There is no standardized test used to measure dementia secondary to use of Statins.
Dementia may have many eitiologies. Statins dissolve cholesterol,
and memories are stored in a similiar class of substances. In some patients Statins are absolutely necessary, but they are often overprescribed. There is sufficient literature on the internet that will enable you to make your own decision. As Red_Star stated, there are more than five good reasons not to worry about cholesterol.