Synonyms

Blessed dementia rating scale (BDRS); Blessed-Roth DS; Dementia scale (DS); Modified Blessed dementia scale (DS); Newcastle DS; Revised dementia scale (RDS)

Description

The Blessed dementia scale (DS) was developed in 1968 by Blessed and colleagues in an attempt to quantify the “degree of intellectual and personality deterioration” (p. 799) in the elderly.

This rating scale consists of 22 items that reflect (1) changes in performance of everyday activities (8 items; e.g., using money and finding one’s way), (2) changes in habits including self-care (3 items; i.e., eating, dressing and continence), and (3) changes in personality, interests, and drives (11 items; e.g., evaluation of rigidity and affect). A close friend or relative is asked to provide these behavior ratings of the examinee over the past 6 months; when unavailable, medical records can be used. The DS is scored on a 0–28-point scale, where higher numbers indicate a larger decrement in functional capacity. On everyday activity items, a score of 1 is given for total inability to perform a task; a score of 0.5 is given for partial, variable, or intermittent inability to perform an activity; and a score of 0 is given if the patient is able to perform the task. The changes in habits section are scored on a 4-point scale (i.e., 0–3), resulting in a stronger contribution to the total score. Personality changes are scored 1 if present or 0 if absent (Blessed et al. 1968, 1988). A total cutoff score of 4 out of 28 is typically used to differentiate patients with dementia versus those without. Scores of 4–9 indicate mild impairment, whereas scores of 10 or higher suggest moderate to severe impairment (Eastwood et al. 1983). Stern et al. (1987) have suggested 15 as the threshold for moderate impairment.

The original DS also included a second section comprised of a brief battery of simple cognitive tasks, called the information-memory-concentration test (IMCT; Blessed et al. 1968, 1988). Similar to other brief mental status instruments, the IMCT incorporates 12 items of information/orientation, 11 items of long-term memory, a brief test for the 5-min recall of a person’s name and address, and 3 sequencing tasks requiring concentration (Blessed et al. 1968, 1988). This sub-component is typically no longer included in the DS.

Historical Background

The original dementia scale (DS) evaluated informant-reported changes in behavior and daily functioning and also included cognitive tasks given to the patient. It was developed by Blessed, Tomlinson, and Roth in 1968 in an attempt to compare the deterioration of intellect and personality with underlying brain neuropathology (Blessed et al. 1968, 1988). The revised dementia scale (RDS) was introduced in 1988 and included only items reflecting informant-rated changes in everyday activities and habits (items 1 through 11; Erkinjuntti et al. 1988). The sensitivity and specificity of the revised scale was higher than that of the original DS, possibly due to lower dementia specificity of the excluded items (i.e., changes in personality, interests, and drive; Lawson et al. 1977). However, the 4-week test-retest reliability for the revised scale was lower (r = 0.68) than the original (r = 0.79), potentially due to the inclusion of fewer items (Erkinjuntti et al. 1988).

Items from the DS have been included in the standardized interview with relatives that is part of the Cambridge Mental Disorders of the Elderly Examination (CAMDEX; Roth et al. 1986). Elements of this scale have also been incorporated in the standardized battery of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD; Morris et al. 1988). Additional analysis of the scale has indicated that the items can be subdivided into four groups, each with its own score (cognitive, items 1–7, score range 0–7; personality change, items 12–17, score range 0–6; apathy/withdrawal, 18, 20, and 21, score range 0–3; basic self-care, 9–11, score range 0–3), in order to aid in interpretation (Stern et al. 1990).

Psychometric Data

In community-dwelling individuals, test-retest reliability after 4 weeks was r = 0.79; the first 11 items show marginal reliability (r = 0.68; Erkinjuntti et al. 1988). Cole (1990) found an interrater reliability of r = 0.59 when comparing DS ratings by two independent raters who each interviewed the caretakers of 47 dementia patients.

The initial study employing the DS showed that scores increased as the presence of senile plaques increased (r = 0.77; Blessed et al. 1968). Also, the DS showed discriminative validity in identifying senile dementia patients compared with depressed, paraphrenia, delirious, and physically ill patients (Blessed et al. 1968). Others have also noted that the DS is able to discriminate between dementia patients and community residents (Erkinjuntti et al. 1988; Lam et al. 1997). When a cutoff of 4/28 was used, the DS was shown to have a sensitivity of 90% and a specificity of 84% (Erkinjuntti et al. 1988). Moderate to high correlations have been reported with other measures such as the CERAD total score (r = 0.40; Chandler et al. 2005), the Mini-Mental State Exam (r = 0.80; Hendrie et al. 1988), and the CAMDEX (r = 0.77; Hendrie et al. 1988). Additionally, Stern et al. (1987) reported that disease progression can be monitored using the DS; cognitive deficiencies affecting instrumental activities of daily living (e.g., handling money, remembering short lists) were evident early and worsened throughout the disease course, whereas changes in basic self-care did not occur until 4–5 years into the illness (Stern et al. 1990).

A cutoff of 1.5 on the RDS yields a sensitivity of 93% and a specificity of 97% in discriminating between demented and non-demented subjects, regardless of level of dementia (Erkinjuntti et al. 1988). The RDS is also highly correlated with the Activities of Daily Living Scale, the Instrumental Activities of Daily Living Scale, and the Functional Activities Questionnaire (Juva et al. 1997).

The DS appears minimally affected by demographic factors. Age correlates moderately with DS scores (r = 0.31), but when degree of dementia is taken into account, age does not have a significant effect (Erkinjuntti et al. 1988). Education appears unrelated to DS scores (Erkinjuntti et al. 1988). African-American patients score higher on the DS than white patients (Hargrove et al. 1998). The DS has been translated and validated in Chinese, Korean, and Czech (Lam et al. 1997; Lee et al. 1999; Vajdickova et al. 1995).

Clinical Uses

The DS offers a blend of items commonly found on mental status exams, activities of daily living scales, and instrumental activities of daily living scales. It is quick and easy to administer and additionally provides a quantification of the degree of dementia severity. As such, it is ideal for use by general practitioners and specialized medical and mental healthcare professionals to gauge initial status, as well as to track disease progression. The DS may also provide more useful information in a clinical setting than the MMSE and other cognitive assessment scales (Mant et al. 1988) because it measures functional aspects of dementia.

Cross-References