# Personality traits of aged dogs according to their cognitive status

Audrey Besegher, Sarah Jeannin, Nancy Rebout, Samanta Świerk, Yohan Stephan, Caroline Gilbert, Morgane Robles, Thierry Bedossa, Sara Hoummady

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## To cite this version:

Audrey Besegher, Sarah Jeannin, Nancy Rebout, Samanta Świerk, Yohan Stephan, et al.. Personality traits of aged dogs according to their cognitive status. Applied Animal Behaviour Science, 2025, 292, 10.1016/j.applanim.2025.106844. hal-05327470

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Submitted on 23 Oct 2025

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# Personality traits of aged dogs according to their cognitive status

Audrey Besegher<sup>a,b,*</sup>, Sarah Jeannin<sup>a</sup>, Nancy Rebout<sup>c</sup>, Tiphaine Blanchard<sup>d</sup>, Samanta Świerk<sup>e</sup>, Yohan Stephan<sup>c</sup>, Caroline Gilbert<sup>f,g</sup>, Morgane Robles<sup>c</sup>, Thierry Bedossa<sup>b</sup>, Sara Hoummady<sup>c</sup>

## ARTICLE INFO

**Keywords:**

Aging

Cognitive dysfunction Syndrome

Dog

Environnement

Personality

## ABSTRACT

Canine cognitive dysfunction (CCD) syndrome is a neurodegenerative condition that shares similarities with Alzheimer's disease (AD) in humans. In human studies, high neuroticism, low openness, and low extraversion have been significantly associated with AD diagnosis. Similarly, changes in dog behaviour, including alterations in personality, have been reported as common features in dogs with CCD, but no precise assessment of their changes has yet been realised. The aim of this study (based on the CaniAge cohort) was to compare characteristics of dogs with cognitive impairment (CI dogs) and non-CI dogs in a French senior dog population including owner-reported personality traits between dogs. Data were collected via an online survey, including the CADES scale (Canine Dementia Scale), the Monash Canine Personality Questionnaire, the Canine Owner-Reported Quality of Life (CORQ) assessment, and an environment questionnaire. Dogs aged of 6 years and older were included. Responses were obtained for 566 senior dogs of various breeds, with a median age of 9.86 years (Interquartile range: 8.08–11.98). Among them, 234 were classified as cognitively impaired, including 182 with mild impairment, 44 with moderate impairment, and 8 with severe impairment or dementia. Compared to non-CI dogs, CI dogs scored significantly lower on extraversion and amicability, and higher on neuroticism. After adjustment, CI dogs showed significantly lower amicability and higher neuroticism compared to non-CI dogs. This study is complementary of previous studies regarding CI-characteristics but is also the first to explore personality trait differences between CI and non-CI dogs, supporting observations previously reported in Alzheimer's disease research.

## 1. Introduction

The demographic shift toward an aging dog population (Inoue et al., 2018) has led to an increased interest of pathological aging syndromes such as Canine Cognitive Dysfunction (CCD) or ‘canine dementia’ (Salvin et al., 2010). This neurobehavioral syndrome, affecting progressively aged dogs, presents similarities with Alzheimer’s disease and has been proposed as a spontaneous animal model for early Alzheimer’s disease (Schütt et al., 2016). The prevalence of CCD among dogs older

than 8 years has been estimated in different studies from 14 % up to 60 % (Fast et al., 2013), supporting the relevance of aged dogs in comparative studies of aging and dementia (Benzal and Rodríguez, 2016; Katina et al., 2016; Osella et al., 2007).

This syndrome is characterized by a combination of cognitive symptoms, such as learning deficits, memory impairment, disorientation, and altered social interactions, and non-cognitive neuropsychiatric symptoms, such as disturbances in the sleep-wake cycle, changes in activity levels, and house soiling (Landsberg et al., 2012). Regarding the

Abbreviations: CI, Cognitive Impairment; CCD, Canine Cognitive Dysfunction; AD, Alzheimer's disease; CADES, Canine Dementia Scale; CORQ, Canine Owner-Reported Quality of Life.

