Retrogenesis is a term that has been applied in recent years to dementia — Alzheimer’s disease in particular — to describe the progression by which a person loses skills. A great deal of work on this concept has been done by Dr. Barry Reisberg and others over the last 30 years.
When a child grows and develops, from infancy onward, it passes through a series of well-documented landmarks or developmental milestones. These have been studied in detail, and it is possible to determine how far along the child is in her development by observing and measuring certain behaviors, and comparing them to landmarks demonstrated by other children. An example of an early landmark is the ability to hold her head up independently, and these progress through the ability to sit up, to eat solid food, to walk, to speak, to perform complicated mathematical operations, and so on through to adulthood. It is possible for a person who is familiar with these landmarks to predict what stage a child will progress through next, and if she is developing at an expected rate.
Dr. Reisberg and others have been able to demonstrate that persons with certain forms of dementia, including Alzheimer’s disease, lose skills in the reverse order that they are developed by children. For example, a person with dementia may lose the power of abstract thought, and later the ability to dress herself, followed by the ability to feed herself independently, and so on. Certain behaviors exhibited by the individual have been shown to correlate with specific stages of dementia, so that it is possible to predict what skills she will have difficulty with next. This applies not only to physical function, but also to thought processes.
There are occasions, however, in which a person with dementia will not show a pattern of regression that is totally in line with what would be expected. This can usually be credited to other disease processes that might be present in the individual. For example, if she has severe rheumatoid arthritis, she might lose the ability to walk independently sooner than might be expected.
The similarities between the acquisition of skills in childhood and the deterioration of those same skills in a person with dementia is observable not only in their order, but also in the temporal sequence. Most children take about 20 years to develop from infancy to young adulthood. Likewise, the interval from the time a person shows the first clinical indications of Alzheimer’s to the time they become totally dependent on others usually spans about 20 years.
It is possible to relate behaviors observable in a person with dementia to a specific developmental stage exhibited by a child. This allows health care professionals to conjecture, on the basis of observable (and measurable) behaviors, those which are not readily apparent with regards to linguistic and emotional factors. For instance, if an individual displays grooming skills equivalent to those typically seen in a 3-year-old child, it might also be extrapolated that she would understand language at the same level. As a result, a caregiver might do well to keep instructions simple, and refrain from using too many abstract concepts.
There are some important points to remember, however, when considering the process of retrogenesis. For one thing, while the person with dementia may show a regression in physical/functional, cognitive, and linguistic skills, she will not show an actual physical regression. Therefore, while it is quite common for a person with Alzheimer’s, who is at the end stage (and near death) to show a grasp reflex such as might be seen in an infant, it is important to remember that the individual is still a 6-foot-tall man who worked all his life as a farmer — and quite likely has a very firm grip. It is equally as important to remember that these individuals need to be accorded the same respect that would ordinarily be given to any adult. Even if she may have the linguistic skills of a 5-year-old, it would be wrong to “talk down” to her.
It is not known why this retrogenesis occurs with Alzheimer’s disease and other dementias. It has been theorized that the myelin, or white matter covering the axonal processes that extend out from the nerve is injured. This myelin is produced continually through the life of the individual. It may be that the myelin which develops later deteriorates first, with the older myelin breaking down later on in the process.