Mild Cognitive Impairment (MCI) is considered an intermediate state between normal ageing and dementia. Around 3-19% of adults aged 65 and above develop MCI and the risk of progression towards dementia is 10-20% a year. As pharmacological therapies have not proven their benefits in patients with MCI, clinicians should opt for non-pharmacological interventions. This article aims to describe different non-pharmacological, supportive therapies with evidence of positive effect against the progression of cognitive decline. 

The normal process of ageing is associated with progressive cognitive decline due to age. Two mechanisms have been proposed for the associated functional loss: reduced brain activity and decline in brain function.¹

Even though some degree of cognitive deficits is considered to be in the normal range for age, level of education and social function, 3-19% of adults aged 65 or more develop MCI.²

There are few guidelines and recommendations to support the diagnosis of MCI, while for clinicians it is of great importance to recognise MCI, understand the possible evolution towards dementia (10-20% per year)³ and manage the progression of cognitive impairment.⁴

Definition of MCI

Considered an intermediate state between normal ageing and dementia,⁵ MCI is a clinical syndrome which identifies patients with symptomatic cognitive impairment who are not demented. This means that the cognitive changes are mild and there is no evidence of significant impairment in social or occupational functioning.⁶

It is important to differentiate between MCI and any other possible cause of cognitive impairment such as vascular, traumatic or other medical conditions.

MCI diagnosis and risk factors

For the diagnosis of MCI two sets of criteria have been established:⁶

Clinical criteria 

• Change in cognition observed by the patient or informant 
• Objective cognitive impairment 
• Activities of daily living and independence are not affected.

Research criteria

• Markers of Aβ protein deposition (CSF – Aβ protein/PET amyloid imaging)
• Markers of neural injury (CSF tau/phosphorylated tau; hippocampal volume or medial temporal atrophy; SPECT perfusion imaging)
• Associated biochemical change (cytokines, oxidative stress).

If the diagnostic criteria are met, it is necessary to determine the type of MCI and to rule out plausible primary causes for the cognitive impairment.⁴ If a treatable physical disorder is diagnosed which may be contributing to the decline in cognitive function, this should be managed and a reassessment of function undertaken. 

MCI can be subdivided into two categories: amnestic MCI (aMCI) and non-amnestic MCI. Even though MCI can turn into any type of dementia (vascular, Lewy body, Alzheimer dementia), recent findings suggest that patients diagnosed with MCI develop Alzheimer dementia (AD) more frequently.^5,7 From a clinical perspective, aMCI is considered to be a mild cognitive impairment due to AD.⁶ Recent findings suggest that aMCI and AD share primary neurodegenerative aetiology. 

In aMCI, neurofibrillary pathology can be found in the temporal lobe, while AD pathology implies the presence of neurofibrillary tangles in the temporal lobe and neo-cortex.⁸

Due to the risk of progression towards AD, the assessment and prevention of risk factors for developing aMCI is very important. The level of education attained is known to be a protective factor for cognitive impairment. 

According to Wilson RS et al,⁹ education is only associated with a higher baseline cognitive level and it does not influence the rate of cognitive decline. Other putative protective factors are: maintaining a healthy diet; minimising cardiovascular risk factors (eg. midlife obesity, smoking, alcohol abuse, lipid levels); and moderate physical activity.^10,11 Neuropsychiatric pathology is considered to be a risk factor for MCI and AD. In a Canadian cross-sectional nationwide study¹² apathy and depression were high predictors of mild and severe cognitive impairment.

Supportive therapies

Risk factors for cognitive impairment should be managed for all individuals, not only for those patients suffering from aMCI. In the case of already-diagnosed patients, the aim is to provide therapies to maintain cognitive performance and delay the onset of AD. Pharmacological therapies like cholinesterase inhibitors; antioxidants, cyclo-oxygenase-2-selective inhibitors proved of little benefit in preventing cognitive decline for persons with aMCI.⁴ This leaves the practitioner with the option of non-pharmacological therapies. Due to the heterogeneity of the risk factors, individualised supportive therapies may be required. 

The first steps in defending against the progression of cognitive decline are to encourage a healthy lifestyle and cognitive leisure activities.^10,13

Diet

Fatty acids are a common factor in dietary recommendations for people with cognitive decline. There are three types of dietary fatty acids: saturated fatty acids (SFAs); monounsaturated fatty acids (MUFAs); and polyunsaturated fatty acids (PUFAs). Comparing these three types, high dietary levels of SFAs appear to have a negative effect on global cognition and verbal memory,¹⁴ while MUFAs and PUFAs are associated with a lower risk of cognitive decline.¹⁵

