Beyond the "C" in MCI: noncognitive symptoms in amnestic and non-amnestic mild cognitive impairment

How frequent and how clinically important are mood and behavioral symptoms among older adults with mild cognitive impairment (MCI)? Although these noncognitive behavioral symptoms (NCBS) are not represented in the diagnostic criteria for MCI, their clinical significance is increasingly recognized.

To address this question, the authors identified a cohort of consecutively evaluated patients from a psychiatric hospital's outpatient memory clinic. These patients' records contained both a clinical assessment and a standardized set of evaluations including the Mini-Mental State Exam, the Neuropsychiatric Inventory (NPI), and the Geriatric Depression Scale. Using a standardized chart-review approach, the presence of any NPI-screened symptom was identified and the frequencies of specific NPI-screened symptoms were calculated for the Memory Clinic MCI cohort and for amnestic and non-amnestic MCI subgroups.

A total of 116 patient records were reviewed. Thirty-eight patients with MCI were identified. Twenty-two of these met criteria for amnestic MCI by Mayo Clinic criteria while 16 met criteria for non-amnestic MCI. At least one NPI-screened mood or behavioral symptom was present in 86.8% of these MCI patients. Depression/dysphoria (63.3%), apathy (60.5%), anxiety (47.4%), irritability (44.7%), and nighttime behaviors (42.1%) were the most frequent. While depression/dysphoria was distributed similarly between amnestic and non-amnestic subgroups, apathy was significantly more frequently associated with the amnestic subtype of MCI, and nighttime behaviors were more frequently associated with the non-amnestic subtype.

Although the presence of NCBS is not required for a diagnosis of MCI, these symptoms are frequently present and constitute an important source of morbidity. Apathy and depression may be difficult to differentiate, but targeted treatment of depression may fail to address apathy. Recognizing the limitations of this preliminary study, the authors suggest that apathy may be more characteristic of amnestic MCI while nighttime behaviors may be more characteristic of non-amnestic MCI.