The word dementia derives from the Latin prefix “de-,” meaning “out of,” plus “mentis,” meaning “mind,” hence “out of one's mind”—an apt description for the condition.
The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) identifies dementia as a major neurocognitive disorder (see Table 1 for diagnostic criteria) characterized by a significant cognitive decline from a previous level of performance in one or more of six cognitive domains, with substantially impaired cognitive performance preferably documented by standard neuropsychological testing or by another dementia assessment tool. The six domains are listed in Table 2. The cognitive deficits interfere with independent daily activities, do not occur exclusively in the context of delirium, and cannot be better explained by another mental disorder (e.g., major depressive disorder, schizophrenia).
Whereas many major neurocognitive disorders may occur in younger people, the term dementia is customarily applied only to older adults. Dementia is a general, nonspecific term that encompasses several underlying major neurocognitive disorders. Behavioral disturbances, including psychotic symptoms, mood disturbance, agitation, apathy, aggression, combativeness, and “wandering off” (2018 International Classification of Diseases, 10th Revision, Clinical Modification [ICD-10-CM] code Z91.83) may also be present.
In the vast majority of cases, dementia is due to one of five conditions: Alzheimer disease (60% to 80% of cases), Lewy body dementia, frontotemporal dementia, vascular (multi-infarct) dementia, and Parkinson disease. Memory and language dysfunction are almost always present. Alternative causes of major neurocognitive disorders that primarily affect younger people include traumatic brain injury, HIV infection, prion disease, substance use, and Huntington disease.
The correct coding of dementia can be complex and confusing, but clear and precise medical record documentation is essential for accurate classification of severity of illness, quality of care measurement, and reimbursement. The underlying cause of dementia should always be identified whenever possible.
In all cases, the presence or absence of behavioral disturbance should be documented. In almost all circumstances, dementia with a behavioral disturbance contributes to the severity of illness in contrast to no behavioral disturbance. Unspecified dementia (which includes senile or presenile dementia) without behavioral disturbance is assigned code F03.90; with behavioral disturbance, it is coded as F03.91. Similarly, vascular dementia has two separate codes: F01.50 (without) and F01.51 (with).
The other forms of dementia common in older adults require two codes: one code (sequenced first) for the underlying condition and a separate code (sequenced second) specifying if it is with or without a behavioral disorder. No separate code is assigned for “dementia” in these conditions since it is intrinsic to the diagnosis. Table 3 lists codes for these four underlying conditions. The additional codes related to behavioral disorder are F02.80 (without) and F02.81 (with).
Alzheimer disease (code G30.9) has unique codes to further specify it as early onset (G30.0) or late onset (G30.1). ICD-10-CM also classifies Parkinson disease with dementia as Lewy body dementia (code G31.83).
Patients with dementia are susceptible to episodes of delirium with any physiological, psychological, or circumstantial stress, as during a hospital admission. Delirium superimposed on dementia and “sundowning” are included under code F05 (delirium due to a known physiological condition), which contributes significantly to severity of illness classification.
In summary, dementia is classified by DSM-5 as a major neurocognitive disorder and is customarily applied only to older adults. Dementia is characterized by significant cognitive decline in one or more of six cognitive domains (preferably documented by standard neuropsychological testing or by another dementia assessment tool) that interferes with independent daily activities. In older adults, dementia is typically caused by one of five underlying conditions: Alzheimer disease, Lewy body dementia, frontotemporal dementia, vascular (multi-infarct) dementia, and Parkinson disease.
Precise documentation that allows correct code assignment is essential to fully describe the patient's condition and severity of illness. The underlying cause should always be documented when known. Behavioral disturbances such as psychotic symptoms, mood disturbance, agitation, apathy, aggression, combativeness, and “wandering off” should be identified and documented as a behavioral disturbance. Delirium superimposed on dementia and “sundowning” should also be documented whenever they occur.