A memory complaint, also called Subjective Cognitive Decline (SCD), is a subjective disorder that appears to be relatively common, especially in elderly persons. The reports of its prevalence in various populations range from approximately 10% to as high as 88%, although it is generally thought that the prevalence of everyday memory problems lie within the range of 25% to 50%.

https://www.sciencedaily.com/releases/2017/11/171113095443.htm