Owner reported sensory impairments affect behavioural signs associated with cognitive decline in dogs

Dual sensory impairments in companion dogs: Prevalence and relationship to cognitive impairment

PURPOSE

Many older dogs (Canis lupus familiaris) develop cognitive impairment. Dog owners often describe impairments in multiple sensory functions, yet the relationships between sensory and cognitive function in older dogs is not well understood.

METHODS

We performed assessments of dog vision and hearing, both clinically (n = 91, electroretinography and brainstem auditory evoked potential) and via validated questionnaire (n = 238). We determined prevalence of sole and dual hearing/vision impairments in younger (<8 years) and older (≥8 years) dogs. Impairment cutoffs were determined using data from young dogs. We assessed the relationships between questionnaire-assessed vision and/or hearing impairments and cognitive impairment using logistic regression.

RESULTS

Younger and older dog groups had similar distributions of sex and purebred/mixed breed status. Sex had no relationship to prevalence of sensory impairments. Older dogs had higher prevalence of hearing, vision, and dual sensory impairments, assessed both clinically and by questionnaire (P<0.001), and cognitive impairment assessed by questionnaire (P<0.001). Dogs had higher prevalence of reported cognitive impairment when owners reported dual vision and hearing impairments (79-94%, versus 25-27% in dogs with no sensory impairments), which was most consistent in dogs aged ≥8 years. In these older dogs, dual vision/hearing impairments were associated with a significantly increased risk of cognitive impairment (1.8-2.0 odds ratio).

CONCLUSION

Dogs aged ≥8 years are at higher risk for dual hearing/vision impairments and associated cognitive impairments. The causal relationship between these impairments is not defined, but clinical consideration of these multimorbidity risks should be made in older dogs.

Advancing the early detection of canine cognitive dysfunction syndrome with machine learning-enhanced blood-based biomarkers

Up to half of the senior dogs suffer from canine cognitive dysfunction syndrome (CCDS), the diagnosis method relies on subjective questionnaires such as canine cognitive dysfunction rating (CCDR) scores. Therefore, the necessity of objective diagnosis is emerging. Here, we developed blood-based biomarkers for CCDS early detection. Blood samples from dogs with CCDR scores above 25 were analyzed, and the biomarkers retinol-binding protein 4 (RBP4), C-X-C-motif chemokine ligand 10 (CXCL10), and NADPH oxidase 4 (NOX4) were validated against neurodegenerative models. Lower biomarker levels were correlated with higher CCDR scores, indicating cognitive decline. Machine-learning analysis revealed the highest predictive accuracy when analyzing the combination of RBP4 and NOX4 using the support vector machine algorithm and confirmed potential diagnostic biomarkers. These results suggest that blood-based biomarkers can notably improve CCDS early detection and treatment, with implications for neurodegenerative disease management in both animals and humans.

Success in the Natural Detection Task is influenced by only a few factors generally believed to affect dogs' olfactory performance

Research into dogs' olfactory ability is growing rapidly. However, generalising based on scientific results is challenging, because research has been typically conducted on a few specially trained subjects of a few breeds tested in different environmental conditions. We investigated the effects of temperature and humidity (outdoors), age, test location, sex, neutering status, and repeated testing (outdoors and indoors) on the olfactory performance of untrained family dogs (N = 411) of various breeds. We employed the Natural Detection Task with three difficulty levels, from which we derived two performance metrics: Top Level and Success Score. Temperature (0-25 °C) and humidity (18-90%) did not affect olfactory performance. Young adult dogs surpassed other age groups in reaching the Top Level. Sex and neutering status showed no discernible influence on Top Level and Success Score. Dogs performed better in both metrics when tested indoors compared to outdoors. In the test-retest procedure no significant learning effect was observed. We confirmed on untrained companion dogs that olfactory performance declines with age and rejected some factors that have been previously hypothesised to significantly affect dogs' olfactory success. The influence of the testing environment was notable, emphasising the need to consider various factors in understanding dogs' olfactory capabilities.

