Abstract
Background
In elderly people, dementia and urinary tract dysfunction often exacerbate one another. Aging dogs also suffer cognitive decline but the relationship between cognitive decline, soiling behaviors, and urinalysis abnormalities has not been explored.
Hypothesis/Objectives
Soiling behavior is associated with urinalysis abnormalities and cognitive performance in aging dogs.
Animals
Eighty-four client-owned dogs enrolled in a longitudinal cohort study of aging.
Methods
In this prospective observational study, dogs were evaluated biannually with free-catch urinalysis, owner-completed Canine Dementia Scale (CADES), and a cognitive test battery. Mean age at enrollment was 12.77 years ± 1.91, 53 were female spayed, 29 male neutered, and 1 female and 1 male intact. Mixed-effects and generalized linear mixed models were used to assess the associations between urinalysis variables and cognitive test performance.
Results
Of 231 urinalyses, 19 showed pyuria, 14 hematuria, 11 bacteriuria, and 194 proteinuria. Urine specific gravity (USG) ranged from 1.005 to 1.056 and decreased significantly with age (P < .001). Soiling scores ranged from 0 to 25, and were associated with increasing age (P < .001) and decreasing USG (P < .001). In multivariable models, age and USG remained significant predictors of soiling. Higher soiling scores were associated with poorer performance on inhibitory control (P < .001) and detour tasks (P < .001).
Conclusions and clinical importance
Increased soiling behavior was linked to USG and executive function. Abnormal urinalysis findings were less frequent than expected. Soiling behavior in aging dogs might not exclusively reflect urinary tract or systemic disease and could be an indicator of cognitive decline.
Keywords: canine cognitive dysfunction syndrome, canine gerontology, cognitive impairment, executive function, soiling behavior
Introduction
Aging in people is associated with a decline in many physiological systems, including the lower urinary tract and cognition.1,2 Urinary tract infections (UTIs) in older adults are one of the most common bacterial infections leading to hospitalization and sepsis.3,4 Dementia further increases the risk of UTI, such that people living with dementia are more than twice as likely to be diagnosed with UTIs in the emergency department.5 Acute cognitive decline, including delirium, has been attributed to UTI in older adults; however, the relationship between bacteriuria and UTI with cognitive deterioration is complex and remains uncertain and controversial.4,6–8 Asymptomatic bacteriuria is highly prevalent in elderly populations and is frequently overtreated, as antimicrobial therapy has not been shown to improve outcomes in the absence of urinary-tract–specific symptoms.9,10 Additionally, with age, the kidneys lose the ability to concentrate urine, resulting in a decrease in urine specific gravity (USG), which could facilitate bacterial proliferation.9
The lifespan of dogs has increased due to improved veterinary standards of care, which has also contributed to higher recognition of age-related conditions, such as canine cognitive dysfunction syndrome (CCDS).10–12 The proportion of owner-reported behavioral signs consistent with CCDS increases with age, ranging from 18.8% in dogs aged 11-13 years to 67.3% in dogs aged 15-17 years, based on questionnaires.11,13 The behavioral manifestations of cognitive decline in dogs include altered social interactions, spatial disorientation, disrupted sleep–wake cycles, changed activity levels, anxiety, and house soiling.14,15 One challenge in assessing this constellation of behaviors is that non-neurologic conditions can produce similar signs.16–20 House soiling is an example of this, with urinary tract disease, systemic disorders, and mobility loss all potentially causing this behavior. While abnormal urinalysis findings, such as pyuria, hematuria, and bacteriuria, are reportedly common in aging people with cognitive decline,3,4,21 there is a paucity of longitudinal data on urinalysis findings in aging dogs. Similarly, data are lacking on the frequency with which soiling behavior in aging dogs is due to cognitive decline vs underlying urinary tract pathology.10,14 Finally, it is unclear whether canine UTIs can impair cognitive performance in a manner similar to that encountered in humans.22
In this exploratory longitudinal study, we aimed to evaluate the relationship between cognitive decline and changes in urinalysis variables in senior and geriatric dogs and to explore whether house soiling behavior was correlated with cognitive dysfunction or urinary tract disease. We hypothesized that cognitive decline in dogs is associated with an increase of urinalysis abnormalities and poor performance on cognitive tests.
