The Alzheimer’s disease is a degenerative disease that causes a progressive decline in cognitive function and memory. Gradually, destruction of nerve cells occurs in brain regions related to memory and language. Over time, it is increasingly difficult for the person with memory to remember events, to recognize objects and faces, to remember the meaning of words and to exercise judgment.
In general, the symptoms appear after 65 years and the prevalence of the disease increases sharply with age. However, contrary to popular belief, Alzheimer’s disease is not a normal consequence of aging.
The Alzheimer’s disease is the form of dementia most common in the elderly; it accounts for about 65% of dementia cases. The term dementia includes, in a very general way, health problems marked by an irreversible decrease of mental faculties . Alzheimer’s disease differs from other dementias in that it evolves gradually and mainly affects the short-term memory in its early stages. However, the diagnosis is not always clear and it can be difficult for doctors to differentiate Alzheimer’s disease from Lewy body dementia, for example.
|Is there a difference between normal aging and Alzheimer’s disease?
According Judes Poirier, a researcher at the University Institute Douglas Mental Health, Alzheimer’s can be seen as a form very accelerated aging 55 . In theory, if we lived to 150 or 160 years, it is almost certain that we would all have Alzheimer’s. According to the researcher, for Alzheimer’s to occur in one’s 60s, one must be predisposed to the disease by heredity, lifestyle, and so on.
Prevalence of Alzheimer’s disease
The Alzheimer’s disease affects about 1% of people aged 65 to 69, 20% of those aged 85 to 89 years and 40% of those 90 to 95 years 1 . In Canada, about 500,000 people have Alzheimer’s disease or a related disease.
It is estimated that 1 in 8 men and 1 in 4 women will suffer during their lifetime. As women live longer, they are more likely to be infected one day.
Due to the prolongation of life expectancy , this disease is becoming more common. It is estimated that within 20 years the number of people will double in Canada.
The Alzheimer’s disease is characterized by the appearance of lesions very specific that gradually invade the brain and destroy its cells, the neurons . The neurons of the hippocampus, the region that controls memory, are the first affected. We do not know yet what causes the appearance of these lesions.
Dr : Alois Alzheimer, a German neurologist, gave its name to the disease in 1906. He is the first to describe these brain injuries during autopsy of a dead woman with dementia. In his brain, he had observed abnormal plaques and tangles of nerve cells now considered the main physiological signs of Alzheimer’s disease.
Here are the 2 types of damage that occur in the brains of people with:
- Excessive production and accumulation of beta-amyloid proteins in certain areas of the brain. These proteins form plaques , called amyloid plaques or senile plaques, that are associated with neuron death.
- The “deformation” of some structural proteins (called Tau proteins ). The way the neurons are entangled is then modified. This form of injury is called neurofibrillary degeneration.
To these lesions is added inflammation that contributes to altering the neurons. There is still no treatment that can stop or reverse these pathological processes.
Causes of Alzheimer’s disease
The causes of Alzheimer’s disease are not known. In the vast majority of cases, the disease appears due to a combination of risk factors. The aging is the main factor. Risk factors for cardiovascular diseases (hypertension, hypercholesterolemia, obesity, diabetes, etc.) also seem to contribute to its development. It is also possible that infections or exposure to toxic products play a role in some cases but no formal proof has been obtained.
The genetic factors also play an important role in causing the disease. Thus, some genes may increase the risk of being affected, although they are not directly the cause of the disease. Indeed, researchers have discovered that about 60% of people with Alzheimer’s disease carry the Apolipoprotein E4 or ApoE4 gene. Another gene, SORL1, also seems to be often involved. However, many individuals carry these genes and will never have the disease and, conversely, some people without these genes can develop the disease.
There are also hereditary forms of the disease but they account for less than 5% of cases. Only 800 families have been listed in the world. Children with a parent with Alzheimer’s disease in hereditary form have 1 in 2 risk of having the disease themselves. Symptoms of the familial form appear early, sometimes before age 40. However, even if several members of the same family are affected by this disease, this does not necessarily mean that it is the hereditary form.
Evolution of the disease
The Alzheimer’s disease evolves over several years and its progression varies greatly from one person to another. We now know that the first lesions appear in the brain at least 10 to 15 years before the first symptoms 2 .
These usually appear after the age of 60 years. On average, once the disease starts, life expectancy is 8 to 12 years. The older the disease, the more it tends to get worse quickly. When it occurs around the age of 60 or 65, life expectancy is about 12 to 14 years; when it occurs later, life expectancy is only 5 to 8 years. It is currently impossible to stop the evolution of the disease.
