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LETTER TO THE EDITOR |
1 Department of Internal Medicine and Geriatrics, Helsinki University Central Hospital, Finland
2 Helsinki University Central Hospital, Unit of General Practice, Finland
3 Department of Health Sciences/Geriatrics, University of Oulu and Oulu University Hospital, Unit of General Practice, Finland
Address correspondence to Jouko Laurila, MD, PhD, Department of Internal Medicine and Geriatrics, Helsinki University Central Hospital, P.O. Box 340, 00029 HUS, Finland. Email: jouko.laurila{at}hus.fi
To the Editor:
We read with great interest the article by Bellelli and colleagues (1) regarding the survival rates of hospitalized rehabilitation patients with dementia, delirium, and dementia superimposed on dementia (DSD). The authors performed a matched, controlled study with 188 patients aged 
65 years and divided them into four groups according to the presence or absence of dementia and/or delirium during their rehabilitation period. The authors reported 1-year mortality rates of 26%, 10%, 10%, and 8% for the DSD group, dementia group, delirium group, and the group with neither condition, respectively.
Prompted by these results, we performed identical mortality analyses in our patient population collected in 1999–2000 in Helsinki, Finland. It consisted of a cohort of 425 participants aged 70 years in acute geriatric wards (n = 230), and in nursing homes (n = 195) (2). All of our participants underwent a detailed interview, and their cognitive status and prior medical history were thoroughly examined. The presence of dementia was judged globally as a consensus diagnosis of three geriatricians; delirium was assessed according to the operationalized DSM-IV criteria (3).
Of the total population, 255 individuals (60.0%) were judged to have dementia and 106 (24.9%) were suffering from delirium. DSD was diagnosed in 66 individuals (15.5% of the total population), and 130 (30.5%) had neither condition.
The survival rates of these groups were somewhat different from those reported by Bellelli and colleagues (1). The highest mortality rate in our population was found among those with delirium alone; 45% had died during the first year after the baseline assessment. Mortality was lower in the group with DSD (29%), among participants with neither delirium nor dementia (25%), and among those with dementia alone (20%) (p =.007) (Table 1). We also performed multivariate analyses using Cox proportional hazards models to clarify the prognostic significance of the delirium/dementia group. In these analyses, we used as covariates the following variables: age, gender, Charlson comorbidity index (4), and independence according to Clinical Dementia Rating (CDR)–"Personal care" (5). With the individuals without delirium or dementia as the referent group, the group with delirium alone had a significantly increased mortality risk (hazard ratio [HR] 2.10; 95% CI, 1.16–3.77; p =.014). The risk of the DSD group was not significantly increased (HR 1.24; 95% CI 0.64–2.42; p =.52). Older age (HR 1.73; 95% CI 1.12–2.66), male gender (HR 1.66; 95% CI 1.05–2.61), and Charlson comorbidity index (HR 1.18; 95% CI 1.05–1.32) were also independently associated with mortality.
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Second, our study was "real life" with exclusion of only 10.9% of all eligible patients, whereas the protocol of Bellelli and colleagues excluded most of the eligible patients. The preoperative patient selection, especially among those with elective surgery, might have skewed the population of Bellelli and colleagues towards milder cases of dementia.
In conclusion, we agree with Bellelli and colleagues that their results from patients in a postoperative rehabilitation unit may not be generalizable to individuals in other clinical settings. Delirium has been shown to be a major complication among several patient groups: postoperative patients (7), acute geriatric (2) and intensive care unit patients (8), and terminal cancer patients (9). The few studies assessing the effect of DSD on the outcome of delirium have shown controversial results (10). We still need studies assessing the survival, and factors affecting it, in different settings of delirium patients.
References
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