* Corresponding author at: LECD Université Paris Nanterre, 200 avenue de la République, Nanterre 92000, France.

E-mail address: audrey.besegher@parisnanterre.fr (A. Besegher).

<footnote><sup>a</sup> LECD Université Paris Nanterre, 200 avenue de la République, Nanterre 92000, France</footnote>

<footnote><sup>b</sup> Agir pour la Vie Animale- Association Agir pour la Vie Animale, 40 Le Quesnoy, Cuy-Saint-Fiacre 76220, France</footnote>

<footnote><sup>c</sup> UniLaSalle, Université d'Artois, IDEALISS, ULR 7519, Mont-Saint-Aignan 76130, France</footnote>

<footnote><sup>d</sup> GenPhySE, Université de Toulouse, INRAE, ENVT, Castanet Tolosan 31326, France</footnote>

<footnote><sup>e</sup> Department of Animal Nutrition and Fisheries, University of Agriculture in Krakow, al. Mickiewicza 24/28, Krakow 30-059, Poland</footnote>

<footnote><sup>f</sup> Ecole Nationale Vétérinaire d'Alfort, 7 avenue du Général de Gaulle, Maisons-Alfort, France</footnote>

<footnote><sup>g</sup> Laboratoire MECADEV, UMR 7179, CNRS/MNHN, 1 Avenue du petit château, Brunoy 91800, France</footnote>
human Alzheimer's disease, the mild stage is characterized by changes in personality (characteristics of individuals that describe and account for consistent patterns of feeling, thinking, and behaving (Jones and Gosling, 2005)) with an increase in neuroticism, a decrease in extraversion and reduced openness, agreeableness and conscientiousness (Wahlin and Byrne, 2011).

Nowadays, some personality traits, such as neuroticism, have been identified as potential risk factors for Alzheimer's disease at the population level (Terracciano and Sutin, 2019). Importantly, long-term prospective studies indicate that such changes do not occur during the preclinical phase (Terracciano et al., 2017), but rather emerge with the onset and progression of dementia. While some authors have reported a specific personality profile linked to Alzheimer's disease (Chatterjee et al., 1992), others have suggested that personality changes may occur more randomly (D'Iorio et al., 2018), highlighting a lack of consensus.

In dogs, the question of whether a specific personality profile is associated with cognitive dysfunction syndrome has not yet been raised. However, some studies have reported behavioural changes in affected dogs, such as increased aggression, anxiety, or other alterations in behaviour (Prpar Mihevc and Majdić, 2019). Moreover, a study on pet dogs aged over 6 years observed some behavioural changes with age (decline in trainability, problem solving, sociability, boldness; Chapagain et al., 2020). Recent publications mentioned a decrease with age of the traits activity/excitability and responsiveness to training in dogs (Wallis et al., 2020). Age-related disease could therefore influence personality. The decrease in boldness in dogs older than 13 years may be explained by aged disease condition like arthritis (physical pain and discomfort may lead them to take fewer risks) (Starling et al., 2013). However, expression of personality traits between individuals with CCD and those without has yet not been well investigated. As geriatric cognitive impairment seems to impact quality of life of affected aged dogs (Benzal and Rodríguez, 2016), more descriptive knowledge may help practitioners to improve the end of life of these individuals. Furthermore, given that canine cognitive dysfunction is associated with decreased activity levels (Bray et al., 2022), it is plausible that affected dogs live in qualitatively different environments, potentially characterized by reduced environmental enrichment or stimulation, which may also contribute to alterations in personality traits. This paper reports the result of a study comparing the characteristics including the personality profile of cognitively impaired (CI) dogs compared with non-CI dogs. Regarding previous data about Alzheimer's, we assume that aged dog with cognitive dysfunction syndrome may have a higher level of neuroticism, a lower score of extraversion, amicability and training focus when compared to aged dogs without cognitive impairment.

## 2. Materials and methods

### 2.1. Methodology

An online survey was developed to recruit a community of French owners with a dog aged 6 years or older, as mild visuospatial deficits seems to be detected as soon from that age in Beagles (Studzinski et al., 2006). This cohort, named CaniAge, will be followed for 2 years. This questionnaire was diffused online through owner and veterinarian community from February 2025 to April 2025. The survey included several sections aimed at capturing different aspects of the dogs' lives and characteristics. First, it incorporated a validated dog personality questionnaire: the Monash Canine Personality Questionnaire (MCPQ; (Ley et al., 2009)). This 26-item scale measures five dimensions of canine personality—Extraversion, Motivation, Training Focus, Amicability, and Neuroticism. These dimensions are broadly comparable to the human OCEAN personality model (Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism), commonly assessed with tools such as the NEO-PI-R (Boyle et al., 2008).

Dog-related factors were selected based on the literature. In addition

to age, which is consistently associated with cognitive dysfunction, sex and neutering status were also included as covariates. Although evidence regarding their role is mixed, with some studies reporting associations (Azkona et al., 2009), and others finding no significant effect (Kim et al., 2023), their inclusion is justified to control for potential confounding effects and to ensure comparability with previous CCD studies.

Additional questionnaires were included to assess specific health and lifestyle aspects. Sleep quality was evaluated using the SNORE questionnaire (Mondino et al., 2023). Frailty (multisystem aging syndrome characterized by decreased physiological and functional reserves and a loss of resilience to stressor (Thillainadesan et al., 2020)) was assessed based on the frailty phenotype scale (Russell et al., 2024). Quality of life was measured using the Canine Owner-Reported Quality of Life questionnaire (CORQ), which also includes items on pain perception (Giuffrida et al., 2018) and sensory decline, assessed through two questions on decreased vision and hearing (Waters et al., 2024). Hearing and vision were collected with three categories: "No," "Yes without impact on quality of life," and "Yes with impact on quality of life." For modeling, sensory decline was dichotomized (Yes = either "Yes" option; No = "No") and entered as an adjustment covariate. Other senses were not evaluated.

The classification of cognitive status was based on a validated owner-based questionnaire, the Canine Dementia Scale (CADES) (Madari et al., 2015). This tool is based on 17 items related to behavioural changes and evaluate four different domains: spatial orientation, social interaction, sleep-wake cycle and house soiling. Dogs are then assigned to different clinical stages based on the total score: normal (0–7), mild (8–23), moderate (24–44) and severe (45–95). The variable has been dichotomized into two categories: normal (0–7) and impaired (8–95). This questionnaire is validated for assessing canine cognitive dysfunction; however, as the study relies on owner-reported data, and given the necessity of a clinical evaluation to exclude medical conditions that may lead to behavioural changes, the term "cognitively impaired dogs" will be used rather than "dogs with cognitive dysfunction."

### 2.2. Statistical analysis

Statistical analyses were performed on R (R version 4.4.1). Medians and interquartile range (IQR) were provided for all quantitative variables and percentage for binary variables.

Data were analysed in two steps, the first based on univariate analysis to identify potential confounding factors which were included in adjusted models. Regrading univariate analysis for comparison between CI dogs and non-CI dogs, after density analysis, non-parametric Mann-Whitney tests were used. For comparisons involving percentages, chi-square tests were used. No correction for multiple comparisons was applied at this stage, since only biologically plausible variables or those with a priori hypotheses were tested, and no conclusions were drawn from univariate results, which served solely as a screening step before multivariable modelling (Rothman, 1990; Hooper, 2025) (Rothman, 1990; Hooper, 2025).

The following section outlines the methodology employed to construct the multivariable models used in the analysis. Regarding multivariate model on cognitive status personality traits, sex, age, reproductive status and size of the dog are essential in a study about cognitive impairment and were automatically included into the multivariable model based on previous studies (Azkona et al., 2009). Among variables hypothesized to be associated with cognitive impairment, variables with a *P* < 0.20 in univariate analyses were included into the multivariable models as possible confounding factors (Mickey and Greenland, 1989). An individual model was developed for each personality trait. Therefore, the choice of the variables included into the multivariable model was not based upon automated variable selection methods. Multicollinearity was checked using variance inflation factor (VIF) values and where always lower than 2 indicating no notable issue
of multicollinearities (Midi et al., 2010).

