As man's best friend, dogs contribute to our social well-being throughout our lifespan. However, understanding how our canine companions age is also contributing to our medical well-being.

It turns out an aging dog has a natural development of cognitive decline that parallels some of the human dementias associated with aging. This includes the deposits of beta-amyloid in the brain and neural tissue that is considered the hallmark of Alzheimer's disease in humans.

In the 1990s, the National Institutes of Health began funding projects to better understand the normal and pathologic cognitive age-related changes in canines. Researchers had already recognized that many animals develop the amyloid deposits, and the effort to study the process included a colony of 40 aging beagles at the University of California Davis.

The dogs were monitored and lived a normal lifestyle, advancing naturally to an older age, which averaged around 16 years. Dogs were only euthanized if there was an unusual level of pain or disease. The study used dog-related memory tests, and one was a swimming activity with platforms.

The researchers found a genetic component to which dogs had greater cognitive impairment and pathology on autopsy. They also found that changes did not occur before the dogs reached age 10.

There continue to be canine populations under study to follow the course of aging. Pet owners can even enroll their dogs into studies related to pharmaceutical treatments and aging.

Beagle brains contain us to better understand age-related dementia. Beagle retinas are also a means to follow the progression of a naturally occurring dementia in beagles.

The most recent Association of Research in Vision and Ophthalmology held in Seattle had reports of retinal structure changes that parallel human studies. With imaging of retinal amyloid deposits using polarization properties, researchers found the extent of deposit changes correlated to the severity of the canine dementia.

Other research showed fluorescent labeling of amyloid could be imaged noninvasively, and this is a tool for studying the progression of pathology. This supports early canine work that had used Thioflavin-S and curcumin to highlight retinal amyloid deposits. That work had observed how similar the deposits were to humans with Alzheimer's disease.

Using the eye and retina to identify biomarkers of Alzheimer's disease has been suggested as a noninvasive means to follow the disease progression. Canine models are demonstrating how to do this. Beagle brains under study are showing us the potential of man's best friend to contribute to our health as we age.