The prevalence of clinically significant depressive symptoms in Alzheimer's disease: relationship with other psychological and behavioural symptoms

An increasingly literature is available on depression and depressive symptoms in Alzheimer’s disease (AD). The hypotheses explaining the occurrence of depression in AD (dAD) may be considered according to four main axes: an emotional reaction to cognitive decline, a recurrence of previous episodes of depression in the adult, vascular aetiology (vascular depression) or the neurodegenerative process which is itself causing the depressive symptoms (Lee and Lyketsos, 2003). We can estimate the dAD prevalence at around 20–40% (Arbus et al., 2003). The aim of this study is to evaluate the prevalence, associated factors and clinical correlates of depressive symptoms in AD in a sample of subjects living at home with a caregiver, and recruited through the French national network on AD (REAL.FR). The REAL.FR cohort has been described in detail in a previous article (Gillette-Guyonnet et al., 2003). Our work is a cross-sectional study. Data collected included sociodemographic data, medical and surgical history, evaluation of physical disability using the Activities of Daily Living (ADL) scale, assessment of cognitive functions with the MMSE and the ADASCog, assessment of the patient’s behavioural and psychological symptoms of dementia (BPSD) using the Neuro-Psychiatric Inventory (NPI) scale, evaluation of nutritional state by the Mini Nutritional Assessment (MNA) and evaluation of the severity stage of the dementia using the Clinical Dementia Rating (CDR) scale. Measurement of the caregiver’s subjective burden was assessed by the Zarit scale. A total of 686 subjects were enrolled. The mean age of subjects was 77.86 6.82 years. Mean scores forMMSE, the ADL scale and the total NPI were respectively 20.01 4.23; 5.43 0.90 and 15.31 15.29. There were 20.5% subjects showing clinically significant depressive symptoms (NPI 4). In comparison with the group of non-depressed subjects (NPI< 4), this subjectsweremore often women (p1⁄4 0.014), had a lower MMSE (p1⁄4 0.003), were more at risk of malnutrition (p< 0.0001) and were less often treated with a specific treatment for AD (p1⁄4 0.040). In these subjects, a personal history of depression was over-represented (p< 0.0001) and they were more often treated with antidepressants (p< 0.0001). Caregiver burden was higher in this group (p< 0.0001). Table 1 shows the correlations existing between depressive symptoms and the various neuropsychiatric symptoms. The significance threshold of 4 was retained for each BPSD. Apathy was the disorder most often seen among patients with depressive symptoms (60%), followed by anxiety (56%). Delusions and hallucinations were significantly more common in depressed subjects but in considerably lower proportions than the other disorders cited above (17% and 6.3%, respectively). A strong statistical association between depressive symptoms and anxiety is found [Odds Ratio (OR): 6.95; 95% Confidence Intervals (CI): 4.60–10.51] as well as, between depressive symptoms and irritability (OR: 3.34; 95% CI: 2.20–5.06). After multivariate logistic regression model that included gender, age and CDR score, the association between depressive symptoms and others BPSD still remained significant except for exaltation. Our study confirm that depressive symptoms are common in AD and are clinically significant in 20% of subjects. Depressed subjects showed other BPSD than depressive symptoms and their severity was more marked. In the context of evaluation of the BPSD with the NPI, the symptoms most common among patients with depressive symptoms were apathy, followed by anxiety, irritability and aggressiveness. Psychotic disorders were more common than in subjects whose INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY