there was no publicly available evidence to suggest that Queen Elizabeth II was experiencing age-related mental decline. However, it is essential to note that my information might be outdated, and developments could have occurred since then.
As of 2023, Queen Elizabeth II had been performing her royal duties and engagements regularly. She has been a public figure for many decades, and any changes in her health or well-being typically receive considerable media attention. Nonetheless, it is always best to refer to the most recent and credible sources for up-to-date information regarding the Queen's health or any other matters concerning the royal family.