Dementia is not a specific disease; rather, it is a syndrome. So, first, it is important to understand the meaning of the word ‘syndrome’. A syndrome is a group or set of symptoms that cluster together. A syndrome (e.g., pneumonia) can look the same clinically (with pneumonia, you cough, have a fever, produce sputum, have shortness of breath, fatigue and perhaps chest pain), but have different causes (pneumonia can be caused by tuberculosis, pneumococcal pneumonia, mycoplasma, fungal infections, toxic exposures, etc.) and therefore different treatments, depending on the cause. Additionally, there are predisposing antecedents (vulnerability factors) for pneumonia, such as alcoholism, cystic fibrosis, or hypothyroidism. This means that people with these antecedents are at higher risk than the average person. Finally, there are chemical mediators of pneumonia (the substances or factors that act as the medium of illness) such as white blood cells, hormones (e.g. adrenal steroids), and cytokines (the hormones of the immune system).
When one looks at a syndrome with this ‘Whole’ perspective, things are both more complicated, and more understandable and treatable. Thus, with dementia, we assume that there are a variety of antecedents, mediators, and triggers, which in combination can produce a syndrome we call dementia.
The antecedents of dementia (vulnerability factors) may include genetic factors, such as being a carrier of the APO-E4 genes, or the genes for fronto-temporal dementia. However, carrying the genes themselves does not mean that you will get dementia (I treated a woman who had two copies of the Alzheimer’s risk gene, APO-E4. She was 75 and did not have dementia, but her identical twin sister developed it at age 65). Head injuries (even mild ones that do not produce concussions), chronic inflammation, cardiovascular disease, diabetes, nutritional deficiencies, infectious disease (Chlamydia, H.Pylori, cytomegalovirus, herpes simplex virus 1 and 2, perhaps tick-borne diseases such as Lyme, Bartonella, and other chronic infections), toxic chemical exposures with poor detoxification abilities, high levels of oxidative (free radical) stress, alcohol and substance abuse, all increase vulnerability to the syndrome of dementia. Dementia is highest in incidence in North America and Australia.
The mediators of dementia vary, but overlap with the mediators of many other inflammatory illnesses and therefore include the cytokines. Cytokines are the ‘hormones’ of the immune system. In addition, there are theories that neurotransmitters (such as dopamine, acetylcholine) are also deficient and mediate the syndrome. Free radicals which cause oxidative stress to the mitochondria (energy factories of the cells in the brain) are also mediators, as in the case of chronic or sudden hypoxia, as are hormones (e.g., cortisol, thyroid, insulin), certain proteins (beta-amyloid, tau protein), perhaps some metals, (e.g., aluminum, mercury), radiation therapy (for cancers of the brain), and the apoptosis (programmed cell death) ‘machinery’ of nerve cells.
The triggers of dementia are varied. Usually, they ‘unmask’ the underlying process that has been building for years. In a common scenario, some medical event unmasks dementia. This could be a surgical procedure, starting a new medication, or even an emotional trauma such as the loss of a spouse. In these cases, at first, the problem may look like it has a sudden onset. If it does and it clears quickly, then it is termed a delirium. However, if it continues, despite the removal of the trigger (e.g., a new medication) then by definition, after 6 months, it is called dementia.