A Collaborative Study of the Emergence and Clinical Features of the Major Depressive Syndrome of Alzheimer’s Disease
Zubenko GS, Zubenko W, McPherson S, Spoor E, Marin DB, Farlow MR, Glenn E. Smith, et al.;
Commented by , 24 Jun 2003
Aim of the Study
To evaluate the prevalence and clinical features of major depression in Alzheimer’s disease.
Methods
This is a collaborative study between 3 neurology research sites and 2 psychiatry research sites in the USA. All sites administered the Clinical Assessment of Depression in Dementia (CADD) to samples of known patients fulfilling NINCDS-ARDRA criteria for probable Alzheimer’s disease. A total of 243 out-patients were recruited from the 5 sites.
The CADD is a structured assessment tool, developed by this research group, comprising 17 items of the Hamilton Depression Rating Scale, a subsection of the Neuropsychiatric Inventory rating delusions and hallucinations, and a section of the Structured Clinical Interview for DSM-III-R appropriate to this patient group. Raters (experienced clinicians) interviewed patients and caregivers after training in the use of CADD.
A control group of 151 nondemented elderly community volunteers underwent an identical assessment, 43 of whom fulfilled diagnostic criteria for major depression.
Results
The prevalence of major depression as assessed by CADD varied considerably between the sites, from 22.5 % at the Mayo Clinic to 55.4 % recruited at the National Institute of Mental Health site. Clinical features of depression were slightly different in demented subjects, who exhibited poor concentration and indecisiveness, but less sleep disturbance and feelings of guilt and worthlessness than nondemented controls.
Compared to Alzheimer’s subjects without depression, those with major depression had onset of dementia at a younger age and were more likely to experience psychotic phenomena. However, the average severity of the major depression, reflected by a mean Hamilton score of 12.9, was low compared to previous studies on in-patient populations. 24 of the 44 subjects with major depression were on antidepressant treatment at the time of study.
The onset of major depression was commonest in early Alzheimer’s disease, consistent with previous literature, though most of these subjects had no past history of depression.
Discussion
Major depression at, or after, the onset of cognitive impairment is common in older patients with Alzheimer’s disease, certainly much commoner than in controls. Using a structured tool such as the CADD is likely to improve diagnostic certainty, though its use is more practicable in research than in clinical practice.
The wide range of prevalence of depression was an unexpected finding, which may reflect sampling issues. There was a trend favouring higher prevalence of depression at the psychiatry-based recruitment sites (Mount Sinai and the NIMH) than the neurology-based ones, though this did not reach statistical significance.
This study provides supporting evidence that major depression in Alzheimer’s disease is a distinct entity that is among the most common mood disorders of old age.