Based on this methodology, to study the association between dog personality traits and cognitive status, a multivariate logistic regression has been built between each personality traits (as each of them is supposed to be independent) and cognitive status with adjustment on sex, reproductive status, age of the dog, frailty status, hearing impairment, visual impairment, SNORE score and CORQ score. No interaction was included in the multivariable models. A p-value < 0.05 was considered statistically significant.

# 3. Results

## 3.1. Profiles of dogs and owners

A total of 566 owners have been selected to the survey. Descriptive statistics showed that 51 % of the dogs were females and 81 % of all dogs were neutered. In the CaniAge population, dogs were distributed as follows: 2.3 % miniature (<3.6 kg), 17.5 % small (3.6–10 kg), 42.8 % medium (10–25 kg), 35.5 % large (25–45.5 kg), and 1.9 % giant (>45.5 kg). Owners reported that 62 % of the population consisted of purebred dogs, and the median age was 9.84 years (IQR: 8.09–11.98). Regarding the environment, 28 % of dogs were living exclusively in an urban area and 76 % in a house, 21 % of dogs were living with at least one child. Regarding owner characteristics, 92 % were female, 42 % had a professional activity in relation with animals and 21 % were aged of 45 years and older. In terms of cognitive status, 332 dogs were classified as cognitively non-impaired while 234 dogs were classified as cognitively impaired (mild: 182 dogs (32.2 %); moderate: 44 dogs (7.8 %); severe: 8 dogs (1.4 %)).

## 3.2. Characteristics of cognitively impaired dogs

In univariate analyses, CI dogs were significantly older (10.76 years, IQR [8.76–13.55]) compared to non-CI dogs (9.28 years, IQR [7.89–11.04]; p < 0.001; Table 1) and were also more frequently frail (15 % for CI dogs versus 4 % for non-CI dog; p < 0.001; Table 1). Quality of life, as measured by the CORQ score, was lower for CI dogs compared to non-CI dogs (5.1, IQR [4.4–5.9] versus 6.1, IQR [5.1–6.6], p < 0.001, Table 1). CI dogs were significantly more frequently affected by a chronical disease (82 % for CI dogs versus 57 % for non-CI dogs;

<caption>**Table 1**</caption>

General characteristics of cognitively impaired and unimpaired dogs. Quantitative variables are expressed as median and interquartile range (IQR). Categorical binary variables are reported as frequencies and percentages. Non-parametric Mann-Whitney tests were used for quantitative variables and chi-square tests for comparison of percentage.

<table><thead><tr><th>Dogs<br>characteristics</th><th>NoN-CI DOGS<br>(n = 332)</th><th>CI DOGS<br>(n = 234)</th><th>P-value<br>Univariate</th></tr></thead><tbody><tr><td><strong>CARACTERISTICS</strong></td><td></td><td></td><td></td></tr><tr><td>Female</td><td>166 (50 %)</td><td>122 (52 %)</td><td>0.7</td></tr><tr><td>Neutering</td><td>262 (79 %)</td><td>196 (83 %)</td><td>0.18</td></tr><tr><td>Small breed</td><td>59 (18 %)</td><td>53 (22 %)</td><td>0.18</td></tr><tr><td>Age (Years)</td><td>9.28 [7.89–11.04]</td><td>10.76<br>[8.76–13.55]</td><td>&lt; 0.001</td></tr><tr><td>Physical_frailty</td><td>13 (4 %)</td><td>35 (15 %)</td><td>&lt; 0.001</td></tr><tr><td>Chronic<br>disease</td><td>191 (57 %)</td><td>191 (82 %)</td><td>&lt; 0.001</td></tr><tr><td>CORQ score</td><td>6.12 [5.06–6.59]</td><td>5.11<br>[4.35–5.88]</td><td>&lt; 0.001</td></tr><tr><td>SNORE Score</td><td>9 [7–12]</td><td>12 [8–19]</td><td>&lt; 0.001</td></tr><tr><td>Decrease<br>audition</td><td>60 (18 %)</td><td>110 (47 %)</td><td>&lt; 0.001</td></tr><tr><td>Decrease vision</td><td>89 (26.8 %)</td><td>132 (56.4 %)</td><td>&lt; 0.001</td></tr><tr><td>Owner_Female</td><td>312 (94 %)</td><td>211 (91 %)</td><td>0.24</td></tr><tr><td>Children</td><td>65 (20 %)</td><td>56 (24 %)</td><td>0.25</td></tr><tr><td>Owner age ≥ 45</td><td>81 (24.4 %)</td><td>39 (16.7 %)</td><td>0.03</td></tr><tr><td>House</td><td>259 (78 %)</td><td>174 (74 %)</td><td>0.36</td></tr></tbody></table>