Differential behavioral aging trajectories according to body size, expected lifespan, and head shape in dogs

The twofold life expectancy difference between dog breeds predicts differential behavioral and cognitive aging patterns between short- and long-lived dogs. To investigate this prediction, we conducted a cross-sectional analysis using survey data from over 15,000 dogs. We examined the effect of expected lifespan and three related factors (body size, head shape, and purebred status) on the age trajectory of various behavioral characteristics and the prevalence of canine cognitive dysfunction (CCD). Our findings reveal that, although age-related decline in most behavioral characteristics began around 10.5 years of age, the proportion of dogs considered "old" by their owners began to increase uniformly around 6 years of age. From the investigated factors, only body size had a systematic, although not gradual, impact on the aging trajectories of all behavioral characteristics. Dogs weighing over 30 kg exhibited an earlier onset of decline by 2-3 years and a slower rate of decline compared to smaller dogs, probably as a byproduct of their faster age-related physical decline. Larger sized dogs also showed a lower prevalence of CCD risk in their oldest age group, whereas smaller-sized dogs, dolichocephalic breeds, and purebreds had a higher CCD risk prevalence. The identification of differential behavioral and cognitive aging trajectories across dog groups, and the observed associations between body size and the onset, rate, and degree of cognitive decline in dogs have significant translational implications for human aging research, providing valuable insights into the interplay between morphology, physiological ageing, and cognitive decline, and unravelling the trade-off between longevity and relative healthspan.

Age-related effects on a hierarchical structure of canine cognition

The current study investigates whether there are statistically independent age-related influences on the canine cognitive structure and how individual factors moderate cognitive aging on both cross-sectional and longitudinal samples. A battery of seven tasks was administered to 129 pet dogs, on which exploratory and confirmatory factor analyses were employed to unveil the correlational structure underlying individual differences in cognitive performance. The best-fitting model featured a hierarchical structure with two first-order cognitive domains (individual problem solving, learning) and a second-order common factor. These higher order factors exhibited consistency over a period of at least 2.5 years. External validation linked the common factor positively to discrimination and reversal learning performance, exploration, neophilia, activity/excitability, and training level while negatively to cognitive dysfunction symptoms, suggesting that it is a good candidate for a general cognitive factor (canine g). Structural equation models identified three distinct age-related influences, operating on associative learning, on memory, and on canine g. Health status moderated the negative age-canine g relationship, with a stronger association observed in dogs with poorer health status, and no relationship for dogs in good health. On a longitudinal sample (N = 99), we showed that the direction and magnitude of change in canine g over up to 3 years is affected by various interactions between the dogs' age, communication score, baseline performance, and time elapsed since the baseline measurement. These findings underscore the presence of a general cognitive factor in dogs and reveal intriguing parallels between human and canine aging, affirming the translational value of dogs in cognition and aging research.

The Relationship between Signs of Medical Conditions and Cognitive Decline in Senior Dogs

Canine cognitive dysfunction syndrome (CCDS) is a progressive age-related neurodegenerative disorder in dogs. Minimal research has been performed to investigate how clinical signs may be impacted by other medical conditions. A cross-sectional study was performed using the Canine Cognitive Assessment Scale (CCAS) to evaluate cognitive impairment as reported by owners. Owner-reported health-related measures included behaviour changes, the body condition score, and veterinary diagnoses of disease. The responses from 804 dogs in the last 25% of their expected lifespan were analysed. Factors were identified in the owner-reported behavioural signs of disease representing pathologies in four body systems: musculoskeletal-neurological, digestive, metabolic, and dermatological, with the items comprising these factors also compiled into a cumulative measure of health. The results showed a strong correlation between the CCAS score and both the musculoskeletal-neurological factor and the overall cumulative measure of health. Moderate correlations between the CCAS score and the digestive factor and metabolic factor were also observed. The correlation between the dermatological factor and the CCAS score was weak. This study highlights the need to screen dogs for concurrent diseases when using scales to assess cognitive impairment and to monitor dogs who have health conditions, particularly those that are painful, for the onset of cognitive impairment.

