Alzheimer’s Disease | Definition, Causes, Diagnosis & Treatment

Alzheimer’s Disease (AD) is the most common form of dementia worldwide (60-70% of all dementia cases) and is a progressive neurodegenerative disorder. Though around 10-15% of cases are genetic, the vast majority of cases are sporadic and attributed to many risk factors. There is, at present, no cure or disease-modifying treatments for Alzheimer’s disease.

Key Symptoms: Initially mild cognitive impairment and subtle memory loss of recent events before progressing to more severe cognitive impairment with profound amnesia, in addition to personality, behavioural and motor changes, which ultimately lead to death.

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Alzheimer's Disease

What is Alzheimer’s Disease?

Alzheimer’s disease (AD) accounts for around 60% of all dementia cases worldwide, making it the most common form of dementia. Alzheimer’s is a progressive neurodegenerative disease with symptoms gradually worsening over a period of a few years. As with most dementias, Alzheimer’s symptoms usually begin with subtle difficulties in remembering recent memories before gradually progressing to more severe symptoms (outlined below).

Alzheimer’s is generally a disease of advanced age and becomes more common over the age of 65. However, developing dementia is not a normal or healthy part of ageing. In rarer cases, Alzheimer’s can affect individuals much younger (between 30-40 years old) with approximately 5% of cases occurring in people under the age of 65. Though the disease is the same, the causes of early-onset Alzheimer’s are usually slightly different to what is known as sporadic Alzheimer’s disease.

Alzheimer’s Disease Signs & Symptoms

As Alzheimer’s disease is a progressive neurodegenerative disease, symptoms are initially subtle and mild, before gradually worsening over a period of several years. The onset, progression severity and speed, as well as time to death varies significantly between affected individuals, depending on the exact cause and mechanism involved.

The symptoms of Alzheimer’s disease can be broken down into three stages:

1. Early-Stage Symptoms:

  • Subtle memory loss of the most recent events e.g. forgetting a recent conversation or event, as well as repetitive questioning and the inability to select certain words in conversations
  • Subtle mood changes or behavioural changes which are not normal for the individual – these can manifest as increased anxiety and confusion
  • Other cognitive symptoms may include increased difficulty in making decisions and becoming more hesitant in certain things

It is important to note that misplacing items or forgetting things occasionally is a normal part of ageing – however, when this becomes routine, is often a sign of dementia.

2. Middle-Stage Symptoms:

  • Worsening of memory loss which progresses to forgetting names of people close to them, as well as forgetting the faces of loved ones
  • Mood changes become more profound with increased anxiousness, frustration and signs of repetitive or impulsive behaviours
  • Depressive symptoms alongside anxiety – including loss of motivation
  • In some cases, there may be signs of delusions and hallucinations

At this stage, activities of daily living become impaired and patients usually require some level of care and assistance, especially as the disease progresses.

3. Late-Stage Symptoms:

  • All of the above symptoms become more severe, behavioural, mood, motor and cognitive – with increased distress for both the patient and caregiver
  • Violence towards caregivers is not uncommon and patients can become suspicious of those around them, including loved ones
  • Due to feeding issues, severe weight loss can occur in some patients

Brain Changes in Alzheimer’s Disease

There are two key pathological hallmarks of Alzheimer’s: beta-amyloid plaques, which form within brain tissue and around vessels (cerebral amyloid angiopathy) and tangles within neurons of a protein called tau. Together, these contribute to the neurodegeneration (death of neurons and synaptic connections) which leads to the overall shrinkage (atrophy) of brain matter within the cortex and hippocampus. The death of neurons and atrophy of key brain regions correlates with disease progression and symptom severity.

Alzheimer’s Disease Diagnosis

Short-term memory loss or subtle, early symptoms of dementia may be overlooked or attributed to medications, stress, depression and anxiety, which can mimic AD. However, if these symptoms gradually worsen and persist, then that may be a sign of dementia.

Unfortunately, there is no single test for diagnosing Alzheimer’s or any other dementia. If your GP is concerned that the symptoms may be due to dementia, they may refer you to a specialist – usually a neurologist and/or psychiatrist at a dedicated memory clinic. A neurologist will assess for physical signs of dementia, whereas a psychiatrist will evaluate the cognitive symptoms. A neurologist may also recommend a CT or MRI scan of the brain to assess any brain pathology to rule-out or confirm diagnosis.

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