Definition: According to DSM-IV, dementia is characterised by multiple cognitive deficits that are severe enough to cause significant impairment in social or occupational functioning. These deficits must show evidence of decline from previous levels of functioning, include memory impairment, and at least one other cognitive disturbance, including aphasia (disturbed language), apraxia (unable to execute tasks or movements), agnosia (loss of recognition of objects, people, sounds, shapes or smells) or a disturbance in executive functioning. The highest prevalence of diagnosis is above age 85. Dementia is classified as being progressive, static, or remitting. The subtypes of dementia are listed below.


Dementia of the Alzheimer's type (DAT) —deterioration of higher cortical function (this is the most common form)
Vascular dementia —one form is multi-infarct dementia (MID), which is secondary to atherosclerosis
Dementia due to other general medical conditions, including infection with the human immunodeficiency virus (HIV), traumatic brain injury, Parkinson's disease, Huntington's disease, Pick's disease, Creutzfeldt-Jakob disease, normal-pressure hydrocephalus,
hypothyroidism, brain tumour, and vitamin B deficiencies
Substance-induced persisting dementia due to drug or alcohol abuse, medication, or toxin exposure

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, accounting for approximately 60% of cases of dementia. AD is defined as memory loss with at least one other area of cognitive impairment (e.g., language, attention, orientation, self-monitoring, judgment, motor skil, inability to perform daily activities). Memory loss usually begins at about age 65 and slowly
progresses to severe impairment over 8 to 10 years, but it may present earlier and advance at a faster or slower rate; early onset of Alzheimer's disease heralds a particularly aggressive form. Approximately 20% of cases of Alzheimer's are actually attributable to another disease process; definitive diagnosis can only be confirmed at time of autopsy.

Aetiology/Risk factors:
Major causative factors and risk factors that can contribute to the incidence of Alzheimer’s disease include the following:
• Family history of Alzheimer's disease and other dementias
• Down's syndrome
• Head trauma (especially with loss of consciousness)
• Other factors sometimes associated with dementia include age (onset at age 65 and above); late maternal age; history of depression; strokes, especially with a history of hypertension; alcohol or drug abuse; and history of CNS infection.
• Advanced age (20% to 40% with fully developed symptoms of AD are over age 85)
• Female > male—results of studies are not conclusive, however; the greater incidence in women may be related to their tendency to greater longevity
• Longstanding hypertension
• History of head trauma—association is not definitive
• Lower educational level—association is not definitive, but may be related to the observation that learning is necessary to stimulate growth of neurons
• Trisomy 21 (Downs syndrome)
• Elevated homocysteine
• Western diet and lifestyle (less common in Asia and Africa, increases as people move to west)
• Exposure to electromagnetic fields (unproven)
• Other factors speculated to contribute to the development of AD include infections (e.g., herpes virus 1 or Chlamydia pneumonia
and, possibly, prions)

Signs and Symptoms:
•Memory loss—eventually includes loss of personal information and inability to recognise family (CT or MRI may distinguish AD from multi-infarct dementia or other causes)
• Language deterioration (aphasia)
• Motor activities impairment (apraxia)
• Impaired ability to recognise objects (agnosia)
• Inability to think abstractly, i.e., to plan, initiate, sequence, monitor, and stop complex behaviour (disturbances in executive functioning)
• Temporal and spatial disorientation—may lead to aimless wandering
• Muscle rigidity and shuffling gait—resembles Parkinson's disease without a tremor
• Depression and suicidal behaviour
• Hallucinations, delusions, psychosis; the beliefs expressed are often quite concrete (e.g., false accusations of spousal infidelity, accusing a friend of stealing, being frightened of their own image)
• Aggression, agitation, anxiety, restlessness
• Withdrawal, apathy, and social passivity may alter nate with belligerence and loss of inhibitions
• Insight ranges from completely unaware (agnosia), to extremely insightful (which contributes to frustration and anxiety)
• Disinhibited behaviour
• Insomnia or disturbances in sleep/wake patterns
• Increased susceptibility to physical stressors such as illness or bereavement that worsen intellectual deficits and other problems
• Tremor and/or myoclonic jerks or generalised seizures

Diet and Lifestyle:
• Countries in which saturated fat, sugar and calorie intake are lower, such as China and Nigeria, tend to have a lower incidence of AD (Hendrie et al. 2001; Ott and Owens 1998).
• Higher intake of fish is associated with a lower risk of dementia, possibly due to the high level of omega-3 fatty acids (Ott and Owens 1998).
• Higher intake of linoleic acid (omega-6 fatty acids ) found in margarine, butter, and other dairy products, is associated with an increased risk of cognitive impairment (Ott and Owens 1998). Decreasing omega-6 intake will help restore a better balance of omega-6 to omega-3 fatty acids.
• Evidence suggests that free radicals may be involve d in the development of AD; antioxidants may therefore play a role in its prevention (Christen 2000; Morris et al. 1998), and epidemiological studies suggest that dietary intake of vitamins A, E, and C decrease the risk for AD (Pitchumoni and Doraiswamy 1998). It may be reasonable to recommend foods rich in carotenoids and antioxidants, such as darkly colour ed fruits and vegetables.
• Foods which support healthy peripheral circulation, such as ginger, garlic, cinnamon and chilli are likely to be beneficial. Inflammation is a driver of AD and foods which reduce inflammation such as fish oil, ginger and many other spices are recommended.
• Regular exercise is beneficial, with the assistance of a carer if required.
• Presence of a pet dog—studies show that this increased appropriate social behaviours.
• Relaxation training and other exercises requiring focused attention (e.g., matching objects),
coupled with reward of refreshments, may improve so cial interaction and the ability to perform the requested attention-dependent tasks in the short term.