Associations between physical activity and cognitive dysfunction in older companion dogs: results from the Dog Aging Project

Canine cognitive dysfunction (CCD) is a form of dementia that shares many similarities with Alzheimer's disease. Given that physical activity is believed to reduce risk of Alzheimer's disease in humans, we explored the association between physical activity and cognitive health in a cohort of companion dogs, aged 6-18 years. We hypothesized that higher levels of physical activity would be associated with lower (i.e., better) scores on a cognitive dysfunction rating instrument and lower prevalence of dementia, and that this association would be robust when controlling for age, comorbidities, and other potential confounders. Our sample included 11,574 companion dogs enrolled through the Dog Aging Project, of whom 287 had scores over the clinical threshold for CCD. In this observational, cross-sectional study, we used owner-reported questionnaire data to quantify dog cognitive health (via a validated scale), physical activity levels, health conditions, training history, and dietary supplements. We fit regression models with measures of cognitive health as the outcome, and physical activity-with several important covariates-as predictors. We found a significant negative relationship between physical activity and current severity of cognitive dysfunction symptoms (estimate =  - 0.10, 95% CI: - 0.11 to - 0.08, p < 0.001), extent of symptom worsening over a 6-month interval (estimate =  - 0.07, 95% CI: - 0.09 to - 0.05, p < 0.001), and whether a dog reached a clinical level of CCD (odds ratio = 0.53, 95% CI: 0.45 to 0.63, p < 0.001). Physical activity was robustly associated with better cognitive outcomes in dogs. Our findings illustrate the value of companion dogs as a model for investigating relationships between physical activity and cognitive aging, including aspects of dementia that may have translational potential for Alzheimer's disease. While the current study represents an important first step in identifying a relationship between physical activity and cognitive function, it cannot determine causality. Future studies are needed to rule out reverse causation by following the same dogs prospectively over time, and to evaluate causality by administering physical activity interventions.

A novel task of canine olfaction for use in adult and senior pet dogs

While much work has been done in the field of canine olfaction, there has been little exploration of hyposmia or anosmia. This is partly due to difficulties in reducing confounds like training history and environmental distraction. The current study describes a novel olfaction test using spontaneous search behavior in dogs to find a hidden food treat in a three-choice task with both light-phase and dark-phase conditions. The study was performed in 18 adult control dogs, 18 senior/geriatric dogs enrolled in a longitudinal aging study, and a single dog with severe nasal pathology. In the senior/geriatric and control groups, dogs performed with higher accuracy (p < 0.0001) and were less likely to show biased selection strategy (p < 0.01) in the dark-phase than light-phase. While senior/geriatric dogs performed above chance, they had lower accuracy in the dark-phase compared to controls (p = 0.036). Dogs who scored higher on an owner questionnaire of cognitive decline showed a positive correlation with performance in the dark-phase; performance on additional cognitive tests did not correlate with performance in the dark-phase. This task can be used to quantify canine olfaction using clearly defined endpoints and spontaneous behaviors thus making it feasible to compare between and within groups of pet dogs.

Relationship between engagement with the impossible task, cognitive testing, and cognitive questionnaires in a population of aging dogs

Introduction

The aim of this study was to evaluate the engagement of aging dogs with a cognitively challenging and potentially frustrating task (the impossible task). Based on previous observations, we predicted that dogs showing signs of cognitive impairment in other cognitive tests and owner-completed questionnaires would show reduced engagement with the task.

Methods

In this task, dogs were shown a piece of food in a clear container that they could not open; time spent interacting with the container and the experimenter was measured. While the impossible task has not been used as a measure of frustration, the parameters of the test design creates a potential frustrate state, making this assessment appropriate. Thirty-two dogs enrolled in a longitudinal aging study participated in the study. Owners were asked to complete two cognitive dysfunction screening questionnaires (Canine Dementia Scale [CADES] and Canine Cognitive Dysfunction Rating Scale [CCDR]) as well a questionnaire assessing general frustration. Dogs participated in multiple measures of cognitive function as well the impossible task.

Results

Latency to disengage from the impossible task was faster for dogs with higher total (more impaired) CADES (p = 0.02) and total CCDR (p = 0.04) scores. Latency to disengage also correlated with decreased performance in cognitive tests observing social cues (p = 0.01), working memory (p ≤ 0.001), spatial reasoning and reversal learning (p = 0.02), and sustained attention (p = 0.02).

