Advances in dementia in pets
by Jenny Alonge
Cognitive dysfunction is now more prevalent in aging pets. In dogs, 28% of 11- to 12-year-olds and 68% of 15- to 16-year olds are affected, while 36% of 11- to 21-year-old cats are affected. Plus, incidence increases with age. The following article details recent research that investigated this concerning condition.
Sleep and cognition in aging dogs
As part of an ongoing trial on canine aging and cognition, North Carolina State University researchers performed electroencephalography (EEGs) on geriatric dogs to determine if brain-wave readings during sleep correlated with cognitive decline. Details include:
- Subjects — Researchers evaluated 28 geriatric dogs, who included 17 females and 11 males.
- Cognitive evaluation — The dogs’ owners completed the Canine Dementia Scale (CADES) questionnaire, and the researchers performed cognitive testing to objectively evaluate different cognition domains, including attention, working memory, and executive control.
- Polysomnographic studies — Researchers performed polysomnographic studies, including simultaneous recordings of EEG, electrical activity of the muscles (EMG), eye movements (EOG), and electrocardiogram (ECG). They affixed four electrodes to each dog’s skull, and made the recordings in two sessions. The first session helped acclimate the dog to the surroundings and electrodes, and the second session recorded brain activity during a two-hour sleep period.
- EEG measurements — The EEG measured the dogs in four sleep stages (i.e., wakefulness, drowsiness, rapid eye movement [REM], and non-REM [i.e., the deep sleep state prior to REM]).
- Results — Dogs with higher CADES scores spent less time in non-REM and REM sleep. In addition, when evaluating different cognition domains, problem-solving abilities showed a positive correlation with time spent in non-REM and REM sleep and a negative correlation with time awake.
This study established important baselines for identifying canine cognitive decline, and the researchers hope that their work can lead to early diagnosis and intervention for geriatric dogs with cognitive decline.
Physical activity and cognition in older dogs
As part of the Dog Aging Project, researchers investigated the correlation between physical activity and cognitive decline in senior dogs. Details include:
- Hypothesis — Researchers hypothesized that higher physical activity levels would be associated with better cognitive dysfunction scores and a lower dementia prevalence.
- Subjects — The study evaluated 11,574 dogs enrolled through the Dog Aging Project and found that 287 of the dogs scored more than the clinical threshold for canine cognitive dysfunction (CCD).
- Assessment — Dog owners completed the Health and Life Experience Survey (HLES), which provides information about dog and owner demographics, as well as the dog’s physical activity, environment, behavior, diet, medications, preventives, and health status. The owners also completed the Canine Social and Learned Behavior Survey (CSLB), which is based on the Canine Cognitive Dysfunction Rating (CCDR) Scale, and measures what the owner reports about their dog’s cognitive function. Dogs receive a score from 16 to 80, where higher scores indicate poorer cognitive function.
- Results — Physical activity was significantly negatively associated with three metrics of cognitive dysfunction, including current sign severity, how much the condition worsened over six months, and whether a dog had reached a clinical CCD threshold. Other relevant findings included:
- Medical conditions, such as endocrine disorders, neurological conditions, orthopedic impairments, periodontal disease, cancer, and kidney disease were associated with cognitive dysfunction.
- Higher CSLB scores were associated with sensory impairments, including loss of smell, hearing, and eyesight.
- A positive association was noted in dogs taking daily neuroprotective supplements, such as fish oil, and cognitive dysfunction severity.
- Dogs who had a history of training were less likely to exhibit cognitive decline.
- Subjects — The study included six companion dogs 10 to 16 years of age.
- Canine cognitive dysfunction diagnosis — The dogs had a CCDR score greater than or equal to 50 and had exhibited neurobehavioral dysfunction during the previous six months. Researchers performed diagnostics to rule out other potential biological causes, such as systemic infection, pain, intracranial mass, renal failure, polypharmacy, diabetes, or endocrine disorders.
- Baseline — Researchers used a wearable device attached to the dog’s collar to record the dog’s baseline physical activity for one week.
- Procedure — During weeks two to four, three procedures were performed on the dogs during a single general anesthetic period. These included skin biopsy, MRI of the brain and implantation of fixed fiduciary screws into the skull.
- Processing — The skin sample was processed for the production of autologous skin-derived neuroprecursors (SKNs).
- Reevaluation — At 10 to 14 days post procedure, the dog’s primary care provider repeated the CCDR, and researchers considered this score the pre-therapeutic reference baseline score. The dog’s spatial memory was also assessed in the Canine Sand Maze.
- Hippocampal microinjection — Approximately four to five weeks post procedure, the anesthetized dogs were injected with autologous SKN cells into their hippocampus. The dogs received oral levetiracetam for 48 hours pre-operatively and one week post-surgery to reduce postoperative seizure activity risk.
- Assessments — Follow-up veterinary assessments were performed at one, three, and six months post surgery, and then annually for life. Repeat spatial memory assessment was repeated at three and six months.
- Results — Eighty percent of the dogs responded therapeutically, defined as improvement beyond the Reliable Change Index of the CCDR (i.e. > 5 points), 60% dropped below the CCD diagnostic threshold, and 33% experienced a full syndromal remission, considered a score that improved greater than 43%.
Sources used in this story include:
"Autologous skin-derived neural precursor cell therapy reverses canine Alzheimer dementia-like syndrome in a proof of concept veterinary trial." Stem Cell Research & Therapy. June 2022.
"Sleep and cognition in aging dogs. A polysomnographic study." Frontiers in Veterinary Science. April 2023.
"Associations between physical activity and cognitive dysfunction in older companion dogs: results from the Dog Aging Project." GeroScience. April 2023.
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