Materials and methods
Data were included from a prospective, longitudinal, observational study conducted at North Carolina State University, College of Veterinary Medicine. Clinically stable client-owned elderly dogs with a fractional lifespan23 of ≥ 0.75 with no acute illness, and physical ability to participate in mobility and cognitive tests, were enrolled. The protocol was reviewed and approved by the North Carolina State University Institutional Animal Care and Use Committee (IACUC # 18-109; 21-303; 24-255) and all owners reviewed and signed a written informed consent form.
Each dog was evaluated biannually, with the protocols described in detail in previous manuscripts.19,24–30 A free-catch urine sample was submitted for urinalysis before cognitive tests. Urine cultures were not part of the study protocol. Owners were asked to complete the Canine Dementia Scale (CADES31), from which the CADES soiling score was derived (Table S1). Dogs performed a battery of cognitive tasks assessing attention, executive function, working memory, and social cue interpretation (Figure 1).24,32,33
Figure 1.
Schematic of cylinder tasks. (A) Inhibitory control: The dog must inhibit a direct approach and retrieve the reward by going to either side openings of the transparent cylinder. (B) Detour task: With the dog’s preferred side from the previous task blocked, the dog must detour to the other side to access the reward.
For the current study, we included data from visits that had urinalysis, cognitive testing, and a completed CADES questionnaire. The primary outcomes were CADES soiling score, representing owner-reported soiling behavior, and performance on cognitive tests. Predictors included age, sex, and urinalysis parameters, including USG, pyuria (>5 WBC/HPF), hematuria (>5 RBC/HPF), bacteriuria (>trace), and proteinuria (>15 mg/dL). If on day 1 of a scheduled study visit, a dog showed clinical signs consistent with UTI (Table S2) and urinalysis findings of bacteriuria and pyuria ± hematuria or proteinuria, the visit was discontinued, and cognitive tests were not performed due to the risk of introducing antibiotic-resistant infection in the cognitive testing room. The lack of cognitive testing meant these visits did not meet inclusion criteria. Owners were advised to follow up with their primary veterinarian.
Statistical analyses were completed using JMP Student Edition 18 (SAS Institute Inc., Cary, NC). Descriptive statistics were prepared for age and weight, sex, urinalysis parameters, CADES soiling scores, and cognitive testing outcomes. Mixed-effects models assessed associations between predictors and cognitive test results, with Dog ID included as a random effect to account for repeated measurements. For associations involving CADES soiling score as the outcome, we used generalized linear mixed models with a Poisson distribution and log link, with Dog ID included as a random effect. Predictors with P ≤ .10 in univariable analyses were entered into multivariable models; statistical significance was defined as P < .05. Cross-sectional analyses used baseline observations only. Sex differences in urinalysis abnormalities were evaluated using logistic regression. Details on methods, including cognitive task protocols, CADES questionnaire, and statistical analysis, are provided in the Appendix.
Results
Study cohort
Eighty-eight dogs were enrolled in the Longitudinal Study of Neuroaging between January 2019 and May 2025. Four dogs were excluded because they did not meet the inclusion criteria for the current study; data from 84 dogs were included in the present analysis (Figure 2). All enrolled dogs completed at least one study visit, and 60 of 84 dogs (71.4%) completed 2 or more visits, resulting in a total of 268 observations across study visits included in mixed-effects models (Table 1).
Figure 2.
Flow diagram of the dataset for the current analysis from the parent longitudinal aging cohort. Analyses were restricted to completed study visits that included urinalysis, cognitive testing, and a completed CADES questionnaire. Abbreviation: CADES = Canine Dementia Scale.
Table 1.
Study cohort characteristics at enrollment.
| Number of dogs | 84 dogs |
|---|---|
| Number of visits (total) | 268 visits |
| Number of visits with UA done | 231 visits |
| Age (years) at enrollment (mean ± SD) | 12.77 ± 1.91 |
| Fractional lifespan (mean ± SD) | 0.99 ± 0.14 |
| Median weight at enrollment (Q1-Q3) | 17.8 (8.9-25.2) kg |
| Sex | |
| – Female (spayed) | 53 (63%) |
| – Female (intact) | 1 (1%) |
| – Male (neutered) | 29 (35%) |
| – Male (intact) | 1 (1%) |
| Breed size category | |
| – Small (<10 kg) | 37 (44%) |
| – Medium (10-25 kg) | 13 (16%) |
| – Large (>25 kg) | 34 (40%) |
| Median number of visits per dog | 2 (1-10) |
| Dogs with ≥ 3 visits | 43 (49%) |
Values are mean ± SD or median (IQR) unless otherwise noted.
Abbreviations: UA, urinalysis; SD, standard deviation.