Discussion

The high correlation with several cognitive measures and the ease of administration of this test makes it a useful tool in evaluating canine cognitive dysfunction syndrome, however it is unclear if increased frustration or other cognitive processes are contributing to the observed changes.

Biologia Futura: four questions about ageing and the future of relevant animal models

Understanding how active and healthy ageing can be achieved is one of the most relevant global problems. In this review, I use the "Four questions" framework of Tinbergen to investigate how ageing works, how it might contribute to the survival of species, how it develops during the lifetime of (human) individuals and how it evolved. The focus of ageing research is usually on losses, although trajectories in later life show heterogeneity and many individuals experience healthy ageing. In humans, mild changes in cognition might be a typical part of ageing, but deficits are a sign of pathology. The ageing of the world's populations, and relatedly, the growing number of pathologically ageing people, is one of the major global problems. Animal models can help to understand the intrinsic and extrinsic factors contributing to ageing.

Two valid and reliable tests for monitoring age-related memory performance and neophobia differences in dogs

The prolonged lifespan of companion dogs has resulted in increased behavioural and physical challenges linked to old age. The development of behavioural tests to identify and monitor age-related differences has begun. However, standardised testing requires validation. The present study aimed to assess external validity, interobserver reliability, and test-retest reliability of an indoor test battery for the rapid assessment of age-related behavioural differences in dogs. Two experimenters tested young dogs (N = 20, mean age ± SD = 2.7 ± 0.4 years) and old dogs (N = 18, mean age ± SD = 11.8 ± 1.3 years) in the test battery once and then again after two weeks. Our results found external validity for two subtests out of six. On both test occasions, old dogs committed more errors than young dogs in a memory subtest and showed more object avoidance when encountering a novel object. Interobserver reliability and test-retest reliability was high. We conclude that the Memory and Novel object subtests are valid and reliable for monitoring age-related memory performance and object neophobic differences in dogs.

Relationship between hearing, cognitive function, and quality of life in aging companion dogs

Background

Elderly people with presbycusis are at higher risk for dementia and depression than the general population. There is no information regarding consequences of presbycusis in dogs.

Objective

Evaluate the relationship between cognitive function, quality of life, and hearing loss in aging companion dogs.

Animals

Thirty‐nine elderly companion dogs.

Methods

Prospective study. Hearing was evaluated using brainstem auditory evoked response (BAER) testing. Dogs were grouped by hearing ability. Owners completed the canine dementia scale (CADES) and canine owner‐reported quality of life (CORQ) questionnaire. Cognitive testing was performed, and cognitive testing outcomes, CADES and CORQ scores and age were compared between hearing groups.

Results

Nineteen dogs could hear at 50 dB, 12 at 70 dB, and 8 at 90 dB with mean ages (months) of 141 ± 14, 160 ± 16, and 172 ± 15 for each group respectively (P = .0002). Vitality and companionship CORQ scores were significantly lower as hearing deteriorated (6.6‐5.4, 50‐90 dB group, P = .03 and 6.9‐6.2, 50‐90 dB group, P = .02, respectively). Cognitive classification by CADES was abnormal in all 90 dB group dogs and normal in 3/12 70 dB group and 11/19 50 dB group dogs (P = .0004). Performance on inhibitory control, detour and sustained gaze tasks decreased significantly with hearing loss (P = .001, P = .008, P = .002, respectively). In multivariate analysis, higher CADES score was associated with worse hearing (P = .01).

Conclusions and Clinical Importance

Presbycusis negatively alters owner‐pet interactions and is associated with poor executive performance and owner‐assessed dementia severity.

Physiotherapy Improves Dogs’ Quality of Life Measured with the Milan Pet Quality of Life Scale: Is Pain Involved?

