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Objectives Subjective cognitive decline (SCD) is a known risk factor for Alzheimer's disease. However, little research has examined whether healthy older adults with SCD (SCD+) exhibit lower cognition and increased rates of cognitive decline compared to those without SCD (SCD−). The goal of this study was to examine if cognitive change over a 15-year period differs between SCD+ and SCD−. Method 3,019 cognitively normal older adults (831 SCD+) from 3 Rush Alzheimer's Disease Center cohort studies were followed annually for up to a maximum of 15 years. Due to attrition, the average follow-up time was 5.7 years. Cognition was measured using z-scores of global cognition, episodic memory, semantic memory, perceptual speed, visuospatial ability, and working memory. Linear mixed-effects models investigated whether SCD was associated with cognitive change. Results Both baseline cognition and cognitive change over time differed between SCD+ and SCD−. People with SCD+ exhibited lower baseline scores and a steeper decline in global cognition, episodic memory, semantic memory, and perceptual speed. People with SCD+ did not differ from SCD− in baseline visuospatial ability or working memory but exhibited increased change over time in those two domains compared to SCD−. Discussion The observed results reveal that older adults with SCD+ have lower baseline cognition and steeper declines in cognition over time compared to SCD−. Older adults with SCD may be aware of subtle cognitive declines that occur over time in global cognition, episodic memory, semantic memory, perceptual speed, visuospatial ability, and working memory compared to those without SCD. [ABSTRACT FROM AUTHOR]