Aging is a normal and natural process that occurs in all living beings and involves a series of changes at different levels. These changes include modifications in the individual’s own biology, but also in psychological and social aspects. All these changes are associated with an increase in the risk of developing certain diseases in which advanced age seems to play a relevant role. In this context, neurodegenerative diseases form part of the group of diseases in which the risk of suffering from them increases notably with age.
It goes without saying that advanced age is a variable strongly associated with the risk of developing Alzheimer’s disease. However, it is necessary to clarify that neither age nor aging is the cause of Alzheimer’s disease.
Cognitive impairment, the same as Alzheimer’s disease?
In Alzheimer’s disease, a series of events occur that ultimately result in neuronal dysfunction and death and the consequent development of the central symptoms of the disease (e.g., memory loss). In Alzheimer’s disease, a number of “abnormal” proteins accumulate in the brain that appear to play a key role in neuronal death. The exact mechanisms that explain why some people have these protein aggregates and develop Alzheimer’s disease, but other people do not, are currently unknown. This means that we do not know the exact cause of Alzheimer’s disease.
Dementia itself is not a disease, but a set of symptoms that can be found in multiple diseases such as Alzheimer’s disease. Dementia is characterized by the presence of cognitive impairment severe enough to cause interference with normal, independent functioning in activities of daily living. Therefore, dementia is something that happens in Alzheimer’s disease and in many other diseases that associate cognitive impairment. This means that any disease that associates such severe cognitive impairment as to incapacitate the person entails dementia, but not all dementia or cognitive impairment means having Alzheimer’s disease.
Initial cognitive impairment and dementia in the context of Alzheimer’s disease usually have a rather characteristic appearance, where one type of memory impairment usually predominates along with other symptoms. Despite these generalities, sometimes Alzheimer’s disease has a distinct or atypical appearance where behavioral, language or visual perception disorders may predominate instead of memory problems. The characterization of these distinctive features of Alzheimer’s disease is done by neuropsychological examination of patients. That is, a series of tests and examinations are used to enable the neuropsychologist to determine what type of impairment the person has, how severe it is and whether the profile is compatible with Alzheimer’s disease. In parallel to the neuropsychological profile, Alzheimer’s disease is accompanied by a series of changes in brain structure and functioning that can be studied using brain imaging techniques. In addition, we can now also measure in plasma and cerebrospinal fluid the levels of certain abnormal proteins that accompany Alzheimer’s disease.
Precisely because Alzheimer’s disease has a characteristic appearance, any form of cognitive impairment or dementia other than Alzheimer’s disease has long been attributed to age and aging. In this context, these cases have often been referred to as senile dementia or age-related dementia. This concept of senile or age-associated dementia has been used in those cases where the imaging tests or neuropsychological profile is not typical of Alzheimer’s disease. This concept necessarily implies assuming age or aging as the cause of dementia and, therefore, normalizes and accepts that getting older can lead to the implicit development of dementia without any other cause. Today we know that this idea is categorically incorrect and that, in fact, the concept or diagnosis of senile dementia does not exist.
Other neurodegenerative diseases
Beyond Alzheimer’s disease there are many other neurodegenerative diseases, whose causes lie in mechanisms similar or not to those found in Alzheimer’s disease. All these other diseases have sufficiently specific clinical, neuropsychological and cerebral characteristics for us to establish a precise diagnosis. These diseases include frontotemporal dementia, corticobasal degeneration, dementia with Lewy bodies, vascular dementia, cognitive impairment associated with Parkinson’s disease and many other entities. In addition, it is always worth considering that cognitive impairment is not always due to neurodegenerative causes, but that other conditions, sometimes potentially treatable, may be behind the development of progressive dementia. Among these other causes, we can include infections, metabolic syndromes, vascular causes, autoimmune causes, exposure to certain toxins and certain drugs, and so on.
For all these reasons, cataloging people as suffering from “senile dementia” implies not defining a diagnosis, nor establishing the cause, nor having considered other explanations, nor being able to establish a prognosis or an accurate treatment. That is, to label a person with a diagnosis of senile dementia is to misdiagnose.
Aging involves changes at many levels, but not necessarily cognitive impairment or dementia. Therefore, when a person begins to show cognitive changes we should not attribute these symptoms to age, but we must delve into the causes that may be behind, reach an accurate diagnosis and thus be able to provide appropriate treatments.