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Subsyndromal Delirium in Older People: A Systematic Review of Frequency, Risk Factors, Course and Outcomes
Martin G. Cole; Antonio Ciampi; Eric Belzile; Marika Dubuc-Sarrasin
FOCUS 2013;11:534-543. doi:10.1176/appi.focus.11.4.534

Objective  To determine the frequency, risk factors, course and outcomes of subsyndromal delirium (SSD) in older people by systematically reviewing evidence on these topics.

Methods  Subsyndromal delirium was defined as the presence of one or more symptoms of delirium, not meeting criteria for delirium and not progressing to delirium. MEDLINE, EMBASE, PsycINFO and the Web of Science were searched for potentially relevant articles published from 1996 to June 2011. The bibliographies of relevant articles were searched for additional references. Twelve studies met the inclusion criteria. The validity of included studies was assessed according to Evidence-Based Medicine criteria. Information about the study population and methods, age, gender, proportion with dementia, diagnostic criteria, period and frequency of observation, and the topics above was systematically abstracted, tabulated and synthesized using standard meta-analysis techniques.

Results  The combined prevalence of SSD was 23% (95% CI, 9–42%); the combined incidence was 13% (95% CI, 6–23%). Risk factors were similar to those for delirium. Episodes lasted up to 133 days and were often recurrent. Outcomes were poor and often intermediate between those of older people with or without delirium. Of note, there was significant unexplained heterogeneity in the results of studies of prevalence, incidence and some risk factors.

Conclusions  SSD in older people may be a frequent and clinically important condition that falls on a continuum between no symptoms and full delirium. Because of significant unexplained heterogeneity in the results of studies of SSD, however, the results of this review must be interpreted cautiously. Further research is necessary. Copyright © 2012 John Wiley & Sons, Ltd.
(Reprinted with permission from International Journal of Geriatric Psychiatry 2013; 28:771–780) 

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Figure 1. Individual and Combined Prevalence and Incidence Rates of Subsyndromal Delirium (and 95% Confidence Interval (95% CI)).

Figure 2. Individual and Combined Odds Ratio (OR) (and 95% Confidence intervals (95% CI)) in Studies of Risk Factors for Incident Subsyndromal Delirium. BADL, Basic Activities of Daily Living.

Figure 3. Individual and Combined Odds Ratio (OR) (and 95% Confidence Intervals (95% CI)) in Studies of Outcomes of Subsyndromal Delirium.
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Table 1.Summary of Studies of the Frequency of SSD
Table Footer Note

CAM, Confusion Assessment Method; (est), estimated; GU, geriatric unit; ICDSC, Intensive Care Delirium Screening Checklist; ICU: intensive care unit; LTC, long-term care; MI, medical inpatient; P, palliative care; SDU, step-down unit; SI, surgical inpatient; SSD, subsyndromal delirium.

Table Footer Note

a Combined prevalence and incidence

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Table 2.Summary of Studies of Risk Factors and Outcomes for SSD
Table Footer Note

APS, Acute Physiology Score; CAM, Confusion Assessment Method; ICSDSC, Intensive Care Delirium Screening Checklist; GU, geriatric unit; MI, medical inpatient; SI, surgical inpatient; BADL, basic activities of daily living; I, incident; P, prevalent; SSD, subsyndromal delirium; CCI, Charlson Comorbidity Index; ICU, intensive care unit; LTC, long-term care; SDU, step-down unit.

Table Footer Note

a Risk factors for combined prevalent and incident SSD.



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