Nutrition Can Help Improve the Effect of Cognitive Dysfunction in Older Dogs

10/07/2014

article header for senior dogsOld dogs sleep more than when they were younger. Everyone knows that. But when senior dogs become disoriented in the familiar surroundings of their home or act confused by people who have cared for them their entire lives, it can be unsettling.

Imagine your dog seemingly undergoing a personality change that includes forgetting housetraining skills, being less alert, and having a mixed up sleep-wake pattern. These behavioral changes are attributed to a condition common in older dogs known as cognitive dysfunction syndrome (CDS). 

Studies show that 20 to 30 percent of dogs over 7 to 9 years of age show signs of cognitive dysfunction. In dogs over 14 years of age, it increases to 68 percent of dogs.

“Canine aging is known to affect learning and various types of memory,” says Karen Overall, V.M.D., Ph.D., DACVB. “In dogs, cognitive dysfunction syndrome is usually diagnosed based on a history of disorientation, alterations to social and interactive behaviors, changes in locomotor behavior and sleep-wake cycles, and loss of housetraining. In the beginning, dogs may have only slightly altered sleep cycles and appear anxious. Social-interactive behaviors may first appear as increased neediness but then change to aloof disengagement.”

Understanding the cause of CDS involves examining the cognitive and molecular  changes that occur in the brains of aging dogs. “The cumulative burden of oxidative stress over time is the most common topic examined in brain aging,” Dr. Overall says. “It appears to affect all major classes of molecules involved in neurotransmission.”

Among the changes that occur are physical atrophy in certain areas of the brain, increases in oxidative damage and decreases in mitochondrial energy metabolism. Free radicals play an important role in aging, and the brain is particularly susceptible to the effect of free radicals because it has a high rate of oxidative metabolism, a high content of lipids, or fats, and a limited ability to regenerate.

Dietary or supplemental antioxidants are known to decrease the damaging effects of free radicals. Some studies have shown improved memory or cognitive performance in dogs fed antioxidant-enriched diets or supplements combined with behavioral enrichment in senior dogs.

DHA (docosahexaenoic acid), a long-chain polyunsaturated omega-3 fatty acid, plays an important role in normal neural functions. Several studies have shown a decrease of DHA in the aging brain. Supplementation with fish oil results in improved neural development and learning ability in young dogs, but more research is needed to learn whether there is a benefit from DHA in canine cognitive disorders.

In addition to potential benefits from antioxidants and long-chain omega-3 fatty acids, alternative brain energy sources may help offset cognitive decline. The brain accounts for only 2 to 3 percent of body weight, but uses 25 percent of the body’s glucose. Glucose is believed to be the primary energy source of neurons in the brain and central nervous system, though glucose metabolism becomes less efficient with aging. Thus, alternative sources of energy are needed to support the high-energy requirements of the brain.

Lactate and ketones are alternate energy sources that can easily be used by neural tissue. Medium-chain triglycerides (MCTs) stimulate ketone production, which also crosses the blood-brain barrier and provides an energy source for neural tissue.

“The reduction of brain glucose metabolism is a common feature associated with aging, a process that starts around middle age and may be partially responsible for age-dependent cognitive decline,” says Purina Research Scientist Yuanlong Pan, Ph.D., who specializes in studying healthy aging.

In a Purina study, researchers wanted to learn if dietary supplementation with MCTs could improve cognition in aging dogs by providing the brain with ketones as an alternative energy source. Ketone bodies are a natural endogenous energy source mainly produced by the liver from mobilization of endogenous body fat and used by tissues, such as the brain, heart, kidney and muscle.

Older dogs were randomly assigned to two groups based on cognitive tests. They were fed a control diet or a diet containing 5.5 percent MCTs for eight months. During the feeding trial, dogs were tested on their learning ability, memory and attention.

“Dogs fed the MCT diet showed significantly better performance on most of the tests than control dogs,” Dr. Pan says. “In summary, this study shows that dietary MCT supplementation can significantly increase blood ketone concentrations and improve cognitive function in old, healthy dogs.”

Owners of older dogs can take heart in knowing that diets enriched with alternative brain energy sources, such as MCTs, may help offset their dogs’ negative behavioral changes. Combined with providing an interactive environment and activities, you may see a return to the behavior of your dog’s younger days. 

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