Summary
There is an extensive literature on SMC in older adults, and results sometimes
conflict and vary with sample size, design, and psychometric properties of measures
used. A positive relationship between SMC and objective cognitive function is
more consistently seen in larger studies that use more sensitive verbal memory
measures and in older adults without significant psychiatric symptoms. Studies
using more detailed questions about memory performance and more comprehensive
cognitive test batteries uniformly show a significant relationship between SMC and
objective cognitive function. When validated questionnaires to measure SMC and
comprehensive neuropsychological test batteries are used, the relationship between
SMC and objective cognitive performance varies by types of questions asked and
cognition domains assessed. In the majority of studies, SMC on validated ques-
tionnaires are associated with some aspect of cognitive function, including verbal
memory, working memory, and verbalfluency. One study demonstrating that
subjective complaints of attention problems relate to objective measures of this
domain, and complaints of language difficulties relate to objective performance in
this domain, suggests specificity to types of SMC. Studies thatfind only a rela-
tionship between SMC and depression might miss a true relationship between SMC
and memory performance because of too little interindividual variability in SMC
and cognitive functions. Finally, neuroimaging studies demonstrate reduced gray
matter density and hippocampal volumes, increased activation during cognitive
tasks, and increased biomarkers of Alzheimer’s disease in individuals with SMC
compared to those without SMC. These studies indicate that SMC may reflect true
changes in brain structure and function. Overall, the literature on SMC in healthy
older adults suggests that SMC do relate to objective cognitive function and are not
just reflective of psychological or personality factors.
Subjective Memory Complaints and Cognitive Decline
SMC Assessed by a Single or Few Questions with High Face
Validity
An important question in cognitively normal older adults is whether SMC are an
early sign of dementia and predict future cognitive decline. In these studies, par-
ticipants are typically assessed at baseline and then again 1 to several years later.
Analyses are conducted to determine whether baseline SMC predict either a single
objective score or rates of change in scores over time. Several longitudinal studies
show that SMC ratings based on a single or few items can be predictive of declines
in later performance.
In a study of nearly 2000 older adults, SMC, assessed withfive specific ques-
tions about a change in memory over the past decades, were associated with
288 M.T. Weber and P.M. Maki