We explored the influence of study partner (SP) characteristics on SP-reported neuropsychiatric symptoms (NPS) presence across the neurocognitive spectrum and on the prognostic utility of mild behavioral impairment (MBI).

We performed cross-sectional (n = 26,748) and longitudinal (n = 12,794) analyses using participant-SP dyad data from the National Alzheimer’s Coordinating Center. Participants were cognitively normal (CN; n = 11,951) or had mild cognitive impairment (MCI; n = 5686) or dementia (n = 9111).

SPs rated NPS using the Neuropsychiatric Inventory Questionnaire. We used multivariable logistic regression to model the association between SP characteristics (age, sex, and relationship to participant [spouse, child, and other]) and NPS status (outcome). Cox regressions assessed SP characteristics as moderators of MBI associations with incident dementia or as predictors of incident dementia in MBI + participants only.

Among CN persons, younger, female, and spouse SPs reported NPS more frequently. In MCI, younger SPs and those who were spouses or children of participants reported higher NPS odds. For dementia participants, NPS odds were higher in female and spouse SPs. MBI associations with incident dementia were slightly weaker when SPs were older but did not depend on SP sex or relationship to participant. Among MBI + participants with spouse or child SPs, hazard for dementia was higher when compared to MBI + participants with other SPs.

SP age, sex, and relationship to participant influence NPS reporting across the neurocognitive spectrum, with potential implications for MBI prognosis. Considering SP characteristics may enhance the accuracy of NPS assessments, which may facilitate therapy planning and prognosis.

Informant-based questionnaires may have utility for cognitive impairment or dementia screening. Reviews describing the accuracy of respective questionnaires are available, but their focus on individual questionnaires precludes comparisons across tools. We conducted an overview of systematic reviews to assess the comparative accuracy of informant questionnaires and identify areas where evidence is lacking.

We searched six databases to identify systematic reviews describing diagnostic test accuracy of informant questionnaires for cognitive impairment or dementia. We pooled sensitivity and specificity data for each questionnaire and used network approaches to compare accuracy estimates across the differing tests. We used grading of recommendations, assessment, development and evaluation (GRADE) to evaluate the overall certainty of evidence. Finally, we created an evidence ‘heat-map’, describing the availability of accurate data for individual tests in different populations and settings.

We identified 25 reviews, consisting of 93 studies and 13 informant questionnaires. Pooled analysis (37 studies; 11 052 participants) ranked the eight-item interview to ascertain dementia (AD8) highest for sensitivity [90%; 95% credible intervals (CrI) = 82–95; ‘best-test’ probability = 36]; while the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) was most specific (81%; 95% CrI = 66–90; ‘best-test’ probability = 29%). GRADE-based evaluation of evidence suggested certainty was ‘low’ overall. Our heat-map indicated that only AD8 and IQCODE have been extensively evaluated and most studies have been in the secondary care settings.

AD8 and IQCODE appear to be valid questionnaires for cognitive impairment or dementia assessment. Other available informant-based cognitive screening questionnaires lack evidence to justify their use at present. Evidence on the accuracy of available tools in primary care settings and with specific populations is required.

Relative to dementia, little is known about informant bias in mild cognitive impairment (MCI). We investigated the influence of informant demographic and relational characteristics on reports of everyday functioning using the Functional Activities Questionnaire (FAQ).

Four thousand two hundred eighty-four MCI participants and their informants from the National Alzheimer’s Coordinating Center Uniform Data Set were included. Informants were stratified according to cohabitation, relationship, visit frequency, race/ethnicity, education, and sex. Informant-rated Mean FAQ score was compared across these groups using univariate general linear model analyses and post hoc tests. Interactions were tested between informant variables. The predictive contribution of informant variables to FAQ score was explored using hierarchical linear regression. Analyses covaried for participant cognition using a cognitive composite score, and for participant age, sex, and depression.

After controlling for participant cognition, depression, age, and sex, informant-rated FAQ scores varied significantly across all informant variables (p’s < .005, ηp2’s ≤ .033) except sex and visit frequency. FAQ scores were higher (more impaired) among informants who cohabitate with the participant, among paid caregivers, spouses, and adult children, and among informants with higher levels of education. Scores were lowest (less impaired) among Black/African American informants as compared to all other racial/ethnic groups.

Demographic and relational characteristics of informants influence the perception and reporting of instrumental activities of daily living in adults with MCI. As everyday functioning is crucial for differential diagnosis and treatment outcome measurement, it is important to be aware of sources of informant report discrepancies.