On 6 occasions, involving 6 individual dogs, physical signs (polyuria [n = 2], pollakiuria [n = 1], gross hematuria [n = 3], and urinary incontinence [n = 2]) and urinalysis (the presence of pyuria [n = 6], bacteriuria [n = 6], hematuria [n = 4], and proteinuria [n = 5]) raised clinical suspicion for urinary tract infection. These dogs did not perform cognitive testing at that visit and so their data from that visit were not included. Owner of 3 of these dogs withdrew them from the longitudinal cohort study permanently due to recurrent urinary tract infections after these events, and they did not contribute to additional visits.
Of the 84 dogs, 53 were spayed females, 1 was an intact female, 29 were castrated males, and 1 was an intact male. There were 30 mixed-breed dogs; the remaining 54 were purebreds, comprising the following breeds: Labrador Retriever (n = 7), Beagle (n = 4), Golden Retriever (n = 4), American Staffordshire Terrier (n = 2), Jack Russell Terrier (n = 3), Shih Tzu (n = 3), Basset Hound (n = 2), Border Collie (n = 2), Dachshund (n = 2), German Shepherd Dog (n = 2), Siberian Husky (n = 2), Australian Cattle Dog (n = 1), Australian Shepherd (n = 1), Bernese Mountain Dog (n = 1), Border Terrier (n = 1), Brittany Spaniel (n = 1), Brussels Griffon (n = 1), Cardigan Welsh Corgi (n = 1), Cairn Terrier (n = 1), Chihuahua (n = 1), Chow Chow (n = 1), Cockapoo (n = 1), Cocker Spaniel (n = 1), Foxhound (n = 1), German Shorthaired Pointer (n = 1), Great Dane (n = 1), Irish Setter (n = 1), Maltese (n = 1), Miniature American Shepherd (n = 1), Pembroke Welsh Corgi (n = 1), Plott Hound (n = 1), and Pomeranian (n = 1).
The mean age at admission to the study was 12.77 ± 1.91 years (mean ± SD), corresponding to a mean fractional lifespan (FLS) of 0.99 ± 0.14. Across all study visits, the mean age was 13.25 ± 1.74 years, and the mean FLS was 1.04 ± 0.13.
Urinalysis variables
A total of 231 urinalyses were performed, of which, excluding proteinuria, 30 (23 dogs) were abnormal. Among these, 19 (18 dogs) exhibited pyuria, 14 (10 dogs) hematuria, and 11 (8 dogs) bacteriuria. Protein was detected in 194/231 (84%) of samples. It was reported as negative 37 times, trace (15 mg/dL) 73 times, 1+ (30 mg/dL) 101 times, 2+ (100 mg/dL) 14 times, and 3+ (500 mg/dL) once.
Longitudinal logistic mixed models showed no significant association between sex and the presence of pyuria (P = .46), hematuria (P = .73), or proteinuria (P = .95). The odds of bacteriuria were significantly higher in females (P = .03; Table 2).
Table 2.
Results of univariable logistic mixed-effects models evaluating the association between sex and urinalysis abnormalities in aging dogs. Odds ratios (ORs), 95% CIs, and P values are shown.
| UA abnormality | Odds ratio (F vs M) | 95% CI | P value | Pseudo-R 2 |
|---|---|---|---|---|
| Pyuria | 1.28 | 0.66-2.45 | .46 | 0.0011 |
| Hematuria | 1.11 | 0.62-1.99 | .73 | 0.0015 |
| Bacteriuria | 2.45 | 1.11-5.41 | .03 | 0.0006 |
| Proteinuria | 1.02 | 0.54-1.94 | .95 | 0.0216 |
Dog ID was included as a random effect to account for repeated observations. Sex was modeled as a binary explanatory variable (female vs male), and urinalysis abnormalities were treated as binary outcomes. Pyuria was defined as > 5 WBC/HPF, hematuria as > 5 RBC/HPF, bacteriuria as > trace bacteria, and proteinuria as > 15 mg/dL.
Abbreviations: HPF, high-power field; OR, odds ratio; RBC, red blood cell; WBC, white blood cell.
Across the 231 urinalyses, the median USG was 1.027 (range, 1.005-1.056). A cross-sectional analysis of age at admission (n = 84 dogs) and corresponding USG showed that older dogs had significantly lower USG than younger dogs (r2 = .07, P = .01; Figure 3A). In mixed-effects models that incorporate repeated observations across study visits, increasing age was significantly associated with lower USG (P < .001; β = −0.0018; 95% CI, −0.0027 to −0.0009; Figure 3B). Sex was not a significant predictor in either model.