- Light stage. Of memory loss occurs occasionally. Short-term memory that is, the ability to retain recent information (a new phone number, the words in a list, etc.), is the most affected. People with Alzheimer’s disease try to overcome their difficulties by using reminders and their loved ones. Mood changes and slight disorientation in space can also be observed. The person has more trouble finding their words and following the thread of a conversation.At this point, it is not certain whether it is Alzheimer’s disease. Over time, symptoms may remain stable or even decrease. Diagnosis is confirmed if memory problems increase and other cognitive functions deteriorate (language, object recognition, complex motion planning, etc.);
- Moderate stage. The memory problems are amplified. The memories of youth and middle age become less accurate but are better preserved than immediate memory. It is increasingly difficult for people to make choices; their judgment begins to be altered . For example, they are gradually becoming more difficult to manage their money and plan their daily activities. Disorientation in space and time becomes more and more obvious (difficulty remembering the day of the week, birthdays …). Affected people have more and more difficulty expressing themselves verbally;Between the moderate and advanced stages, unusual behavioral problems sometimes arise: for example, aggression, atypical, foul language or a change in personality traits.
- Advanced stage (or terminal). At this point, the patient loses his autonomy . A permanent monitoring or accommodation in a nursing home becomes necessary. Psychiatric problems may occur, including hallucinations and paranoid delusions, aggravated by severe memory loss and disorientation. Sleep problems are common. Patients neglect their personal hygiene, become incontinent and struggle to feed themselves. If left unattended, they can roam for hours.
The person can die of another disease at any stage of Alzheimer’s. However, in its advanced stages, Alzheimer’s disease becomes a deadly disease , such as cancer. Most deaths are caused by pneumonia caused by difficulty swallowing. Patients may allow saliva or some of what they eat or drink into their airways and lungs. This is a direct consequence of the progression of the disease. Alzheimer’s disease is now the 7 th leading cause of death in Canada, according to Statistics Canada.
Diagnostic of Alzheimer’s disease
|Warning: it is not because you forget your keys, an appointment or the name of someone who has Alzheimer’s disease. This occasional forgetfulness is normal at any age and is usually related to inattention. If they are common, they can mask a depressive or anxious state. Only tests done by a doctor can determine if one is suffering from a real memory disorder. Often, family members are worried about their loved ones and ask for a consultation.|
To make the diagnosis , the doctor uses the results of several medical examinations. First, he questions the patient to find out more about how his memory loss and the other difficulties he experiences in everyday life are manifested. Of tests to assess cognitive faculties are made, as the case of vision tests, writing, memory, problem solving, etc. In case of memory impairment, even with attention, the patient’s test performance will be abnormal.
In some cases, various medical tests may be performed to rule out the possibility that the symptoms are attributable to another health problem (vitamin B12 deficiency, malfunction of the thyroid gland, stroke , depression, etc.).
If deemed necessary, the physician may also advise the patient to undergo a brain imaging test(preferably an MRI, magnetic resonance imaging) to observe the structure and activity of different areas of his brain. Imaging can highlight the loss of volume (atrophy) of certain areas of the brain, characteristic of degeneration of neurons.
|The hope of early diagnosis
There is a great deal of research going on around the world to create tools to diagnose disease at an earlier stage, when memory loss is mild or even before the onset of symptoms. In fact, the disease sets in insidiously long before the symptoms of dementia appear. Several tests, still experimental, show that it is possible to obtain an early diagnosis: memory tests, brain imaging tests or blood tests 6 or cerebrospinal fluid .
Symptoms of Alzheimer’s disease
- Alteration of short-term memory (name of new people encountered, events of previous hours or days, etc.);
- Difficulty retaining new information;
- Difficulty performing familiar tasks (locking doors, taking medications, finding things, etc.);
- Difficulty in language or aphasia (difficulty finding words, speech less understandable, use of invented or inappropriate words);
- Difficulty following a conversation, a path of thought;
- Difficulty or inability to plan (meals, budget, etc.);
- Gradual loss of sense of direction in space and time (difficulty finding the day of the week, remembering the season, birthday, time of day, unable to find his way. ..);
- Disorders of gestures or apraxia (difficulties to write, to button his jacket, to use everyday objects, to wash …);
- Difficulty in grasping abstract notions and reasoning;
- Difficulty in recognizing objects, the faces of relatives ( agnosia );
- Progressive impairment of long-term memory (loss of childhood memories and adulthood);
- Changes in mood or behavior, sometimes aggression or delirium;
- Personality changes;
- Gradual loss of autonomy.
