses, who are closely involved in patients' everyday lives, are well placed to use familiar scents to stimulate recall and foster meaningful interactions, thereby strengthening patient engagement and emotional connection. Because olfactory stimulation is low-cost, simple, and non-invasive, it can be feasibly integrated into nursing practice as well as clinical protocols. Nonetheless, olfactory sensitivity may decline with age or disease progression, and careful selection of odors is necessary to respect individual preferences and avoid discomfort. Further research should determine the long-term efficacy of this approach and explore how best to integrate it into practical, accessible care frameworks.

## Conclusion

This study highlights the potential of olfactory stimulation to enhance autobiographical memory retrieval in individuals with AD. The findings point to promising clinical applications, particularly for cognitive rehabilitation and nursing care, given the non-invasive and low-cost nature of olfactory interventions. However, several limitations should be acknowledged. The cross-sectional design and absence of long-term follow-up restrict conclusions about the sustained benefits of olfactory stimulation. Moreover, variations in olfactory sensitivity across individuals and disease stages may limit generalizability. Future research should therefore include longitudinal studies to assess long-term efficacy, investigate optimal methods of scent delivery, and determine which types of odors are most effective. Expanding this line of research could provide nurses and clinicians with practical, evidence-based tools to enrich patient care, support reminiscence therapy, and improve quality of life in AD.

## Declaration of competing interest

The authors declare no conflict of interest.

## CRediT authorship contribution statement

**Karim Gallouj:** Writing – review & editing, Supervision, Resources, Methodology. **Pascal Antoine:** Validation, Resources,

**Methodology.** **Guillaume Chapelet:** Writing – review & editing, Validation, Supervision, Investigation. **Mohamad El Haj:** Writing – original draft, Methodology, Investigation, Conceptualization.

## Supplementary materials

Supplementary material associated with this article can be found in the online version at doi:10.1016/j.gerinurse.2026.103857.

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