Figure 3.
Visual representation of the association between USG and age in senior and geriatric dogs. (A) Cross-sectional relationship between age at enrollment and USG, with regression line and 95% CI (r2 = 0.07, P = .01). (B) Relationship between age and USG across all study visits, with regression line and 95% CI (pseudo-R2 = 0.44, P < .001). Abbreviation: USG = urine specific gravity.
International Renal Interest Society (IRIS) staging was available for 134 visits, with 111 classified as stage 1 and 23 as stage 2. IRIS stage did not change significantly with age (P = .92), but it showed a significant association with USG in univariable analysis (P = .02, pseudo-R2 = .01), which remained significant after adjusting for age in a multivariable model (P = .03, pseudo-R2 = .05).
Soiling behavior
Canine Dementia Scale soiling scores ranged from 0 to 25, with a median of 3. Univariable analyses are summarized in Table S3. Variables with P ≤ .10 in univariable analyses were included in multivariable models. In the final multivariable generalized linear mixed model, each additional year of age was associated with a higher expected CADES soiling score (β = 0.54; 95% CI, 0.45-0.62; P < .001; Figure 4A) corresponding to an estimated 71% increase in the expected CADES soiling score for each additional year of age. Similarly, each 0.001 increase in USG was associated with an approximately 2.4% lower expected CADES soiling score (β = −0.024; 95% CI, −0.036 to −0.012; P < .001; Figure 4B). Pyuria (P = .28) and bacteriuria (P = .63) were not significantly associated with soiling score (Table 3). There was also no significant difference in soiling scores between females and males (P = .58).
Figure 4.
Visual representation of associations between CADES soiling scores with age and USG in senior and geriatric dogs. (A) Relationship between age and soiling score across all study visits, with regression line and 95% CI (pseudo-R2 = 0.52, P < .001). (B) Relationship between USG and soiling score across all visits, with regression line and 95% CI (pseudo-R2 = 0.5, P < .001). Abbreviations: CADES = Canine Dementia Scale; USG = urine specific gravity.
Table 3.
Results of multivariable generalized linear mixed-effects models with a Poisson distribution and log link evaluating associations between CADES soiling score and age, USG, pyuria, and bacteriuria in aging dogs.
| Outcome | Predictor | Estimate (β) | 95% CI | P value |
|---|---|---|---|---|
| CADES Soiling score | Age (per year) | 0.54 | 0.45 to 0.62 | <.001 |
| USG (per 0.001 increase) | −0.024 | −0.036 to −0.012 | <.001 | |
| Pyuria (present vs absent) | −0.17 | −0.49 to 0.14 | .28 | |
| Bacteriuria (present vs absent) | −0.19 | −0.97 to 0.59 | .63 |
Poisson generalized linear mixed models with log link were used. Dog ID was included as a random effect to account for repeated observations. Variables with P ≤ .10 in univariable analyses were considered for inclusion in multivariable models; only variables retained in the final model are shown. Age and USG were analyzed as continuous variables, whereas pyuria and bacteriuria were binary variables.
Abbreviations: CADES, Canine Dementia Scale; USG, urine specific gravity.
Cognitive tests
Summary statistics for cognitive tests are provided in Table 4. Univariable and multivariable analyses of associations between individual cognitive test outcomes, age, sex, urinalysis abnormalities, USG, and soiling score are shown in Table 5 and Table S4. In univariable analyses, sustained gaze, inhibitory control, detour task performance, and working memory were significantly associated with CADES soiling score (Table S4). In multivariable analysis, sustained gaze duration decreased by approximately 3.8 s for each additional year of age (β = −3.81; 95% CI, −5.27 to −2.36; P < .001), whereas CADES soiling score was not independently associated with sustained gaze performance (P = .29). After adjusting for age, each one-point increase in the CADES soiling score was associated with a 1.13 percentage-point decrease in inhibitory control performance (β = −1.13; 95% CI, −1.70 to −0.57; P < .001). Each one-point increase in the CADES soiling score was also associated with a 0.84 percentage-point decrease in detour task performance (β = −0.84; 95% CI, −1.56 to −0.13; P = .02; Table 5). Hematuria was associated with a higher percentage of correct inhibitory control trials in univariable analysis (P = .04), and this association persisted after adjusting for age, CADES soiling score, pyuria, and bacteriuria (P = .05). Working memory performance decreased by approximately 6.5 s for each additional year of age (β = −6.53; 95% CI, −10.37 to −2.69; P < .001), while CADES soiling score was not significantly associated with performance (P = .15). Sex was not a significant predictor in any of the cognitive test outcomes (Table S4).
