Mild Behavioral Impairment and Subjective Cognitive Decline predict Mild Cognitive Impairment

Objective: Better methods for detecting preclinical neuropathological change are required for prevention of dementia. Mild behavioral impairment (MBI) and subjective cognitive decline (SCD) can represent neurobehavioral and neurocognitive axes of early stage neurodegenerative processes, which are represented in Stage 2 of the NIA-AA Alzheimers disease research framework. Both MBI and SCD may offer an opportunity for premorbid detection. We test the hypothesis that MBI and SCD confer additive risk for incident cognitive decline. Methods: Participants were cognitively normal older adults followed up approximately annually at Alzheimers Disease Centers. Logistic regression was used to determine the relationship between baseline classification (MBI+, SCD+, neither (MBI-SCD-), or both (MBI+SCD+)) and cognitive decline, defined by Clinical Dementia Rating (CDR) total score, at 3 years. Results: Of 2769 participants (mean age=76; 63% females), 1536 were MBI-SCD-, 254 MBI-SCD+, 743 MBI+SCD-, and 236 MBI+SCD+. At 3-years, 349 individuals (12.6%) developed cognitive decline to CDR>0. Compared to SCD-MBI-, we observed an ordinal progression in risk, with ORs [95% CI] as follows: 3.61 [2.42-5.38] for MBI-SCD+ (16.5% progression), 4.76 [3.57-6.34] for MBI+SCD-, (20.7% progression) and 8.15 [5.71-11.64] for MBI+SCD+ (30.9% progression). Conclusion: MBI in older adults alone or in combination with SCD is associated with a higher risk of incident cognitive decline at 3 years. The highest rate of progression to MCI is observed in those with both MBI and SCD. Used in conjunction, MBI and SCD could be simple and scalable methods to identify patients at high risk for cognitive decline for prevention studies.