LIGHT COGNITIVE DEFICIT: STEM PROGRESSION TOWARD DEMENTIA

Research Published February 11 2016
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In Nature Review Neurology, Professor Harald Hampel and Doctor Simone Lista highlight the need to refine the diagnostic criteria for mild cognitive impairment (MCI) in order to set preventive measures and stem the progression toward dementia in people at risk.

People with mild cognitive impairment (MCI) have problems involving memory, language, reasoning or judgment that are more serious than those involved by normal aging. However, these alterations of cognitive abilities are usually not serious enough to interfere with daily life or personal autonomy. However, they can be an early sign of Alzheimer’s disease (these appear at prodromal stage, in other words at the harbinger phase of the disease) and often lead, however not necessarily, to dementia.

Dementia affects 47.5 million people worldwide and is one of the main causes of disability and dependence in the elderly. To date, there is no way to treat it effectively. But its physical, psychological, social and economic consequences turn out catastrophic for patients, care givers, families and society.

The new criteria proposed by an international consensus coordinated by Professor Bruno Dubois for diagnosing Alzheimer’s disease is a major step to assess the risk of progression from MCI toward dementia. These criteria are based on clinical observation associated to the research of biomarkers (morphological and metabolic changes in the brain, presence of specific proteins in the cerebrospinal fluid).

However, the specific diagnostic criteria for MCI must be refined and harmonised in order to establish a clinical-biological definition incorporating in the same way both biomarkers and clinical observations. This would also allow optimizing the diagnostic criteria for Alzheimer’s disease at early stages: preclinical asymptomatic stage (patients at risk of developing the disease) and prodromal stage. Harmonising these criteria would allow to better target future therapeutic trials that aim at slowing MCI progression toward dementia.

Indeed, the challenge is to prevent the development of Alzheimer’s disease and develop treatments to fight it before its damage gets irreversible. One crucial point is the development of methods for early identification in persons at risk. Indeed, the cellular and molecular mechanisms leading to dementia similar to that of Alzheimer set up decades before the development of clinical symptoms. This window gives researchers an opportunity to try and delay the development of the disease. Furthermore, the accurate estimation of MCI prevalence and the identification of patients likely to develop Alzheimer’s disease are very important at clinical level to reliably test treatments that could slow down the progression toward dementia.

Currently, while no curative solution exists, the only possible preventive measure to reduce the growing number of MCI and dementia is the management of risk factors (diabetes, cardiovascular risk, depression) as soon as possible, preferably at asymptomatic stages. Initiatives to promote and protect mental health throughout life also appear to have a positive impact.

References:
Hampel H, Lista S. Dementia: The rising global tide of cognitive impairment. Nat Rev Neurol. 2016 Jan 18. doi: 10.1038/nrneurol.2015.250.

Professor Harald Hampel holds the “Anticipating the Alzheimer’s Disease” AXA-UPMC Chair at the Sorbonne University. He is a member of Professor Bruno Dubois team at IM2A and ICM.