In the literature there are several epidemiological studies that highlight an increased risk of Alzheimer's Disease (AD) in elderly subjects with Down syndrome (DS), while there are few data regarding the incidence of dementia in people with Intellectual Developmental Disorders (PwIDD) of other etiology. This lack of knowledge also affects the comparison with the general population. Some authors have reported comparable incidences while others argue for significantly higher numbers. This discrepancy may depend on the criteria used in different studies for the selection of samples: diagnostic procedures and background characteristics, in particular age and level of intellectual disability, can vary considerably. Numerous data from the research seem to indicate specific risk factors for PwIDD and an increased vulnerability to the development of neurodegenerative diseases. In a recent study, Dr. Strydom and his colleagues at University College London have estimated the incidence rate of dementia in a sample of 222 people with IDD without DS and of at least 60 years of age. The incidence was very high, up to 5 times greater than that of the general population. The age group most affected was that between 70 and 74, significantly lower than the general population. There were no significant differences in the two sexes, which deviates from the general population where the incidence is higher in women instead. These results seem to confirm that older adults with IDD without DS represent a group at high risk for developing dementia. The tripling of genes on chromosome 21, which also includes the gene for the amyloid precursor protein, would not represent the only cause of vulnerability to AD for IDD. Other recent research has identified cognitive impairment associated with mutations in the course of Kleefstra syndrome or syndrome 'X fragile. The identification of the etiological factors and risk factors for dementia in PwIDD represents a field of extreme interest, which could also be helpful for understanding the origin and development of the disease in the general population. One of the main difficulties in the advancement of knowledge about dementia in the IDD is in the early detection of signs and symptoms. The organization of neuro-psychiatric services does not include a screening program which would allow prompt arrangement of the most appropriate therapeutic interventions and rehabilitation, in addition to providing useful data for research.
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