Table 4.
Summary statistics of cognitive test outcomes.
| Cognitive test | Observations (n) | Median (Q1-Q3, range) |
|---|---|---|
| Inhibitory control (% correct) | 232 | 88 (75-100, 0-100) |
| Detour (% correct) | 232 | 50 (12.5-75, 0-100) |
| Average eye gaze (seconds) | 251 | 14.0 (6.1-25.3, 0-90) |
| Pointing cue (% correct) | 209 | 91.7 (75-100, 0-100) |
| Working memory (seconds) | 214 | 20 (6-60, 0-120) |
Values are median (Q1-Q3) and range. Sample sizes vary because not all cognitive tests were completed by every dog at every visit.
Table 5.
Results of multivariable linear mixed-effects models evaluating associations between cognitive task performance and age, CADES soiling score, and urinalysis variables in aging dogs. Regression coefficients (β), 95% CI, and P values are shown.
| Outcome | Predictor | Estimate (β) | 95% CI | P value |
|---|---|---|---|---|
| Inhibitory control | Age (per year) | −1.23 | −3.60 to 1.15 | .31 |
| Soiling score (per 1-point increase) | −1.13 | −1.70 to −0.57 | <.001 | |
| Hematuria (present vs absent) | 14.54 | 0.11 to 28.96 | .05 | |
| Pyuria (present vs absent) | 0.56 | −12.08 to 13.20 | .93 | |
| Bacteriuria (present vs absent) | 7.10 | −11.24 to 25.45 | .45 | |
| Detour task | Age (per year) | −7.06 | −9.84 to −4.29 | <.001 |
| Soiling score (per 1-point increase) | −0.84 | −1.56 to −0.13 | .02 | |
| Bacteriuria (present vs absent) | 11.74 | −7.06 to 30.55 | .22 | |
| Sustained gaze | Age (per year) | −3.81 | −5.27 to −2.36 | <.001 |
| Soiling score (per 1-point increase) | −0.17 | −0.50 to 0.16 | .29 | |
| Pyuria (present vs absent) | 5.14 | −0.10 to 11.28 | .10 | |
| Proteinuria (present vs absent) | 0.91 | −2.54 to 4.35 | .60 | |
| Working memory | Age (per year) | −6.53 | −10.37 to −2.69 | <.001 |
| Soiling score (per 1-point increase) | −0.72 | −1.71 to 0.26 | .15 |
Dog ID was included as a random effect to account for repeated observations. Variables with P ≤ .10 in univariable analyses were considered for inclusion in multivariable models; only variables retained in the final models are shown. Age and CADES soiling score were analyzed as continuous variables, whereas pyuria, hematuria, bacteriuria, and proteinuria were binary variables.
Abbreviation: CADES, Canine Dementia Scale.
Discussion
In this cohort of client-owned aging companion dogs enrolled in a longitudinal aging study, increasing age was significantly associated with lower USG and higher soiling scores. Urinalysis findings consistent with urinary tract disease, excluding mild proteinuria, were infrequent in our cohort. Contrary to our hypothesis, pyuria, bacteriuria, and proteinuria were not significantly associated with the CADES soiling score or cognitive test performance. In contrast, we found that dogs with worse soiling behavior performed significantly worse in cognitive tasks that involved executive function. Moreover, urine concentrating ability, reflected by USG, showed significant longitudinal changes with age and was significantly associated with soiling behavior reported by owners.
Urine SG decreased with age in our cohort of aging dogs and was also significantly associated with higher CADES soiling scores. However, it did not predict cognitive test outcomes. The association between increasing age and lower USG parallels previously reported changes in urinary parameters in both humans and dogs,9,34 reflecting reduced renal concentrating ability with age. More dilute urine could reflect age-related changes in renal concentrating ability and could contribute to urinary accidents through mechanisms that remain incompletely understood. Consistent with previous reports, lower USG was associated with higher IRIS stage in our study, supporting its place as a practical marker of renal concentrating ability. These findings suggest that reduced USG might warrant further investigation within the broader context of aging in dogs.35,36
The overall prevalence of abnormal urinalyses in our study was lower than anticipated (13% of samples). Although cognitive testing was not performed in dogs that exhibited clinical signs and urinalysis findings suggestive of UTI this only excluded 6 visits, which, if included, would only increase prevalence of abnormalities to 15% of samples. One possible explanation is that aging causes atypical or blunted immune responses, known as immunosenescence. In older adults, diminished leukocyte recruitment and cytokine signaling can result in reduced pyuria even in the presence of infection.21,37 Immunosenescence in aging dogs increases vulnerability to infection and chronic inflammation, potentially leading to under detection of urinary tract disease on standard urinalysis.38 Urine cultures were not routinely performed and so the rate of occult infections could not be determined.
