Science and Research Questions

Memory impairment is one symptom of Alzheimer's disease, but it is also a symptom of a number of other conditions and disorders so it may be premature to think it is Alzheimer's. For example, stress, depression, vitamin B12 deficiency, interactions between medications (or side effects from a new drug), hypothyroidism (low thyroid hormone levels), and even viral infections can all cause memory problems, confusion, and mood swings. Not that having a few drinks here and there means that one has a drinking problem, but if your father imbibed more often than not, that could also affect his memory over the long-term. The excessive, long term abuse of alcohol has been shown, for instance, to contribute to the development of alcohol dementia, also known as Wernicke-Korsakoff's syndrome or alcoholic encephalopathy, which can cause impairments in memory, vision, and gait. The good news is that many of the aforementioned conditions which can cause memory impairments are treatable, but without a thorough doctor's examination it is not possible to diagnose your father or to begin to treat his memory problem

Alzheimer's disease and prion diseases (such as Creutzfeldt-Jakob disease (CJD)) are similar in the respect that both are characterized by abnormally folded proteins that aggregate in the brain and cause neurodegeneration. In fact, in addition to AD and prion diseases, many of the neurodegenerative diseases – such as Parkinson's disease, fronto-temporal dementia (FTD), and Lewy body disease (LBD) – are sometimes referred to as “conformational disorders” because of the irregular conformation of the misfolded proteins associated with each of the diseases. The main difference between prion diseases and non-prion diseases is the fact that prion diseases are sometimes transmissible, such as through eating animal products contaminated with prion proteins, whereas neurodegenerative diseases such as Alzheimer's and Parkinson's disease are not.

The hallmarks of Alzheimer's disease are brain amyloid plaques (resulting from the accumulation of the protein beta-amyloid) and neurofibrillary tangles (caused by intracellular accumulations of the tau protein). In a healthy brain, these proteins are produced for normal cellular requirements, then broken down and eliminated when they are no longer needed. In Alzheimer's disease, the beta-amyloid (A) fragments and tau proteins do not fold correctly and therefore cannot be broken down. A forms what are called beta-sheet structures and accumulate to form hard, insoluble amyloid plaques surrounding the neurons in the brain, and tau forms neurofibrillary tangles within neurons. Similarly, in CJD and other prion diseases, the diseased prion protein (PrPSc) causes normal harmless prion proteins (PrPC) to adopt a beta-sheet conformation, which is a very stable structure that prompts the abnormally-folded proteins to aggregate and deposit in the brain. The deposits cause cellular damage leading to neuronal death and loss of brain tissue.

Because of the similarities between the prion diseases and AD, some researchers have wondered whether prions are to blame for neurodegenerative diseases such as AD. At the moment, there is no hard evidence to suggest that prions cause Alzheimer's disease or any other non-prion neurodegenerative disorders.

Presenilin-1 (PSEN1) and presenilin-2 (PSEN2) are cellular transmembrane proteins that are involved in amyloid-beta processing. The presenilin proteins form complexes with other proteins, and these complexes (gamma-secretases) function to chop up the amyloid precursor protein (APP) into small protein pieces, such as the amyloid-beta peptide. Mutations in either of the two presenilin genes (PSEN1 or PSEN2) have been linked to cases of early-onset Alzheimer's disease, also known as familial Alzheimer's disease (FAD). Researchers are still trying to determine the mechanism through which mutations in these genes cause the disease. Beta-amyloid is a fragment of a protein that is snipped from its parent protein, amyloid precursor protein (APP).

So what you refer to as “presenilin disease” is actually Alzheimer's disease caused by a mutation in one or both of the two genes. It is an inherited disease and is not contagious. So if your grandfather did “bring something back” from Ireland, it was something that was already present in his genes to be passed on to his descendents, not something he could have contracted while in a psychiatric facility or hospital. The test that was performed on you was probably to look for mutations in the PSEN1 and PSEN2 genes. Your testing negative means that you do not have the presenilin mutations that are associated with the development of FAD.

If you have a family history of familial Alzheimer's disease (FAD) (that is, you have a parent or close relative who developed AD before the age of 65), and are interested in genetic testing, then the best place to start regardless of where you live is your primary care physician. Your doctor can refer you to a genetic counselor and testing facility. The genetic counselor can help you understand what the tests mean, as well as take a family history and decide on the best course of action. The counselor may, for example, want to screen for possible genetic mutations in the affected relative (if he or she is still alive) in addition to screening you.

