Some causes of cognitive decline are treatable or even reversible while others, such as Alzheimer’s disease, are progressive and irreversible. Once brain cells are damaged and lost, no matter what the cause, they cannot be repaired.

How Dementia Affects Cognition

Dementia is a syndrome, a collection or grouping of symptoms that can affect, damage, or destroy cells in the brain. Dementia is progressive, meaning it gets worse over time. Dementia can be the main cause of brain disease or it can develop as a result of accidents, tumors and cysts, concussions, cardiovascular disorders, uncontrolled diabetes, neurologic disorders such as Parkinson’s disease, alcohol and drug abuse, and a number of other disorders and diseases.

Dementia affects cognition: thinking, memory, judgment, learning, language comprehension, attitudes, beliefs, safety awareness, morals, and the ability to plan for the future are all affected to some degree. Dementia also affects motor and sensory functions such as balance, spatial awareness, vision, pain processing, and the ability to modulate (control) sensory input.

Potentially Treatable Conditions

There are many conditions that can affect cognition, causing dementia-like symptoms; some of these conditions are reversible with appropriate treatment (NINDS, 2013):

• Reactions to medications or interactions between medications
• Metabolic and endocrine abnormalities
• Nutritional deficiencies
• Infections
• Constipation
• Head injuries and subdural hematomas
• Poisoning from exposure to lead, heavy metals, or other poisonous substances
• Alcohol, prescription medications, and recreational drugs
• Brain tumors, space-occupying lesions, and hydrocephalus
• Hypoxia or anoxia (not enough oxygen)
• Autoimmune cognitive syndromes
• Epilepsy
• Sleep apnea (NINDS, 2013)

Delirium and depression can also affect cognition, are particularly prevalent, and often overlooked or misunderstood in older adults. Both conditions can be superimposed on dementia, particularly in older hospitalized patients.

Delirium

Delirium is a syndrome with an acute onset and a fluctuating course. It develops over hours or days and is temporary and reversible. The most common causes of delirium are related to medication side effects, hypo or hyperglycemia (too much or too little blood sugar), fecal impactions, urinary retention, electrolyte disorders and dehydration, infection, stress, metabolic changes, an unfamiliar environment, injury, or severe pain.

Inattention is the most frequent clinical finding in a delirium episode. Other symptoms include difficulty with:

1. Orientation
2. Memory
3. Language and thought
4. Visuospatial abilities
5. Deficits in visual perception such as illusions and hallucinations (Cerejeira and Mukaetova-Ladinska, 2011)

The prevalence of delirium increases with age, and nearly 50% of patients over the age of 70 experience episodes of delirium during hospitalization. Delirium is under-diagnosed in almost two-thirds of cases or is misdiagnosed as depression or dementia. Early diagnosis of delirium can lead to rapid improvement. However, diagnosis is often delayed, and problems remain with recognition and documentation of delirium by healthcare providers (Hope et al., 2014).

Depression

Depression is a disorder of mood involving a disturbance of emotions or feelings. The diagnosis of depression depends on the presence of two cardinal symptoms: (1) persistent and pervasive low mood, and (2) loss of interest or pleasure in usual activities. Depressive symptoms are clinically significant when they interfere with normal activities and persist for at least two weeks, in which case a diagnosis of a depressive illness or disorder may be made (Diamond, 2015).

Along with apathy, depression is one of the most common mood disorders in Alzheimer’s disease (Nowrangi et al., 2015). Almost one-third of long-term care residents have depressive symptoms, while an estimated 10% meet criteria for a diagnosis of major depressive disorder. In the long-term care population, depression is both common and under-treated (Jordan et al., 2014).

Depression, although frequently present in those with Alzheimer’s disease, is much more persistent in dementia with Lewy bodies. Depressive symptoms in Alzheimer’s disease and dementia with Lewy bodies are associated with a greater cognitive decline and, in Alzheimer’s disease, significantly relate to lower survival rates over a three-year period (Vermeiren et al., 2015).

Early Detection and Referral

The majority of people with dementia currently do not receive a formal diagnosis. Only 20% to 50% of dementia cases in high income countries are recognized and documented in primary care, and this “treatment gap” is even greater in low and middle income countries. Early diagnosis of dementia is crucial since some treatments are more effective in the early stages, and earlier diagnosis and timely intervention provide health, financial, and social benefits (Ciblis et al., 2016).

Ultimately, the most successful model of treatment for Alzheimer’s disease will likely include early detection and control of physical factors (diabetes, hypertension, hyperlipidemia), followed by application of multifaceted, disease-modifying interventions to prevent the early and continued loss of neurons and to reduce the toxins that result in further cell deterioration (DeFina et al., 2013).