Sustained gaze duration, an indicator of attention, and working memory were more closely linked to age than to soiling score or urinary variables. This suggests that attention and memory deficits in aging dogs involve cognitive domains that might not be directly related to soiling behavior. Domain-specific patterns of cognitive decline have been strongly emphasized in human medicine and could be the next step in investigating cognitive decline in dogs.39,40
By contrast, the inhibitory control and detour tasks were significantly associated with CADES soiling score. These 2 tasks assess key aspects of executive function in dogs. Inhibitory control tests the dog’s ability to suppress a prepotent response.33 The detour task builds on this by requiring spatial problem-solving and cognitive flexibility.33 Poor performance on these tasks indicates deficits in executive functions, including impulse control, response inhibition, and flexible problem-solving. These deficits are well-documented features of human Alzheimer’s disease and are increasingly recognized in dogs with CCDS.11,12 The association between higher soiling scores and poorer performance on these tests suggests that elimination in the home might reflect not just disorientation but also impaired decision-making, or failure of impulse control. Notably, prior CCDS cohorts report that loss of housetraining is uncommon in borderline/mild disease and becomes more frequent with greater impairment, consistent with house-soiling emerging relatively later in the course.11,15 This relationship highlights the use of house soiling behavior as an indicator of more profound cognitive impairments in aging dogs.
We also observed that dogs with hematuria performed significantly better in inhibitory control; however, this finding should be interpreted with caution. The small number of instances of hematuria compared to the total number of urinalyses in our study might indicate that this is a spurious finding and does not have a biological underlying reason.
Working memory performance, which relies on short-term information retention, was primarily influenced by age rather than soiling score or urinalysis findings, consistent with prior reports that memory decline follows rather than precedes deficits in executive function.41,42
Pointing cue performance, representing social and communicative processing, was not significantly associated with any urinary parameter, age, or the house soiling score. This is consistent with an extensive cross-sectional analysis testing truncation vs compression models of canine cognitive aging, in which gesture-following (human pointing) showed age-related maintenance or improvements relative to other tasks.43
This study had several limitations. Because the sample size was determined by the available cohort rather than by a priori power calculation, the study might have been underpowered to detect small associations between urinalysis parameters and cognitive outcomes. The low number of abnormal urinalyses and low prevalence of pyuria, hematuria, and bacteriuria in our cohort limited our ability to robustly evaluate their relationship with cognitive decline. In addition, visits in which urinalysis findings were suggestive of urinary tract infection were excluded from cognitive testing, which might have further reduced the opportunity to detect associations between urinary abnormalities and cognitive outcomes. Additionally, the CADES soiling domain encompasses both urination and defecation, which prevented us from distinguishing between urinary and fecal soiling behaviors. A more targeted behavioral instrument that differentiates urinary accidents due to cognitive decline in aging dogs would improve phenotyping in future studies. Additionally, urine cultures were not performed, which restricted our ability to confidently differentiate between infection, inflammation, and contamination in free-catch samples. The study cohort was biased toward healthier dogs, as individuals with unstable medical conditions were not recruited, and dogs requiring intensive medical management could be less likely to be enrolled in a longitudinal research cohort. The study group also contained a higher proportion of female dogs than male dogs, reflecting volunteer recruitment characteristics within the parent longitudinal aging cohort. Although sex-related differences in aging or lifespan could potentially contribute to this imbalance, there is currently insufficient evidence to support this explanation in dogs. Despite these limitations, our findings suggest an association between cognitive function in one domain and soiling behavior in aging dogs.
