Understanding Subsyndromal Delirium: A Precursor to Delirium

In the October 2011 AGS Viewpoint, “Understanding Subsyndromal Delirium: A Precursor to Delirium” (page 10), the number of residents who met the criteria for subsyndromal delirium (SSD 1) was listed incorrectly as 58 of 104. It should have indicated 68 of 104. The sentence, which appears in the last paragraph in the second column, should have read: “During the study, 68 of the 104 residents met the criteria for SSD 1, indicating an incidence of 5.2 per 100 person-weeks of observation.” We regret the error.
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Delirium (acute confusional state) is common in long-term care (LTC) facilities, hospitals, and other institutional settings, but is often overlooked, despite being associated with high mortality rates among people ≥65 years of age. During the Henderson State-of-the-Art Lecture at the 2011 American Geriatrics Society (AGS) Annual Scientific Meeting in May, Sharon K. Inouye, MD, MPH, director, The Aging Brain Center, Hebrew SeniorLife, and professor of medicine, Harvard Medical School, noted that the risk of mortality remains high even after individuals are discharged from acute care settings, with rates ranging from 35% to 40% at 1 year postdischarge.¹ However, delirium is not an unavoidable complication of being admitted to these settings. Research and educational efforts, including those by the AGS,² are advancing our understanding of delirium and raising awareness that many cases can be prevented. However, to make a maximal dent in reducing the incidence of delirium and its associated complications, a related, common, and perhaps even more frequently overlooked threat must be addressed: subsyndromal delirium (SSD; the presence of subthreshold symptoms of delirium).

Considerably less is known about SSD than delirium, and there are no agreed upon criteria for its diagnosis. Currently, a variety of diagnostic protocols are used, including the popular Confusion Assessment Method (CAM), which was designed to enable nonpsychiatrically trained clinicians to quickly and accurately identify delirium. CAM assesses for core symptoms and characteristics of delirium, including inattention, disorganized thinking, altered level of consciousness, acute onset, and fluctuation of symptoms.

Regardless of how SSD is diagnosed, it has been consistently linked with poor outcomes, including cognitive decline, functional losses, extended hospital stays, higher risks of admission to LTC facilities, and death, report Martin G. Cole, MD, McGill University, and colleagues, in an invaluable new study published in the Journal of the American Geriatrics Society.³ The article, which examines SSD in LTC facilities, followed 104 LTC residents (≥65 years of age) in Montreal and Quebec City for 6 months. All residents were free of core symptoms of delirium at the start of the study, as determined through the use of CAM, the Mini-Mental State Examination (MMSE), Delirium Index (DI), Hierarchic Dementia Scale, and Barthel Index at baseline. Each subsequent week, the authors reassessed residents using CAM, MMSE, and DI.

To determine how differing diagnostic criteria might have an impact on SSD incidence, the researchers followed a protocol developed by other researchers, which classified residents with one or more core symptoms of delirium on CAM as having SSD 1 and those with two or more core symptoms as having SSD 2, a more advanced  form.

During the study, 68 of the 104 residents met the criteria for SSD 1, indicating an incidence of 5.2 per 100 person-weeks of observation. The incidence of SSD 2 was lower at 1.3 per 100 person-weeks of observation. Although previous studies in acute care settings have found that SSD 1 is consistently associated with poor outcomes, Cole and colleagues found that “the differences in outcomes between residents with and without SSD 1 were small and not statistically significant.” In contrast, residents with SSD 2 had worse cognitive outcomes than those without SSD, a finding that was statistically significant. 

Cole and colleagues conclude that “despite limited statistical power, [their] findings have potentially important implications for clinical practice and research in LTC settings.” They note that their study supports “the notion of a continuum of acute neurocognitive disorder ranging from no delirium to full delirium, where a range of risk factors and symptoms may be quantitatively related to adverse outcomes.” This suggests that identifying residents with or at risk of developing SSD 2, and targeting these residents for interventions that have been effective in preventing and treating delirium in acute care settings, may be warranted. “Given the cost associated with managing behavior problems in [LTC] settings, successful interventions could not only prevent complications of SSD, but also help lessen burden on staff and lower costs of care,” the authors write.

References

1. American Geriatrics Society. Preventing and effectively treating delirium in elderly can save seniors’ lives and may also lower their risks of permanent cognitive loss, notes Sharon Inouye, MD, recipient of American Geriatrics Society’s Henderson State-of-the-Art Award. Accessed September 28, 2011.

2. American Geriatrics Society. Addressing delirium–an interdisciplinary acute care for elderly (ACE) approach. Accessed September 28, 2011.

3. Cole MG, McCusker J, Voyer P, et al. Subsyndromal delirium in older long-term care residents: incidence, risk factors, and outcomes. J Am Geriatr Soc. https://onlinelibrary.wiley.com/doi/10.1111/j.1532-5415.2011.03595.x/abstract. Accessed September 28, 2011.