Standardized Assessment Tools

Due to the high frequency of depressive symptomatology, we advocate the use of depression rating scales in clinical practice for mental status examination as symptom checklists and to measure severity of symptoms in an individual patient. However, because the commonly used depression rating scales are not specifically designed to score the abovementioned symptoms that are prevalent in predementia, we cannot recommend the use of traditional cutoff scores in deciding whether a patient is depressed or not. With this in mind, we use the HDRS (17-item, clinician- based) [11] , the Geriatric Depression Scale (15-item, self-rating) [12] , and the Neuropsychiatric Inventory (12-item, informant-based) [13], which in our opinion is a good composition of well-known and validated scales for measuring depressive symptomatology from several perspectives in a memory clinic setting.

Epidemiological Aspects

In both people with dementia and MCI, affective symptoms are very common and cause a severe burden for patients and their caregivers. Previous studies among people with AD dementia found that 80-90 % of the people reported neuropsychiatric symptoms. Findings from a large study of 12 centers from the European Alzheimer’s Disease Consortium found affective symptoms, such as depression and anxiety, to be very common in dementia [14].

In people with MCI, prevalence rates of neuropsychiatric symptoms range from 35 to 75 % [15], again with depression, anxiety, apathy, and irritability being most common. The large range in prevalence rates can be explained by several factors: a wide diversity in study characteristics, such as different sampling methods, different settings, differences in MCI definitions, or the sensitivity of the instruments used to measure neuropsychiatric symptomatology. Higher prevalence rates were found in hospital-based samples (median value 44 %) compared to population-based cohorts (median value 16 %) [16]. More specifically, Monastero et al. [17] found depressive symptoms to be present in 9-78 % of the MCI patients attending hospital-based settings, with highest prevalence rates for subjects directly attending a memory clinic. A recent study into social and demographic factors that might influence affective symptoms in MCI, including data from 3456 participants, showed that a higher presence of depressive symptoms in MCI was related to younger age, female gender, lower education, not being married, a Caucasian ethnicity, and more functional impairment [18]. Additionally, several studies investigated whether specific cognitive profiles, such as amnestic or non-amnestic subtypes of MCI, were related to specific affective symptoms, but results remained inconsistent [19-21].

On the other hand, cognitive deficits in people with depression are widespread and not limited to memory. Christensen et al. [22] found cognitive deficits in depressed people in almost every cognitive test, with an average deficit of 0.63 standard deviations compared to nondepressed people. However prevalence rates about MCI in people with depressive symptomatology remain unclear [23].

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