However, be aware that these genetic tests are not absolute. Even though specific mutations in particular genes have been highly-linked to the development of Alzheimer's disease, inheritance of these mutations does not guarantee that you will definitely get the disease. The environment can also influence your genes, a fact which scientists are aware of but still cannot fully explain.

On the flip side, please also recognize that even if no mutations are found, this does not necessarily mean that you are in the clear. An absence of mutations in Alzheimer disease-associated genes only means that your overall risk of developing AD is equivalent to that of the general population's risk (that is, it is much lower but it still exists because everyone is potentially at risk for developing AD). A genetic counselor will be able to more fully explain the results of such tests to you in greater detail.

Alzheimer's disease may be a cause of seizures; however, not every Alzheimer's disease patients will develop this symptom. If an Alzheimer's patient has a seizure, a careful examination should be carried by a qualified physician. Based on the results, an antiepileptic medication may be selected to help control the seizures.

Several studies have concluded that smoking, particularly in individuals 65 years and older, is associated with an increased risk of Alzheimer's disease, dementia and cognitive decline. This association was not observed for former smokers. Therefore, based on these studies your cousin may be correct: quitting smoking may very well reduce your risk of developing Alzheimer's disease.

A longitudinal Finnish study performed in 2005 found that midlife binge drinking is correlated with an increased likelihood of developing dementia later in life. In the study, persons in their 40s who reported binge drinking (defined by the study as the equivalent of 5 or more beers or 1 bottle of wine consumed at one sitting) at least once a month were found to have an elevated risk of dementia two decades later. And individuals who reported passing out at least twice in one year as a result of drinking too much were at an even higher risk of developing dementia.

Why is this the case? The researchers were not entirely sure, but thought that maybe alcohol's effects on killing brain cells may have something to do with it. College students are also known for binge drinking, but their younger brains may be better able to recover from alcohol's effects. The brain of a middle-aged person simply does not have as much plasticity as the brain of a 20-year-old. Additionally, the authors noted that binge drinking may lead to a higher incidence of falls or accidents resulting in head injuries, which have been linked to an increased risk of developing dementia.

Intriguingly, light to moderate consumption of alcohol (defined as no more than one drink a day) has been associated with beneficial health effects, such as a reduced risk of developing Alzheimer's or other dementias. However, there is very fine line between drinking to promote health benefits and drinking too much and adversely affecting one's health. Therefore, caution is always warranted in these types of findings because alcohol is still a drug, and its excessive and/or chronic use can be detrimental to neuronal cells in the brain. In this case, more of a good thing is not necessarily better. For example, the excessive, long term abuse of alcohol can contribute to the development of alcohol dementia, also known as Wernicke-Korsakoff's syndrome.

Considering that depression is a frequent symptom in Alzheimer's disease and dementia in general, one might suspect that the two conditions (depression and dementia) were related. Indeed, some cognitive symptoms—such as poor concentration, forgetfulness, and impairment in attention—are common to both depression and dementia.

However, the relationship between depression and dementia is complex and mostly unclear. Studies that have attempted to address whether or not depression is a risk factor for the later development of dementia have found conflicting results. For instance, some studies indicate that patients with severe depression or bipolar disease are at a higher risk for developing dementia, while other studies suggest that dementia patients are at a higher risk for depression. The situation is complicated because it is often difficult to determine which condition preceded which, or even if there is a direct link between the two. For example, a diagnosis of dementia, particularly in a patient who is aware of his or her own cognitive decline, can often cause the patient to become depressed. Additionally, underlying medical conditions may give rise to both depression and dementia in conjunction. Conditions such as coronary heart disease, chronic stress, and diabetes can not only lead to depressive symptoms, but are also are risk factors associated with Alzheimer's disease and vascular dementia.

Therefore, if your husband has already been diagnosed with Alzheimer's disease, then your intuition may be right; it is quite possible that his change in attitude could be the result of depression. If, however, your husband has not been diagnosed with Alzheimer's disease or dementia, then his behavior may be the manifestation of any number of medical or psychological ailments, dementia being only one possibility. Whichever the case may be, it would be best to get him checked out by his primary care physician who can perform a thorough physical and psychological evaluation.