Old dogs may teach us a great deal about aging. As dogs get older, some develop learning and memory problems, much like we do. And like people, not all old dogs become impaired. Indeed, some old dogs remain bright and able to learn just as well as younger dogs, although they may be a little slower in reaching high levels of performance.
When an older dog has cognitive problems, we may see them as changes in behavior that can be disruptive to the relationship between owners and pets. For example, an old dog with cognitive problems may forget to signal to go outside, may be up at night and sleep all day, or have trouble recognizing people or other pets in the family. This is similar to a person with Alzheimer’s disease who may have difficulty communicating, disrupted sleep/wake cycles and trouble remembering family and friends.
When aged dogs show cognitive changes not caused by other systemic illnesses, they are related to brain changes that are strikingly similar to people. For example, old dogs develop senile plaques in their brains that are made of a protein that is identical to one that humans produce. This protein, called beta-amyloid, is toxic to cells in the brain.
Unlike mice and rats, old dogs naturally develop significant brain pathology like we see in people. In this way, aging dogs may resemble aging humans in a more natural or realistic way than mice with genetic mutations.
There are many other changes in the brains of people with Alzheimer’s disease that are similar in aging dogs. These include changes in the blood vessels of the brain, the accumulation of damaged proteins and losses in cells, and chemicals that support cells in the brain. These changes may be modified by lifestyle factors.