In this longitudinal cohort, increasing age was associated with lower USG, whereas pyuria, hematuria, and bacteriuria were uncommon. House soiling was associated with advancing age, lower USG, and poorer performance on executive-function tasks, but not with urinalysis abnormalities. These findings suggest that soiling behavior among aging companion dogs enrolled in this longitudinal study does not exclusively reflect lower urinary tract disease; and in many cases could represent a potential clinical indicator of cognitive dysfunction or loss of learned elimination behaviors. Alternatively, lower USG and age-related changes in urinary physiology might contribute to urinary accidents independent of cognitive decline. Although causality cannot be established from this exploratory analysis, the observed relationship between soiling behavior and executive dysfunction warrants further investigation.
Supplementary Material
Abbreviations
- CADES
Canine Dementia Scale
- CKD
chronic kidney disease
- FLS
fractional lifespan
- IC
inhibitory control
- IRIS
International Renal Interest Society
- OR
odds ratio
- USG
urine specific gravity
- UTI
urinary tract infection
Appendix: Materials and methods
Study cohort
Client-owned dogs enrolled in the Longitudinal Study of Neuroaging in Dogs, conducted at the North Carolina State University, College of Veterinary Medicine, were included.25,26,29,40 To be enrolled, dogs were required to be clinically stable with no acute illness, and capable of participating in mobility, cognitive and physical assessments. Dogs with a fractional lifespan of ≥ 0.75, calculated using a formula based on breed-specific height and weight, were included.23 Dogs were excluded if they had comorbidities that interfered with cognitive testing (eg, blindness, inability to ambulate independently). Stable chronic conditions like osteoarthritis and chronic kidney disease were permitted. The protocol was reviewed and approved by the North Carolina State University Institutional Animal Care and Use Committee (IACUC # 18-109; 21-303; 24-255) and written informed consent was obtained from all dog owners.
A.2. Study design
Data used for the present analysis were generated in a prospective, longitudinal, observational study at North Carolina State University, College of Veterinary Medicine, assessing aging in dogs across multiple domains, including physical health, cognition, sensory function, mobility, muscle mass, and urinary tract health. Each dog underwent a 3-day evaluation every 6 months, and protocols have been described in detail in previous manuscripts.20,25–31 On day 1, dogs received a complete physical, neurological, and orthopedic examination. Complete blood cell counts and serum biochemistry panels were performed once a year. A free-catch midstream urine sample was collected and submitted to the Clinical Pathology Laboratory at the North Carolina State University, College of Veterinary Medicine for a urinalysis at each visit. Urine culture was not included in the study protocol. If, on day 1 of a scheduled study visit, urinalysis findings were consistent with urinary tract infection, and the dog showed clinical signs suggestive of UTI (Table S2), cognitive tests were not performed to avoid the risk of introducing antibiotic-resistant infection in the cognitive testing room, which is a shared research space. Following these findings, owners were advised to seek clinical evaluation and treatment with their primary care veterinarian, where a urine culture would have been done if clinically indicated. As such, those visits were discontinued.
Mobility and postural stability assessments, as well as functional hearing tests, were also performed. Owners completed the Canine Dementia Scale (CADES32) questionnaire along with others related to general health (study-specific), pain (LOAD,37 CBPI38), quality of life (adapted CORQ39,40), sleep quality (Snore3.020), cognition (CCDR41 in addition to CADES), and frailty.42,43 On day 2, a battery of cognitive tests was administered.25,33,34 These tests included the sustained gaze, the cylinder test, working memory, and pointing cue. The sustained gaze test assessed attention span 3 times, by measuring the duration of voluntary eye contact between the dog and the experimenter using a treat. The cylinder tasks are tests of executive function (Figure 1). To evaluate inhibitory control, dogs were presented with a clear cylinder that holds a visible treat inside. Rather than attempting to reach the treat directly (straight through the transparent barrier of the cylinder), dogs needed to navigate to the open ends to retrieve the reward. Performance was scored as the percentage of successful trials completed without touching the transparent surface. In the detour task, the dog’s preferred side of the cylinder was blocked by a transparent barrier, requiring the dog to detour to the opposite side’s opening to retrieve the treat. This was also scored as percentage of successful trials. In the working memory task, memory retention was tested by delaying access to a baited container after a visible placement of the reward and was recorded as the duration of time (in seconds) the dog could remember which container held the treat. The pointing cue assessed whether dogs could interpret a social gesture to find a hidden food reward, scored as the percentage of correct attempts to find the food reward. On day 3, each dog underwent electrophysiologic testing of retinal function and hearing. Longitudinal data were collected and managed using a REDCap (Research Electronic Data Capture) electronic data capture tool hosted at (blinded).44,45 This study did not involve human research; therefore, the Institutional Review Board (IRB) approval was not required.