p < 0.001; Table 1), had a decrease in audition (47 % for CI dogs versus 18 % for non-CI dogs; p < 0.001; Table 1) and vision (56 % for CI dogs versus 27 % for non-CI dogs; p < 0.001; Table 1) and an lower quality of sleep (Score SNORE: CI 12 [8–19]; non-CI; 9 [7–12]; p < 0.001; Table 1). CI dogs had less frequently owners aged 45 years old and more (17 %) compared to non-CI (24 %; p = 0.03). No significant differences were observed for the available environmental proxies (e.g., housing category); these variables did not contribute meaningfully in adjusted models. Environmental variables were evaluated as potential co-factors, but none showed an independent association and thus were not included in the multivariable model.

## 3.3. Personality of dogs

Cognitively impaired dogs had a significantly lower score for extraversion (50.00; IQR [36.81–66.67]) compared to non CI dogs (55.56; IQR [44.44–72.22]; p < 0.001; Table 2), a significantly lower score for amicability (CI: 80.00; IQR [63.33–90.00]; non-CI: 86.67; IQR [73.33–94.17]; p < 0.001; Table 2) than non-CI dogs (Table 2) and a significantly higher score for neuroticism (CI: 45.83; IQR [33.33–62.50]; non-CI: 41.67; IQR [29.17–58.33]; p < 0.001). After adjustments on age, sex, reproductive status, frailty status, decrease of audition and vision, the SNORE score and presence of chronical disease, the association between amicability, neuroticism and CI-status persisted (OR: 0.99; 95 % CI [0.98–1] p = 0.04 and OR 1.02 95 %CI [1.01–1.03] p < 0.01; respectively; Table 2; Fig. 1).

# 4. Discussion

This study is the first to explore age-related cognitive impairment in a French dog population, and the first to investigate canine personality traits in this context. The multivariate analysis showed differences in the neuroticism and amicability scores of CI dogs compared to non-CI dogs. This observation aligns with human studies comparing the beginning of Alzheimer's disease with healthy subjects and reporting a lower agreeableness score (which is close to the amicability of the canine personality questionnaire) and a higher neuroticism (D'Iorio et al., 2018). High neuroticism is considered as a risk factor to develop Alzheimer's in humans (Johansson et al., 2014; Terracciano et al., 2021). The other personality trait differences reported in human studies (i.e: extraversion, conscientiousness) were not significant in the present analysis after adjustment on age and cofounding factors, which may be related to the structure of the personality tests: personality traits described by human test like NEO-PI-R (NEO Personality Inventory; Costa, McCrae, 2008) may be somehow different from the personality traits described by dog tests like MCPQ.

Extraversion has been related with pain score in dogs (Lush and Iji- chi, 2018), dogs with lower extraversion may show fewer behavioural signs of pain, potentially leading to underestimation by their owners. In the present study, extraversion was no longer associated with reduced cognitive performance once age and pain were accounted for. Although pain was not assessed directly, it was considered through the overall quality of life score derived from the CORQ scale (Giuffrida et al., 2018; Mondino et al., 2024). This indirect measure warrants some caution in interpretation, but the findings may nonetheless suggest that the decrease in extraversion observed in affected dogs relative to unaffected counterparts may be attributable to their older age, and consequently, a higher likelihood of experiencing pain. In contrast, neuroticism remained significantly associated with cognitive impairment after adjustment on age (based on the finding of a recent study highlighting that insecurity in dogs—a trait closely related to human neuroticism—seems to decrease with age (Salonen et al., 2023)). Further investigation is warranted to determine whether this trait constitutes a risk factor for the development of cognitive dysfunction, which will be explored through longitudinal follow-up of the CaniAge cohort.

