Cognitive Impairment

Cognitive impairment is the decline in the brain’s functional abilities (memory, communication, perception and reasoning) when compared with individuals of the same age. The reduction in mental capacities interferes with the performance of daily activities, which is why both the patient and those around them are often able to identify it.

Although cognitive impairment is more common in older adults, it is important to distinguish between natural ageing, in which the ability to learn and remember slows down, and the loss of mental abilities. When symptoms interfere with a person's independence, it is considered a pathological process requiring medical evaluation.

There are different stages of cognitive impairment depending on the impact of symptoms on a person's independence:

• Mild Cognitive Impairment (MCI): the decline in abilities is greater than expected for age, but the patient maintains independence.
• Moderate Cognitive Impairment or Mild Dementia: there is partial dependence because limitations are evident.
• Severe Cognitive Impairment or Severe Dementia: dependence is total due to profound loss of brain functions.

The prognosis of cognitive impairment varies according to age and degree of involvement. It is estimated that between 10% and 20% of patients with mild cognitive impairment develop dementia within one year.

Symptoms

The symptoms of cognitive impairment are similar at any age, although their intensity may vary. Initially, they are usually subtle and may be mistaken for normal age-related forgetfulness, but attention should be paid if they occur persistently or gradually worsen. The most characteristic symptoms are:

• Loss of recent memory: forgetting conversations, important events or appointments.
• Difficulty performing daily tasks, such as dressing or cooking, following instructions or completing tasks.
• Disorientation in time and space: getting lost in familiar places, difficulty estimating distances or not knowing the date.
• Problems with verbal expression: being unable to find the right words or follow a conversation.
• Difficulty following a train of thought: having trouble following the plot of a film or book.
• Poor judgment: difficulty making decisions or engaging in abstract reasoning.
• Altered appetite regulation: changes in the brain may modify hunger and satiety signals.
• Difficulty recognising people or understanding the purpose of objects.
• Changes in mood or personality: irritability or aggression, loss of interest in previously enjoyed activities, anxiety in situations previously handled normally, or depression.
• Misplacing objects: placing items in unusual locations and forgetting how they got there.

Causes

Cognitive impairment occurs as a result of damage to or destruction of nerve cells in the brain. This neuronal damage may be caused by a wide variety of factors, including:

• Neurodegenerative diseases: disorders that cause progressive loss of nerve cells in the central nervous system.
  • Alzheimer's disease: the most common cause of dementia. It progressively destroys memory, thinking abilities and the capacity to carry out daily activities.
  • Lewy body dementia: the accumulation of excess alpha-synuclein protein (which facilitates neuronal communication) in the brain leads to loss of mental functions.
• Vascular cognitive impairment: the second most common cause of dementia, referred to as vascular dementia in these cases. It results from damage to brain tissue caused by interruption of blood flow to the brain during conditions such as stroke or multiple small infarctions.
• Infectious diseases: infections may accelerate neurodegenerative processes through systemic inflammation, vascular damage or invasion of the central nervous system.
• Traumatic brain injuries: depending on the affected brain region and injury severity, they may lead to loss of mental abilities and executive functions.
• Brain tumour: if cancer cells affect neuronal circuits, memory, attention and language control may be impaired, executive functions may become more difficult, and behavioural or personality changes may occur.
• Vitamin deficiencies: deficiencies of B-complex vitamins, particularly vitamin B12 and vitamin B1, may manifest as confusion, mental slowing and memory loss. This form of cognitive impairment is reversible if treated promptly.
• Metabolic disorders: brain function may be affected when the body carries out chemical processes abnormally. As with vitamin deficiencies, this condition is reversible if detected and treated early.
  • Diabetes and insulin resistance: hyperglycaemia and hyperinsulinaemia may damage brain tissue.
  • Metabolic syndrome: obesity, hypertension and dyslipidaemia cause inflammation and vascular damage in the brain.
  • Hypothyroidism: negatively affects memory and cognitive performance.
  • Severe electrolyte or glucose imbalances, as well as liver or kidney failure, may result in metabolic encephalopathy.

Risk Factors

The main risk factors for cognitive impairment are:

• Advanced age: the likelihood increases after the age of 65.
• Genetic predisposition: the APOE ε4 gene increases the likelihood of developing dementia and Alzheimer's disease.
• Family history.
• Hypertension.
• Hypercholesterolaemia, particularly elevated levels of low-density lipoprotein (LDL).
• Diabetes.
• Smoking.
• Obesity.
• Sedentary lifestyle.
• Depression.
• Untreated hearing or vision loss, as the brain must exert additional effort, accelerating neuronal wear and reducing mental and social stimulation.
• Limited intellectual activity.
• Low educational level.

Complications

The progression of cognitive impairment from a mild condition to severe dementia leads to various complications that affect the patient's quality of life and that of their surroundings:

• Loss of autonomy: progressive inability to perform basic activities of daily living, such as personal hygiene or eating.
• Safety risks: the likelihood of domestic accidents, falls or disorientation increases considerably.
• Communication problems: difficulty expressing oneself and understanding others.
• Social isolation: resulting from the inability to communicate normally.
• Behavioural disorders: agitation, aggression, apathy or depression may occur, depending on the patient.
• Reduced life expectancy: in advanced stages, total dependence and frailty increase the risk of diseases that may ultimately be the cause of death:
  • Pneumonia: increased difficulty swallowing facilitates the passage of food, liquids or saliva into the airways. Additionally, reduced strength and coordination make coughing to clear mucus more difficult.
  • Malnutrition: alterations in appetite regulation, physical limitations, behavioural disorders and difficulties recognising everyday objects may lead to inadequate food intake.
  • Infections: deficiencies in personal care, swallowing disorders, possible dehydration or malnutrition, the use of incontinence pads and reduced immune response favour the development of infections.

Which specialist treats cognitive impairment?

The diagnosis and treatment of cognitive impairment are carried out within the specialty of Neurology. For optimal management of the condition, specialists in Geriatrics, Physical medicine and Rehabilitation, Neuropsychology and Psychiatry are also involved.