It is hypothesised that the underlying mechanisms are a decrease in inflammation due to antioxidant effect and the protection of the neuronal membrane from amyloid accumulation and atherosclerosis. The most important PUFA fatty acid is docosahexaenoic acid (DHA), an omega-3 fatty acid that can be found in the brain and heart. High dietary levels of DHA seem to be protective against the development of AD and coronary heart disease.¹⁶ Even though MUFAs and PUFAs have proven protective effects against cognitive decline, epidemiological evidence suggests that they are not efficacious in AD pathology.^15,16

Along with the consumption of MUFAs and PUFAs, there is some positive evidence regarding the protective role of light-to-moderate alcohol consumption. According to Lee et al, moderate alcohol use is associated with lower risk of dementia and pre-dementia syndromes in comparison to non-drinkers or frequent drinkers.^17,18 Dietary use of macronutrients like fruits or vegetables is recommended, but further evidence regarding their effects is still needed.¹⁷

The nutritional principles presented can be found in the Mediterranean diet. According to Solfrizzi et al, those adhering to this type of diet have a lower risk of cognitive decline and are not only protected from developing AD, but also from MCI.¹⁸

Physical leisure activity

Leisure activities have three different components: physical, social and mental.¹⁹ The term refers to those activities in which an individual takes part with pleasure, and which are not related to work. Along with aerobic fitness, physical leisure activities such as tennis or swimming seem to challenge not only physical resistance but also cognitive function, thus having a beneficial effect on mind and body. 

Adopting a healthy lifestyle means not only improving dietary habits, but also ensuring regular physical activity. As presented earlier, dietary fatty acids, along with fruits and vegetables and low alcohol consumption, are most likely to have a protective role against cognitive decline in MCI. Along with dietary intervention, sports activities appear to play an important role in the process of neuronal protection.²⁰

The first beneficial outcome of regular physical training is the prevention of cardiovascular risk factors (obesity, lipid levels, insulin resistance and blood pressure) which are also considered to be risk factors for neurodegenerative disorders.²¹ Secondly, regular sports activities improve brain plasticity leading to memory and learning enhancement. 

A proposed mechanism for this action, derived from animal models, is an increase secretion of brain-derived neurotrophic factor (BDNF). BDNF enhances neuronal development and synaptic function.²⁰

In addition, memory and learning improvement appear to be related to hippocampal volume. The hippocampus is a region of the brain that suffers a shrinking process with age, even in normal adults;^22,23 this process is accelerated by MCI or dementia pathology. In elderly individuals with an active lifestyle, the hippocampus has a larger volume and the brain has a better blood flow. Another observation is that, in physically active individuals, the volume of white and grey matter in the prefrontal cortex is larger.^20,22

Aerobic activities in particular appear to support positive cognitive function. Besides the prevention of cognitive decline, sports activities seem to have a better effect on memory for people with MCI in comparison to non-cognitively impaired individuals.²⁴ Randomised control trials suggest that individuals with MCI or AD score higher in cognitive tests following six to 12 months of regular physical activity. Even though sports activities are encouraged at every age, midlife physical exercise seems to be most protective against cognitive decline.²⁰

Cognitive leisure activities

The mental component of leisure activities refers to a wide range of cognitive tasks such as reading or solving puzzles.²⁵ Cognitive activity appears to be protective against the development of MCI and AD because of its beneficial outcome on brain reserve.²⁶ The brain reserve is the capacity of the brain to maintain cognitive function despite the process of ageing. Other factors that have an important influence on brain reserve are different lifestyle elements such as work complexity, education, intellectual challenges and complexity of social network.¹⁹ Mental leisure activities are considered to be intellectually challenging and consequently protective against cognitive decline. Even though there is little evidence in the literature regarding the effect of this type of mental activity in people already diagnosed with MCI, mid and late-life practice of cognitive leisure activities has proven useful as preventive therapy for MCI and AD.²⁶

Discussion

Supportive strategies presented in this article have greater success against cognitive decline when used in combination. For every individual diagnosed with aMCI, the optimum combination of diet, physical activity, and cognitive leisure activities must be found.¹⁰ When different supportive strategies are suggested, other health comorbidities (eg. cardiovascular, nutritional deficits etc.) must be taken into consideration. As pathological cognitive decline becomes more and more significant, other supportive strategies like cognitive training may be utilised. 

Cognitive training provides two types of intervention: compensatory training and cognitive stimulation therapy. Compensatory training teaches individuals with cognitive impairment different ways to accomplish tasks such as using notes or calendars.²⁸ Cognitive stimulation therapy aims to improve different cognitive domains through exercise (eg. memory and attention games) and enhance the quality of life for people with cognitive impairment.²⁹ When diagnosed in a timely manner there are a number of strategies which may be employed to support an individual with MCI. However, the importance of health education and minimising of risk factors remains paramount in the prevention and management of this disorder.

Declaration of interest: none.

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