This study also assessed physical frailty in dogs, using a recently
<caption>**Table 2**</caption>

Personality and lifestyle of cognitively impaired and unimpaired dogs. Quantitative variables are expressed as median and interquartile range (IQR). Categorical binary variables are reported as frequencies and percentages. In univariate analysis, non-parametric Mann-Whitney tests were used for quantitative variables and chi-square tests for comparison of percentages. Logistic multivariate models were used for each personality traits adjusted on age, sex, reproductive status, CORQ score, presence of physical frailty, small breed, decrease vision, decrease audition, SNORE score and presence of chronic disease. A p-value < 0.05 is considered as significant.

<table><thead><tr><th>Dogs<br>characteristics</th><th>NoN-CI DOGS<sup>a</sup><br>(n = 332)</th><th>CI DOGS (n = 234)</th><th>P-value<br>Univariate</th><th>Adjusted model p-value</th></tr></thead><tbody><tr><td colspan="5">PERSONALITY TRAITS</td></tr><tr><td>Extraversion</td><td>55.56<br>[44.44-72.22]</td><td>50.00<br>[36.81-66.67]</td><td>&lt; 0.001</td><td>0.49</td></tr><tr><td>Motivation</td><td>66.67 [53.33-80]</td><td>66.67<br>[53.33-80.00]</td><td>0.9</td><td>0.33</td></tr><tr><td>Trainability<br>Focus</td><td>80 [61.11-88.89]</td><td>75 [61.11-86.11]</td><td>0.08</td><td>0.08</td></tr><tr><td>Amicability</td><td>86.67<br>[73.33-94.17]</td><td>80 [63.33-90]</td><td>&lt; 0.001</td><td>0.04</td></tr><tr><td>Neuroticism</td><td>41.67 [29.17-58.33]</td><td>45.83<br>[33.33-62.50]</td><td>&lt; 0.01</td><td>&lt; 0.01</td></tr></tbody></table>

<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Adjusted Odd Ratio – Personality traits and Cognitive impairment Status. These adjusted Odds Ratio were calculated using 5 models (each with one personality trait and adjusted on canine age, sex of the dog, reproductive status, CORQ, presence of physical frailty, Small and miniature breed, decrease vision, decrease audition, SNORE score and presence of chronic disease).</figcaption></figure>

adapted version of Fried's frailty (Fried et al., 2001) phenotype (adapted by Russell et al., 2024). Physical frailty, independently of age, has been associated with an increased risk of mortality. In the current study, physical frailty appeared to be associated with cognitive decline. However, after adjusting for age and the presence of chronic disease, this association was no longer significant. This finding highlights the potential relevance of a condition described in human medicine but not yet investigated in dogs: cognitive frailty—defined as the coexistence of physical frailty and cognitive impairment, in the absence of dementia (Kelaiditi et al., 2013).

Consistent with our findings and with prior evidence, sensory deficits should be routinely accounted for when modelling dog cognition and behaviour. In particular, owner-reported sensory impairments are associated with behavioural signs linked to cognitive decline (Szabó et al., 2018), supporting the current inclusion of hearing and vision status as covariates in all multivariable analyses. A limitation of the present work is that olfactory function was not assessed, as we judged it difficult for owners to evaluate reliably with a single questionnaire item. There is also other limitations. The present study used an owner-focused personality test with the risk to underestimate the personality dimension with only 26-items. However, the purpose of this study was to focus on easy tools for clinical use like the MCPQ, to apply this test to a senior routine consultation. A second limit is the use of a questionnaire to assess cognitive dysfunction syndrome. As mentioned in previous studies, the syndrome may be concomitant with other aging-related disease which can lead to behaviour changes, which explain the use of

