Age and Ageing Advance Access originally published online on March 28, 2008
Age and Ageing 2008 37(3):353-354; doi:10.1093/ageing/afn056
Delirium in older people: an epiphenomenon of incipient death or a separate biological process?
SIR—The paper by Adams et al., published in Age and Ageing [1], shows that Mini Mental State Examination (MMSE) scores, albumin serum levels and biomarkers of inflammation, but not delirium, are associated with 6-month mortality of medical inpatients. We would discuss this topic with our data, referring to 1,811 patients (
65 years) discharged from a Rehabilitation and Aged Care Unit (RACU) between May 2003 and April 2006, and followed up at 12 months. All patients were evaluated on admission with a multi-dimensional assessment including age, gender, living arrangement, MMSE scores, Charlson Index, albumin and C-reactive protein (CRP) serum levels and Instrumental Activity of Daily Living (IADL) scores [2], referenced to 1 month before admission. The diagnosis of delirium was obtained with the Confusion Assessment Method [3], while dementia was defined according to DSM III-R criteria [4]. Delirium was detected in 239 (13.2%) individuals: 71 (29.7%) had delirium alone while 168 (70.7%) had delirium superimposed on dementia (DSD). Subjects with DSD were oldest, had the greatest comorbidity, the lowest albumin and the highest CRP serum levels, the worst MMSE and IADL scores and the highest rate of 12-month mortality, in comparison with the other groups (Table 1).
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To test the hypothesis of the report by Adams et al., we performed two multiple logistic regressions with mortality as the dependent variable. In the first regression, potential predictors were: age, gender, Charlson Index, CRP and albumin serum levels, MMSE and IADL scores and delirium (presence or absence). In the second, DSD was included as possible predictor in place of delirium. The first regression showed that age (odds ratio [OR] =1.07, 95% confidence intervals [CI] 1.04–1.10, P < 0.0005), Charlson Index (OR = 1.33, 95% CI 1.2–1.4, P < 0.0005) and MMSE (OR = 1.06, 95% CI 1.02–1.09, P < 0.005) were the only significant predictors. In the second regression, age (OR = 1.07, 95% CI 1.04–1.10, P < 0.0005), Charlson Index (OR = 1.33, 95% CI 1.23–1.44, P < 0.0005), and MMSE (OR = 1.06, 95% CI 1.03–1.09, P < 0.0005) maintained their original significance, but DSD (OR = 1.69, 95% CI 1.14–2.76, P = 0.03) was also found to be a significant and independent predictor of 12-month mortality.
Our data only partially agree with those of Adams et al., showing that poor cognition, comorbidity and old age—but not delirium—predict mortality. According to these results, delirium could be regarded as a clinical epiphenomenon of incipient death rather than as a separate biological process. However, the results of the second regression suggest that when delirium is superimposed on dementia, it exerts an autonomous effect on mortality, independently from cognition and other related factors. We believe that DSD should be regarded as a separate pathophysiological entity; it can be hypothesised that a chain of adverse metabolic reactions, accompanying delirium in demented patients, can impair patients' homeostasis and lead to increased mortality through self-maintaining physiopathological mechanisms [5].
1 Rehabilitation and Aged Care Unit, "Ancelle della Carità" hospital, Cremona, Italy
2 Geriatric Research Group, Brescia, Italy
3 University Tor Vergata, Rome, Italy
* To whom correspondence should be addressed E-mail: giuseppebellelli{at}libero.ita; bellelli-giuseppe{at}ancelle.it
References
- Adams D, Treloar A, Darwiche F, et al. Association of delirium with in-hospital and in 6-months mortality in elderly medical inpatients. Age Ageing (2007) 36:644–9.
[Abstract/Free Full Text] - Lawton MP, Brody EM. Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist (1969) 9:179–86.[Web of Science][Medline]
- Inouye SK, Van Dyck CH, Alessi CA, et al. Clarifying confusion: the confusion assessment method. Ann Intern Med (1990) 113:941–8.
[Abstract/Free Full Text] - American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (1987) 3rd edition. Washington, DC: American Psychiatric Association.
- Bellelli G, Frisoni GB, Turco R, et al. Delirium superimposed on dementia predicts 12-month survival in elderly patients discharged from a postacute rehabilitation facility. J Gerontol A Biol Sci Med Sci (2007) 62:1306–9.
[Abstract/Free Full Text]
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