The number of dogs included in this analysis was determined by the size of the longitudinal cohort, and therefore, no a priori sample size calculation was performed for this analysis. The inclusion criterion for the current study on urinalysis abnormalities, house soiling, and cognitive performance was the availability of at least one study visit during which urinalysis, cognitive testing, and a completed CADES questionnaire were available. For each visit that was used in the analysis, the dog’s age, sex, breed, weight, fractional lifespan, and any notable findings from the physical examination were recorded.
A.3. Owner-reported soiling behavior
Soiling-related behavioral changes were assessed using the house soiling domain of the CADES,32 a validated 17-item owner questionnaire (Table S1, Supporting information). Canine Dementia Scale includes 4 domains: spatial orientation, social interaction, sleep–wake cycles, and house soiling. For this study, only the house soiling domain, consisting of the final 5 items of the questionnaire, was analyzed. These items reflect owner-observed changes in urination and defecation habits. The soiling score ranges from 0 to 25, with higher scores indicating more severe soiling behavior.
A.4. Urinalysis and renal function
Urine specific gravity was recorded. Protein was measured by dipstick analysis and reported in mg/dL. Urinalysis abnormalities were defined as pyuria (>5 WBC/HPF), hematuria (>5 RBC/HPF), bacteriuria (>trace), and proteinuria (>15 mg/dL).21,35,36 Any urinalysis with at least one of these abnormalities was considered abnormal. Chemistry panels were performed annually and were evaluated to determine an IRIS stage.46
A.5. Statistical analysis
All statistical analyses were performed using JMP Student Edition 18 software (SAS Institute Inc, Cary, NC). Descriptive statistics were prepared for age and weight at admission, sex, urinalysis abnormalities and USG, CADES soiling scores, and individual cognitive testing outcomes across the entire study period.
We used mixed-effects models for the primary study outcomes. Associations involving individual cognitive test outcomes were evaluated using linear mixed-effects models. Because the CADES soiling scores, which represent house soiling behavior, were non-negative and contained a large proportion of zero values, associations involving the CADES soiling score as the outcome were evaluated using generalized linear mixed models with a Poisson distribution and log link. Dog ID was included as a random effect to account for repeated observations within individuals. Age and urinalysis variables (urine specific gravity, pyuria, hematuria, and bacteriuria) were included as fixed effects. For cognitive test outcomes, the CADES soiling score was also included as a fixed effect. Each predictor was first assessed in univariable models, and variables with P ≤ .10 were considered for inclusion in multivariable models. Statistical significance was defined as P < .05.
Sex differences in urinalysis abnormalities (pyuria, hematuria, bacteriuria, and proteinuria) were assessed using logistic mixed-effects models with Dog ID included as a random effect to account for repeated observations.
Contributor Information
Shaghayegh Rafatpanah Baigi, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Chin-Chieh Yang, Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Montréal, QC, Canada.
Alejandra Mondino, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Gilad Fefer, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Wojciech K Panek, Department of Clinical Sciences & Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States.
Beth C Case, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Emily H Griffith, Department of Statistics, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, NC, United States.
Margaret E Gruen, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Natasha J Olby, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States.
Author contributions
Shaghayegh Rafatpanah Baigi (Formal analysis, Investigation, Methodology, Visualization, Writing—original draft), Chin-Chieh Yang (Data curation, Investigation, Writing—review & editing), Alejandra Mondino (Data curation, Investigation, Writing—review & editing), Gilad Fefer (Data curation, Investigation, Writing—review & editing), Wojciech Krzysztof Panek (Data curation, Investigation, Writing—review & editing), Beth Case (Data curation, Investigation, Project administration, Writing—review & editing), Emily Griffith (Formal analysis, Supervision, Writing—review & editing), Margaret E. Gruen (Methodology, Supervision, Writing—review & editing), and Natasha Olby (Conceptualization, Data curation, Formal analysis, Funding acquisition, Methodology, Project administration, Supervision, Writing—review & editing)
Conflicts of interest
The authors declare no conflicts of interest.
Funding
Dr Kady M. Gjessing and Rhanna M. Davidson Distinguished Chair in Gerontology.
Off-label antimicrobial declaration
The authors declare no off-label use of antimicrobials.
Institutional animal care and use committee or other approval declaration
Approved by the North Carolina State University Institutional Animal Care and Use Committee (IACUC #18-109; #21-303; #24-255).
Human ethics approval declaration
The authors declare human ethics approval was not needed.
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