“cognitively impaired” mentioned in this paper. These results have to be confirmed with other studies and a test such as the Modified Vienna Canine Cognitive Battery for CCD Diagnostic (Chapagain et al., 2020). For ethical reasons, asking owners of older dogs—potentially affected by cognitive impairment—to transport their pets to unfamiliar examination rooms is questionable, as such changes in environment may elevate stress levels and influence the results. Therefore, this study was designed as a nationwide cohort followed remotely through structured questionnaires. Our sample was strongly female-skewed (92 % female respondents), a common feature of self-selected owner surveys. This may introduce reporting bias and limit generalizability to households with male primary caregivers. We did not adjust for owner sex because our analysis focused on dog-level factors and the very small number of male respondents precluded a meaningful adjustment. Future studies should broaden recruitment beyond female-dominated channels and consider quota/stratified sampling and post-stratification weighting to improve representativeness. Finally, our cohort exhibited a higher neutering rate than national estimates (FACCO ≈ 66 %), which is consistent with selection bias toward older pets and owners more engaged in preventive care inherent to our recruitment strategy. Because the aim of this study was to examine the association between personality traits and the presence of cognitive dysfunction, we a priori included neutering status and owner-related variables as covariates in the multivariable models to control for potential confounding.

In parallel, rather than maximizing baseline sample size, CaniAge prioritizes longitudinal retention and deep phenotyping; ~600 dogs will
be followed with repeated measures to enhance internal validity and trajectory precision while limiting attrition biases: In future stages of the project, owners will be invited to perform simple behavioural and sensory tests at home, record their dogs, and submit the videos to the research team, following a protocol previously used during the COVID-19 pandemic in a study on immunosenescence in elderly cats (Pirrone et al., 2024). Owners will also be given the opportunity to provide faecal samples, allowing investigation of the relationship between gut microbiota and cognitive performance (Kubinyi et al., 2020).

It is important to note that the study population is not fully representative of the general French dog population, as indicated by the high proportion of owners working in animal health-related professions. However, the aim of this study was not to estimate the prevalence of cognitive dysfunction, but rather to explore associations between personality traits and cognitive decline. Interestingly, having a background in animal health did not appear to be a confounding factor and was not included in the model, as this group did not show a different percentage of cognitively impaired dogs compared to the rest of the sample.

This preliminary study encourages the inclusion of personality assessment in geriatric follow-up and geriatric studies.

## 5. Conclusion

The present study highlights that dogs with cognitive dysfunction exhibit a distinct personality profile compared to cognitively unimpaired dogs, characterised by lower levels of amicability and higher levels of neuroticism. Together, these results provide valuable insights for future investigations into both risk and protective factors associated with the development of cognitive dysfunction. They may also support the development of clinical strategies to improve the quality of life and welfare of aging dogs.

## Ethical considerations

Our study did not include any animal experiments as defined in French law.

Declaration of Generative AI and AI-assisted technologies in the writing process

Generative AI (GPT-4o) was utilized by the authors to support language refinement and provide assistance with R software syntax. All outputs generated by the AI were carefully reviewed and revised by the authors, who assume full responsibility for the integrity and accuracy of the final manuscript.

## Funding

This research did not receive any specific grant from funding agencies in the public, commercial or non-for-profit sectors. The work was supported by shelter AVA through a CIFRE contract via ANRT funding salary for AB, and by UniLaSalle for the salary of MR, YS, NR, SH.

## CRediT authorship contribution statement

**Thierry Bedossa:** Writing – review & editing, Funding acquisition.
**Caroline Gilbert:** Writing – review & editing, Conceptualization.
**Samanta Świerk:** Writing – review & editing.
**Yohan Stephan:** Writing – review & editing, Conceptualization.
**Nancy Rebout:** Supervision, Methodology, Formal analysis.
**Tiphaine Blanchard:** Writing – review & editing.
**Audrey Besegher:** Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis.
**Sarah Jeannin:** Writing – review & editing, Writing – original draft, Visualization, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.
**Sara Hoummady:** Writing – review & editing, Writing – original draft, Visualization, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.
**Morgane Robles:**

Writing – review & editing, Formal analysis, Conceptualization.

## Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgements

We thank all the participating dog owners.

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