Introduction

Mild Cognitive Impairment (MCI) is characterised by a noticeable decline in cognitive function that is greater than expected for one’s age but is not so severe that it significantly impacts daily life.¹ In simple terms, it is a transitional stage of cognitive decline that is worse than what is expected from normal ageing but it's also distinct from dementia. MCI is not as severe as cognitive disorders like dementia² however in some individuals it can be an early sign of dementia.

While normal ageing involves a certain level of cognitive decline such as deterioration in learning ability, verbal fluency and reaction time,³ MCI involves more significant cognitive decline, particularly overall executive function, which includes self-control, memory, and ability to think flexibly and adapt.⁴

Symptoms of mild cognitive impairment

Most people get more forgetful as they age, and struggle to focus and think the way they may have when they were younger. MCI patients may find their memory and mental function gradually worsen, but their ability to continue with their daily activities may make them believe that the changes are normal, and can be chalked up to getting older. 

If you’re unsure whether changes in your mental function are due to normal healthy ageing, or perhaps a more severe disease, here are a few symptoms to watch out for: 

• Mood changes:⁸ Depression and anxiety are common in MCI and are a consequence of the cognitive decline experienced
• Behavioural changes:⁸ Apathy and withdrawing from social activity
• Memory loss: you might find difficulty in remembering recent events
• Difficulty learning new things
• Reduced ability to pay attention: Struggling to focus for long periods of time 
• Language: Difficulties finding the right word, struggling to appropriately articulate and communicate thoughts
• Executive function: Difficulty planning and organising, struggling with problem-solving, multitasking etc. 

Clinical presentation of mild cognitive impairment

First defined in 2003, two major clinical subtypes of MCI exist: (i) Amnestic-MCI, and (ii) Non-amnestic MCI.⁵ In both subtypes, the decline may occur in single or multiple domains, giving us 4 distinctive types of MCI.⁸ 

• Amnestic-MCI (aMCI): Primarily characterised by significant memory impairment. Those with amnestic-MCI find it difficult to remember recent events and other occurrences.
  • Single domain aMCI involves impairment only in memory and recognition
  • Multiple domain aMCI, also known as mixed MCI, involves impairment in memory, recognition, language, visuospatial ability, and executive function. This is also associated with a higher risk of developing Alzheimer’s disease⁷
• Non-amnestic MCI: Characterised by significant impairment in other cognitive domains, with absence of memory impairment. This may include language, executive function, and visuospatial ability.⁶ This type is associated with progression to types of dementia other than Alzheimer’s⁷

Identifying MCI: Where to go from here?

Patient history and self-reporting

Unlike in more severe diseases like dementia, many MCI patients tend to be aware of the changes in their cognitive ability and have great insight into the symptoms they experience, particularly with memory loss. Similarly, close friends and family may also be able to provide insight into the patient’s cognitive changes: for example, the repeated questions, forgotten conversations and the reduced abilities to manage daily tasks. 

Aspects of daily life and executive functioning are insights that can only be provided by the patient and those around them and have been shown to be reliable even in older adults with cognitive impairment.¹⁴ All these observations tend to prompt a visit to a physician and have been proven to be valuable in the diagnosis of MCI.¹³ In the UK, individuals can be referred by their general practitioner to memory clinics, where either a psychiatrist or specialist memory service nurse can provide a thorough assessment of any memor 

Cognitive assessments

There are a number of standardised tests that are used by clinical practitioners to assess the cognitive levels of concerned individuals.¹⁵ This includes the mini-mental state examination (MMSE) and Montreal cognitive assessment (MoCA), which tests the function of multiple cognitive domains, including attention, short-term and working memory, visuospatial abilities, executive function, language, and orientation, and it can give an overall assessment of an individual's cognitive function

Biomarkers and imaging

2 main sets of biomarkers are a build-up of the protein beta-amyloid, and neuronal injury which both are linked to Alzheimer’s disease. Not only do these markers help identify MCI but they also help differentiate from Alzheimer’s disease. 

Imaging methods like PET (positron emission tomography) imaging⁹ and MRI (magnetic resonance imaging)¹⁰ provide clear images of what is going on inside the brain. These imaging methods help reveal any changes in the structure and function of the brain that are commonly associated with MCI, including degeneration of brain tissue in regions related to cognitive function (known as atrophy)¹¹ and abnormal buildup of amyloid protein known as amyloid plaques in the brain.¹² 

It is important to note that although changes in cognitive function may be due to MCI, this is not always the case; other health conditions can cause memory problems such as sleep disorders, side effects of medications, and infections, particularly in the elderly. Therefore your health practitioner will take a detailed history, and examination and order additional investigations such as blood tests and imaging to rule out other causes. 

Epidemiology and risk factors

While there has been a lack of homogeneity in the reported prevalence of MCI,¹⁷ the current global prevalence of the disease has been found to be approximately 19.7%,¹⁸ appears to be higher in those aged 70 and over.²¹

Common risk factors^{16, 17}

• Genetic factors: Certain genetic factors such as having the  APOE-ε4 allele are high risk factors for developing MCI as well as progression to Alzheimer’s disease.
• Old age: Prevalence of MCI is higher at ages above 50, and evidence suggests that the risk of developing MCI increases with age¹⁹
• History of traumatic brain injury, diabetes, and hypertension²⁰
• Poor lifestyle habits: Smoking, poor diet, lack of consistent physical activity,  and excessive alcohol consumption have all been linked with MCI

Conclusion

Mild Cognitive Impairment (MCI) is not just your average ageing process - it’s a transitional stage of cognitive decline that may cause more serious problems further down the line. Recognising symptoms such as memory loss, difficulty staying focused or learning, as well as mood changes, may help to differentiate MCI from normal ageing, and allow for timely intervention to prevent progressing to more severe conditions like dementia. Understanding and addressing MCI will enable individuals to maintain their mental capabilities and improve their overall quality of life. 

FAQs

Q: Can MCI be reversed? 

A: In some cases, it is possible for MCI to be reversed back to the normal ageing process, especially if it is caused by modifiable factors such as medication, sleep disorders, depression, or other mental illnesses. It is important to note that this is not the case for all MCIs, and ongoing monitoring is important. 

Q: Does MCI always progress to dementia? 

A: MCI does not always progress to dementia; while it can increase the risks of developing dementia in some individuals, many are able to remain stable with regular monitoring and timely management. With the correct management, it is completely possible to slow the progression of the disease. 

Q: Are there any lifestyle changes that can be made to manage MCI? 

A: Engaging in regular physical exercise, maintaining a healthy balanced diet, remaining mentally active, and maintaining social activities and connections can contribute to maintaining healthy cognitive function.