We aimed to prospectively assess the change in neuropsychiatric symptoms among people who develop cognitive impairment and have a history of post-traumatic stress disorder (PTSD). We analyzed longitudinal data from the National Alzheimer's Coordinating Center Unified Data Set (March 2015 to December 2021). Analyses included individuals who were cognitively normal and who had nonmissing assessment of PTSD at the initial visit and had at least 1 follow-up visit with cognitive impairment. We compared the difference in the mean neuropsychiatric symptom score at the first Unified Data Set visit versus the first visit with a Clinical Dementia Rating of 0.5 between those with and without a history of PTSD. The mean neuropsychiatric symptom score change did not differ between those with and without a history of PTSD (1.06 vs. 0.77, respectively; P =0.79). The null results found in this study warrant future research. Several methodological limitations might explain these results.