Objective: To determine diagnostic criteria used to identify delirium in Parkinson’s disease (PD) and its prevalence via a systematic literature review.

Background: People with PD may be at increased risk of delirium and subsequent adverse outcomes, such as cognitive decline and increased mortality. Delirium is an acute neuropsychiatric syndrome that is common in older adults. It has overlapping symptoms with Parkinson’s and dementia, making it difficult to identify. Therefore, it is important to determine how delirium has been defined or diagnosed in PD patients previously and to better understand its prevalence.

Methods: Seven databases were used identify all articles published before February 2017 comprising two key terms: “Parkinson’s Disease” and “delirium”. Data were extracted from studies meeting predefined inclusion criteria.

Results: Twenty articles met the inclusion criteria and had full text available. Delirium was identified/diagnosed using seven different sets of criteria. Only three studies used validated diagnostic criteria; a further four used a validated delirium assessment tool for non-specialists. Other studies used a broader definition, which included symptoms or presence of hallucinations. In six studies, no methods were stated. Delirium prevalence in PD ranged from 0.3-60% depending on setting and diagnostic criteria. Higher rates of delirium were reported among medical in-patients and patients undergoing surgery (11-60%). The prevalence of delirium in patients undergoing deep brain stimulation (11-27%) was lower compared to other non-DBS surgical procedures (22-60%). Four studies reported that PD was associated with an increased risk of developing delirium.

Conclusions: The prevalence of delirium in PD varies widely between studies and clinical settings, ranging from 0.3% to 60% of subjects, as do the criteria used to identify or diagnose delirium. Broader definitions based on delirium symptoms have the potential to misidentify delirium as these symptoms are common in PD. A number of studies excluded patients with PDD; as people with dementia may be at increased risk of delirium, a key group of people are likely to have been under-represented. Further prospective research is needed to accurately determine the prevalence of delirium in Parkinson’s, management strategies and outcomes, and to evaluate diagnostic criteria to differentiate between the overlapping symptoms of Parkinson’s and delirium.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/identifying-delirium-and-it-prevalence-in-idiopathic-parkinsons-disease/