The relationship among frailty, delirium and attentional tests to detect delirium: a cohort study

Highlights

• This study supports the idea that frailty is a predisposing factor for delirium

• Frailty also affects the performance at attentional tests used to detect delirium

• The cut-point to detect delirium with attentional tests varies according to frailty

• Frailty may be assessed in hospitalized olders to assess their delirium risk

Abstract

Background

Few studies explored if frailty predisposes to delirium in hospitalized older patients. The aims of this study were to evaluate if frailty: 1) is independently associated with delirium, and 2) affects the patient's performance in three tests of attention used to detect delirium.

Methods

Data are from a prospective cohort study of patients admitted to an Acute Geriatric Unit (AGU). Frailty was operationalized using the health deficit accumulation model (38-item Frailty Index). Delirium was screened using the 4AT, and the diagnosis confirmed with the DSM-5th criteria. During the first 7 days from the hospital admission, patients also underwent a double-blind assessment of attention using three ad hoc tests (i.e., Months of the year backwards, MOTYB; Days of the week backwards, DOWB; and Count backwards from 20 to 1, CB).

Results

Eighty-nine patients were included (mean age 83.1 years, standard deviation 6.0). Forty-two (47.19%) patients were frail, and 37 (41.7%) had delirium. The likelihood of delirium was significantly higher in frail compared to the non-frail patients; it was also inversely associated with the three attention tests. Using the MOTYB test, the ability to discriminate delirium was similar in patients with (Area Under the Receiving Operator Characteristic [AUROC] 0.88, 95% Confidence Interval [CI] 0.82-0.92) and without frailty (AUROC 0.93, 95%CI 0.90-0.95) whilst was markedly different between the same groups using either DOWB and CB.

Conclusions

Frailty is associated with delirium in hospitalized older patients and can influence the patient's performances at attentional tests that are commonly used to screen delirium.

Introduction

Frailty and delirium are two medical conditions of older people that have been described as geriatric giants (1). Frailty is characterized by a decrease of functional reserves due to a multisystemic physiological dysregulation. It results in an increased level of vulnerability to endogenous and exogenous stressors (2), and in an increased risk of negative health-related events.

Delirium is an acute and fluctuating neuropsychiatric disorder characterized by impaired attention, reduced awareness of the environment, disorientation, disturbance in visuospatial ability and perception. It develops in association with another underlying medical condition (3).

Frailty and delirium are both common (4, 5) and multidimensional (6, 7). They are also strongly associated with adverse clinical events, including increased risk of functional loss, institutionalization, and mortality ([8], [9], [10]).

The relationship between frailty and delirium is not yet completely understood. Recently, a systematic review and meta-analysis summarized existing knowledge about the interplay potentially existing between these two conditions (11). From more than 1600 articles selected after an initial literature search, the authors found only twenty studies candidates for the systematic review and eight eligible for meta-analysis. It was reported a significant association between frailty and subsequent delirium, although a substantial heterogeneity was documented across the methodologies of the studies. Furthermore, the meta-analysis exclusively included studies conducted in surgical settings, none from medical wards.

It also remains largely undetermined the combined effect that delirium and frailty may exert on the patient's outcomes. In this context, it is noteworthy a recent study showing a relatively stronger association of delirium with mortality in fit versus frail patients (12).

There are also important unresolved questions regarding the relationship between the two conditions and the methods to assess delirium in frail patients. First, it is important to understand whether frailty may predispose to delirium in acute medical wards. Second, it should be explored whether frailty may also affect the patients’ performance in tests of attention that are commonly supporting the detection of delirium (13). In fact, the inability to sustain attention is a key element of delirium (3, 13). Consequently, if frailty affects delirium, it may also influence the ability to sustain attention in commonly used tests. As a result, different approaches to screening for delirium may be warranted in older patients with frailty.

The first aim of this study was to evaluate whether frailty is independently associated with the presence of delirium in a cohort of older patients admitted to an acute geriatric ward. We also sought to assess whether frailty may affect the patient's performance in three tests of attention that are commonly used in clinical practice. To this aim, we selected three tests of attention that have also been described as markers of concentration, working memory, executive function, cognitive flexibility, and central processing speed (13, 14).