Those found to have MBI, with and without SCD, did poorer overall on trails A and B tests.
In a cohort of midlife adults, mild behavioral impairment may be a reliable marker for impaired executive function, regardless of subjective cognitive decline, in the early stage of Alzheimer's disease, according to a presenter.
"Both [subjective cognitive decline] and [mild behavioral impairment] have been added as diagnostic categories to the [Uniform Data Set, version four]," Carol A. Van Hulle, PhD, associate scientist in the division of geriatrics and gerontology in the department of medicine at the University of Wisconsin School of Medicine and Public Health, told attendees at the Alzheimer's Association International Conference.
"This is a uniform protocol that is adopted by all the Alzheimer's disease research centers in the United States and the National Institute of Aging and Alzheimer's Association," Van Hulle said.
Clinical staging for AD includes both mild behavioral impairment (MBI) and subjective cognitive decline (SCD) separately as indicators of transitional decline, defined as minimal cognitive change with negligible impact on daily function, she continued.
As such, Van Hulle and colleagues hypothesized that unimpaired individuals experiencing both conditions would demonstrate steeper declines across standard measures of cognitive performance.
They analyzed 320 enrollees from the Wisconsin Alzheimer's Disease Research Center's clinical core (mean age, 61.6 years; 69.3% female) who were cognitively unimpaired and completed the necessary SCD and neuropsychiatric testing over at least two study visits.
Researchers attempted to ascertain the presence or absence of both conditions over the first four clinical visits.
SCD was measured by the Geriatric Depression Scale (GDS) score where answers in the affirmative during at least two of four visits indicated positive status (SCD+), with negative status (SCD-) revealed without recollection of memory issues at any of the initial visits. MBI was assessed via the Neuropsychiatric Inventory Questionnaire (NPI-Q), where scores of 1 or more at two consecutive visits indicated MBI-positive (MBI+) status.
The primary outcomes were the immediate and delayed recall scores for the timed Rey Auditory Verbal Learning test, along with those from the trails A and B time tests.
Based on GDS scores, the most populous of the four subgroups were those who were both SCD and MBI negative (71%), with the second most populous SCD-/MBI+ (18%), Those who were either SCD+/MBI- or SCD+/MBI+ were at 6% each.
The researchers also found that those who were SCD+/MBI+ had the quickest and steepest decline with linear age in immediate recall compared with the other three groups, while those who were SCD-/MBI- also registered a steep, though less significant decline.
However, they noted no other significant interactions between the SCD and MBI groups and age for any other outcomes.
Data also showed what Van Hulle called a "very modest main effect" on both the trails A and B tests. When controlling for age, participants in the SCD+/MBI+ positive group performed worse comparatively than a reference group on trails A. Similarly, people in the SCD+/MBI- group and the SCD+/MBI+ groups performed slightly worse than the reference group on trails B.
As a result, Van Hulle said that these data did not support her original hypothesis that unimpaired individuals with MBI and SCD would experience steeper declines in cognitive performance, but she would like to see further research.
"The field in general is moving away from single measures of subjective cognitive complaints," she added. "And so, what I'd like to do is use a more comprehensive measure for the subjective cognitive complaint part of this analysis."