Simple Summary

Recent scientific evidence highlights the importance of assessing quality of life in veterinary patients. Quality of life reflects the well-being of animals from the physical, psychological, and social point of view, as well as the safety and freedom within their environment. In the current study, the quality of life of 20 adult dogs was measured at the beginning and at the end of a physiotherapy treatment, and the relationship with their clinical symptoms was investigated. The dogs underwent various physiotherapy procedures due to neurological, orthopedic, and degenerative conditions and had various degrees of lameness and pain. The assessment of the severity of the condition, diagnosed by the clinician, and the observations on the physical quality of life provided by the dog owners were aligned. In addition, the analysis indicated that the psychological quality of life of the dogs improved following the physiotherapy treatment, highlighting the emotional impact of the medical conditions on the dogs. Furthermore, the social quality of life was negatively impacted by the severity of the lameness, emphasizing how the medical conditions affected all aspects of the dog’s life. These results reveal the importance of considering psychological and emotional aspects when assessing the health of veterinary patients.

Abstract

Quality of life is defined as an individual’s satisfaction with its physical and psychological health, its physical and social environment, and its ability to interact with the environment. Understanding companion dogs’ QOL can help veterinarians and owners know when treatment options have successfully alleviated symptoms of disease in such fields as veterinary physiotherapy. For this study, 20 adult dogs were selected from patients of a physiotherapy referral center with orthopedic, neurological, and/or degenerative conditions. The severity of the medical problem was ranked, and the symptoms, the treatment plan, and demographic data were recorded at the time of the physical examination. In addition, the owner of the dog was asked to fill out a questionnaire on the quality of life of the pet (the Milan Pet Quality of Life scale) at the time of the first consultation as well as the last follow-up after the treatment. The MPQL measures four domains of QOL: physical (signs of medical conditions), psychological (emotional and behavioral well-being), social (quality and extent of social interactions), and environmental (freedom and safety in one’s environment). The results of the study indicated a significant improvement in the psychological QOL domain following physiotherapeutic treatment. The social QOL domain declined with the severity of lameness, while the physical QOL, as reported by the owner, declined with the overall criticality of the medical condition, as ranked by the physiotherapist. The results of the study support the recent evidence of a relationship between pain and canine psychological well-being and highlight the importance of investigating psychological and emotional aspects of dogs’ QOL when treating orthopedic and neurological cases with physiotherapy.

Canine Geriatric Syndrome: A Framework for Advancing Research in Veterinary Geroscience

Biological aging is the single most important risk factor for disease, disability, and ultimately death in geriatric dogs. The effects of aging in companion dogs also impose significant financial and psychological burdens on their human caregivers. The underlying physiologic processes of canine aging may be occult, or early signs of aging may be ignored because of the misconception that biological aging is natural and therefore inevitable. The ability to detect, quantify, and mitigate the deleterious processes of canine aging would greatly enhance veterinary preventative medicine and animal welfare. In this paper we propose a new conceptual framework for aging in dogs, the Canine Geriatric Syndrome (CGS). CGS consists of the multiple, interrelated physical, functional, behavioral, and metabolic changes that characterize canine aging as well as the resulting clinical manifestations, including frailty, diminished quality of life, and age-associated disease. We also identify potential key components of a CGS assessment tool, a clinical instrument that would enable veterinarians to diagnose CGS and would facilitate the development and testing of interventions to prolong healthspan and lifespan in dogs by directly targeting the biological mechanisms of aging. There are many gaps in our knowledge of the mechanisms and phenotype of aging in dogs that must be bridged before a CGS assessment tool can be deployed. The conceptual framework of CGS should facilitate identifying these gaps and should stimulate research to better characterize the processes and effects of aging in dogs and to identify the most promising preventative strategies to target these.

The phenotype of aging in the dog: how aging impacts the health and well-being of dogs and their caregivers

Aging is the single most important cause of disease, disability, and death in adult dogs. Contrary to the common view of aging as a mysterious and inevitable natural event, it is more usefully understood as a set of complex but comprehensible biological processes that are highly conserved across species. Although the phenotypic expression of these processes is variable, there are consistent patterns both within and between species.

The purpose of this feature is to describe the patterns currently recognized in the physical and behavioral manifestations of aging in the dog and how these impact the health and welfare of companion dogs and their human caregivers. Important gaps in our knowledge of the canine aging phenotype will be identified, and current research efforts to better characterize aging in the dog will be discussed. This will help set the context for future efforts to develop clinical assessments and treatments to mitigate the negative impact of aging on dogs and humans.

