Prevention of this group of disorders has by far yielded the greatest success. The demonstration in 1911 by Noguchi and Moore of the brain infection by Treponema pallidum as the cause of general paresis'3,) opened the way in 1917 to its treatment by malaria therapy, and later to its prevention with penicillin; this is now a landmark in the history of medicine. The discovery of the aetiology of pellagra also led to its prevention and control, leading to the prevention of one type of dementia associated with alcoholism and avitaminosis.
These two once very frequent diseases have almost completely disappeared and there are many experienced psychiatrists who never come across a single case of either; with them also disappeared the history of their successful control. Although the same success has not yet been achieved in relation to vascular dementia, the control of hypertension and atherosclerosis (e.g. through the reduction of salt and fat intake) can significantly reduce brain damage and ensuing dementia (vascular or multi-infarct dementia).
In some developing countries, meningitis and malaria (and, to a lesser extent, inadequately treated epilepsy) are important causes of permanent brain damage which can also lead to dementing disorders. The environmental control of malaria and other brain infections, of which bacterial meningitis is the most important, and their early and prompt treatment can reduce the impact of the infection on the brain and prevent these forms of dementia (or mental retardation, depending on the age of onset).
More recently, it has been demonstrated that in some people infected with HIV, the initial manifestations of AIDS are acompanied by some forms of mental disorder, such as mood disorders or dementia.(4) The prevention of these forms of mental disorder follows the same measures as for the prevention of AIDS in general. However, it is not yet certain if the newer combined treatments (bi- and tri-therapy) can alter the course of AIDS when brain damage due to HIV has been confirmed.
As for mental retardation, up to 15 per cent of cases could be prevented by dealing with the causes that lead to it. A recent WHO publication (2) has set detailed guidelines for the prevention of some forms of this condition, namely, Down syndrome, fetal alcohol syndrome, phenylketonuria, and iodine deficiency syndrome. These preventive actions are both efficient and affordable even in very poor regions of the world.
The primary prevention of Down syndrome can be successfully achieved through the control of the age at which women become pregnant: ideally, the age range during which the risk is minimal is between 16 and 35 years, after which the risk increases almost exponentially, as shown in Fig 1. Amniocentesis is a procedure that can be very useful for the in utero diagnosis of Down syndrome (as well as of other problems and malformations). Wherever it is culturally, morally, and legally acceptable and permitted, a therapeutic abortion can be seen as another primary prevention measure.
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Fig. 1 Estimated risk of Down syndrome by related age. (Data from Gottesman.(5))
Appropriate nutrition, in addition to its major role in health promotion, can prevent at least two other forms of mental retardation, iodine deficiency and phenylketonuria.
The world population at risk of mental retardation due to iodine deficiency is approximately 1 billion and it still occurs in large numbers in some regions of the globe. (6) However, it can be very efficiently and cheaply prevented through the addition of iodine to salt, milk, flour, or water, or, in special situations, through injections of an oily solution containing iodine.(7)
Mental retardation due to phenylketonuria can also be successfully prevented through the early identification of children at risk who then receive a phenylalanine-free diet throughout their lives.(8)
Mental retardation and malformations seen in the fetal alcohol syndrome can be prevented if women stay away from alcohol during pregnancy, more particularly during the first trimester, or at least keep their alcohol intake below the dangerous limit of 15 g of ethanol per day. (9)
Ta.bie._l, summarizes actions which can effectively prevent some forms of mental retardation. Prevention of mental retardation is discussed further in Chapter.10.3.
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Table 1 Action to prevent mental retardation
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