Subjective cognitive decline a red flag for Alzheimer’s disease

Subjective cognitive decline appears to be indicative of stage 2 Alzheimer’s disease (AD), where individuals exhibit mild changes in mood or behaviour and subtle objective cognitive decline although not to the point of meeting mild cognitive impairment (MCI) criteria, as suggested in a study.

The study used cross-sectional and longitudinal data from the multicentre, memory clinic–based DELCODE study and included 445 individuals with SCD (average ae 70 years) and 200 adults without SCD and whose cognitive performance was within the normal range (control). 

Researchers looked at the baseline and at follow-up data for Clinical Dementia Rating (CDR), the 15-item Geriatric Depression Scale (GDS), the short version of the Geriatric Anxiety Inventory (GAI-SF), the Neuropsychiatric Inventory (NPI-Q), and the Functional Activities Questionnaire (FAQ). They conducted the structured subjective cognitive decline interview (SCD-I) to assess subjectively experienced changes in cognition, as well as measured the Mini-Mental State Examination (MMSE) and the Free and Cued Selective Reminding Test Immediate Recall (FCSRT-IR) scores and the Preclinical Alzheimer's Cognitive Composite (PACC5).

Compared with control, the SCC group tended to be older and showed slightly worse performance on the CDR sum of boxes (CDR-SOB; p<0.001), the PACC5 (p<0.001), the FCSRT (p<0.001), as well as on the factor scores of memory (p<0.001), language abilities (p<0.012), and executive function (p=0.03). There were also significant between-group differences in the FAQ, SCD-I, GDS, GAI, and the NPI scores (p<0.001 for all).

Among participants with amyloid positivity, those with SCD showed greater hippocampal atrophy, lower cognitive and functional performance, and more behavioural symptoms compared with controls. Amyloid concentration in the cerebrospinal fluid was associated with a greater effect on longitudinal cognitive decline in SCD than in the control group.

The findings have important clinical implications, in that it helps to identify individuals who are a promising target for early intervention today, as well as aid in early disease identification and treatment in the future.