People at risk
- People aged 60 and over. The age is the main risk factor: the risk of developing the disease doubles every 5 years from 65;
- The women (because they live longer than men);
- People who have a parent, brother or sister with Alzheimer’s disease. Their risk of being reached in turn is increased by 10% to 30% compared to the rest of the population;
- People whose parent has the inherited familial form of Alzheimer’s disease. Children with an affected parent have a 50% chance of having the disease themselves;
- People of Hispanic and African American origin are more likely to have the disease (up to 2 times more) .
Most important factors
- Systolic hypertension;
- High cholesterol;
- Diabetes poorly controlled by medication
- Serious head trauma with loss of consciousness (occurring, for example, in boxers);
- Personal history of depression.
|Can we prevent?|
|Currently, there is no clearly effective way to prevent Alzheimer’s disease. Some measures, however, seem to help preserve cognitive abilities and reduce the risk of developing the disease. Here are the most studied.|
|Preventive measures at the research stage|
It is possible to reduce the risk of suffering from Alzheimer’s disease by intervening medically, paying attention to lifestyle habits (healthy eating, exercise, etc.) and avoiding certain risk factors, such as high blood pressure. , diabetes, hypercholesterolemia and smoking.
The hormone replacement in women at the age of menopause or anti-inflammatory drugs intake (such as aspirin and ibuprofen) could provide some protection against Alzheimer’s disease, according to studies population, but the prospective studies on this subject have proved negative.
For general advice on the key elements of a healthy diet , see our How to Eat Well? and Food Guides.
Various studies have been conducted to find out if a particular diet could prevent Alzheimer’s by delaying aging. Here are 3 avenues currently explored:
This diet could help prevent Alzheimer’s disease. A prospective study conducted in 2006 among 2,258 Americans indeed indicates that people whose diet is closest to the Mediterranean diet are less likely to suffer from Alzheimer’s disease. The same team of researchers also noted that this type of diet reduces mortality associated with the disease.
These observations were confirmed in 2009 by a study conducted on a cohort of 1,796 French people aged 65 and over. According to the study, the Mediterranean diet is associated with a lower cognitive decline Scientists explain in part its protective effect on neurons by its high content of antioxidants. Eicosapentenoic acid (EPA), an omega-3 fatty acid found in fish, appears to be particularly protective ;
The subjects who consumed the most calories and had a genetic background that predisposed them to this disease (they were carriers of the ApoE4 gene) were more affected than those who absorbed the least calories. Studies in animals 13 suggest that caloric restriction increases brain neuronal resistance to Alzheimer’s disease, Parkinson’s disease and stroke. It also limits the normal neuronal loss associated with age ;
The benefit of regular physical activity for the prevention of dementia and cognitive decline has been shown by several epidemiological studies and recent clinical trials. One of them showed that a moderate exercise program at home (3 sessions of 50 minutes a week, or 20 minutes of walking a day, for 24 weeks), allowed to improve the cognitive performance of people with memory problems 16 . Moreover, adults practicing physical activities regularly appear less frequently affected by Alzheimer’s disease.
Several recent prospective studies have shown that people regularly engaged in stimulating mental activities (reading, learning, memory games, etc.), whatever their age, are less likely to suffer from dementia 18 . For example, the case of the famous Nun Study, an epidemiological study on aging and Alzheimer’s disease 15. This study has been conducted since 1986 among 678 nuns of the School Sisters of Notre Dame, a community where the average age is 85 years and many sisters are over 90 years old. In these nuns, who lead a healthy life, have a good diet and little stress, the rate of Alzheimer’s disease is significantly lower than that of the general population. Significantly, many of them are highly educated and carry out intellectual activities that are very demanding for their age.
Thus, keeping an active mind throughout one’s life promotes the maintenance and growth of connections between neurons, which would delay dementia. In addition, some believe that a high level of education helps to make it easier to pass the cognitive tests used to diagnose Alzheimer’s disease. This would make up for the effects of the disease longer.
Several ongoing trials attempt to evaluate the effects of regular mental training in people with onset of Alzheimer’s disease. However, it appears that the effects of this type of exercise are less marked when cognitive decline began.