Down’s Syndrome (or Down Syndrome) is a genetic condition associated with a degree of learning disability, along with particular physical characteristics. The condition affects approximately ~1 in every 1000 babies born today1.
Down’s Syndrome is the most commonly occurring chromosomal disorder and is the leading cause of mild-moderate intellectual disability worldwide1, 2. It affects men and women of all economic, cultural, and geographical backgrounds.
In addition to intellectual impairment, Down’s Syndrome is associated with increased risk of medical problems including congenital heart defects, reflux, hearing loss, obstructive sleep apnoea, visual impairment, thyroid disease, and dementia3.
Pathology and functional impact of Down’s syndrome
Down’s Syndrome can affect multiple organ systems. All people with Down’s Syndrome have some degree of intellectual disability, which is due to changes in gene expression in brain tissue.
Various abnormalities of brain structure and function have been found, including abnormalities of neurones and their synaptic connections in the cortex and hippocampus4, regions heavily involved in cognition.
The cerebellum, involved in motor co-ordination and some aspects of cognition, has also been commonly implicated. Current models of Down’s Syndrome emphasise that it is ‘late-developing’ brain structures that are most affected, and that these regions do not show the expected development over time in people with the condition5.
The majority of individuals with Down’s Syndrome have intelligence quotient (IQ) scores less than 70, consistent with generalised or ‘global’ cognitive problems; however, individuals also show more specific impairments in memory and cognitive flexibility5.
These findings highlight the importance of using sensitive neuropsychological assessment tools capable of fractionating specific cognitive domains.
Research and development in Down’s syndrome
There is no standard treatment for Down’s Syndrome: individuals with the condition vary widely in how they are affected both intellectually and in terms of physical health, and healthcare needs can change considerably over time.
Current evidence-based treatments seek to maximise quality of life and everyday functioning, rather than being capable of reversing the genetic basis of the condition.
Children and adults with Down’s Syndrome should have access to multi-disciplinary support, which can involve input from doctors, educational experts, speech and occupational therapists, and social workers6. Examples of medical interventions that may be needed include surgery to correct congenital heart defects or a special diet to minimise digestive problems7.
Cognitive deficits in Down’s Syndrome represent a key target for novel treatments, in order to maximise everyday functioning and quality of life. This is relevant in view of the intellectual disability occurring generally with the condition, but also due to the association between Down’s Syndrome and elevated risk of Alzheimer’s Disease as individuals get older.
In reviewing the neurobiology of the condition, it has been suggested that interventions targeting neurochemical systems such as the glutamatergic, cholinergic, and norepinephrine should be investigated further7.
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Haydar T.F., and Reeves R.H., (2012). Trisomy 21 and early brain development. Trends Neurosci.
Edgin J.O. (2013). Cognition in Down syndrome: a developmental cognitive neuroscience perspective. Wiley Interdiscip Rev Cogn Sci.
Das D., et al (2014). Neurotransmitter-based strategies for the treatment of cognitive dysfunction in Down syndrome. Prog Neuropsychopharmacol Biol Psychiatry.
Deutsch S.I., et al (2014). Targeting the α7 nicotinic acetylcholine receptor to prevent progressive dementia and improve cognition in adults with Down's syndrome. Prog Neuropsychopharmacol Biol Psychiatry.
- Genes and human disease. World Health Organization, 2015.
- Global Down Syndrome Foundation, 2015.
- Centers for Disease Control and Prevention, USA. Data and statistics, Down Syndrome, 2014.
- Haydar TF, Reeves RH. Trisomy 21 and early brain development. Trends Neurosci. 2012 Feb;35(2):81-91.
- Edgin JO. Cognition in Down syndrome: a developmental cognitive neuroscience perspective. Wiley Interdiscip Rev Cogn Sci. 2013 May;4(3):307-17.
- NIH Eunice Kennedy Shriver National Institute of Child Health and Human Development. What are common treatments for Down Syndrome? 2015.
- Das D, Phillips C, Hsieh W, Sumanth K, Dang V, Salehi A. Neurotransmitter-based strategies for the treatment of cognitive dysfunction in Down syndrome. Prog Neuropsychopharmacol Biol Psychiatry. 2014 Oct 3;54:140-8.