Adaptive spatial working memory assessments for aging pet dogs

Assessments for spatial working memory (SWM) in pet dogs that can detect age-related cognitive deficits in a single session may aid in diagnosing canine dementia and may facilitate translational research on Alzheimer's disease in humans. Adaptive testing procedures are widely used in single-session assessments for humans with diverse cognitive abilities. In this study, we designed and deployed two up-down staircase assessments for SWM in which 26 pet dogs were required to recall the location of a treat hidden behind one of two identical boxes following delays of variable length. In the first experiment, performance tended to decline with age but few dogs completed the test (n = 10). However, all of the dogs that participated in the second experiment (n = 24) completed the assessment and provided reliable evidence of learning and retaining the task. Delay length and age significantly predicted performance supporting the validity of this assessment. The relationships between age and performance were described by inverted U-shaped functions as both old and young dogs displayed deficits in weighted cumulative-scores and trial-by-trial performance. Thus, SWM in pet dogs may develop until midlife and decline thereafter. Exploratory analyses of non-mnemonic fixation strategies, sustained engagement, inhibitory control, and potential improvements for future SWM assessments which adopt this paradigm are also discussed.

Individual and group level personality change across the lifespan in dogs

In humans, age-related changes in personality occur in a non-random fashion with respect to their direction, timing, and magnitude. In dogs, there are still gaps in our knowledge about the detailed dynamics of age-related personality changes. We analysed the personality of 217 Border collies aged from 0.5 to 15 years both cross-sectionally and longitudinally using a test battery, to specify age periods when changes most prominently occur, assess the magnitude of changes, and analyse individual differences in personality change. We found that similar to humans, changes in personality occur unevenly during the dogs’ life course, however, their dynamics seems to be specific for each trait. Activity-independence decreased mostly from puppyhood (0.5–1 years) to adolescence (> 1–2 years), then continued to decrease in a slowing rate. Novelty seeking did not change markedly until middle age (> 3–6 years), then showed a steady linear decrease. Problem orientation increased strongly until middle age then showed no marked changes in later age periods. We also revealed individual differences in personality change over time, and showed that a few individuals with potential age-related impairments significantly affected the general age trajectory of some traits. These results raise caution against the over-generalisation of global age trends in dogs.

Gut Microbiome Composition is Associated with Age and Memory Performance in Pet Dogs

Gut microbiota can crucially influence behavior and neurodevelopment. Dogs show unique similarities to humans in their physiology and may naturally develop dementia-like cognitive decline. We assessed 29 pet dogs' cognitive performance in a memory test and analyzed the bacterial 16S rRNA gene from fecal samples collected right after the behavioral tests. The major phyla identified in the dog microbiomes were Bacteroidetes, Firmicutes, and Fusobacteria, each represented by >20% of the total bacterial community. Fewer Fusobacteria were found in older dogs and better memory performance was associated with a lower proportion of Actinobacteria. Our preliminary findings support the existence of links between gut microbiota, age, and cognitive performance in pet dogs.

A Preliminary Study toward a Rapid Assessment of Age-Related Behavioral Differences in Family Dogs

Over the last few years, several efforts have been undertaken to characterize the aging process in dogs. In the present study, we evaluate a short protocol measuring dogs' cognitive, social, and physical capacities. Our aim was to develop a feasible test battery, with minimal pre-training requirements, no complex devices, and which is set outdoors (i.e., a specific testing room is not needed). As ageing in dogs is usually associated with a decrease in activity, we also assessed the personality trait activity/excitability with a dog personality questionnaire. Four subtests proved sensitive to the dogs' age. In particular, old dogs displayed less approaching and following behaviors toward an unknown but friendly human, showed both less avoidance and interest toward a novel object, looked less at the owner when faced with an unsolvable problem, and performed worse on the short-term memory task. Previous test procedures for investigating age-related changes involve expensive and/or complicated devices and extensive pre-training. The main advantage of the proposed battery is to reduce costs and efforts in veterinary assessments. Further tests in same-breed, large samples and between dogs with mild and severe cognitive impairments will be needed in order to further validate the battery.