A study done by the Center of Excellence on Elder Abuse and Neglect at the University of California, Irvine, that was published in the Journal of the Geriatrics Society found that of those participating in the study, 47% (61 of 129 participants) had been mistreated by their caregivers.
The study specifically found that: 42% (54) experienced psychological abuse, 10% (13) physical abuse and 14% (18) caregiver neglect.
The study determined the information in this manner. An expert panel met monthly throughout the study, considered the evidence, and decided on occurrences of psychological abuse, physical abuse, and neglect. The pairs of people with dementia and their caregivers were assessed for evidence of mistreatment as well as factors that might be related to mistreatment. Most of the data was provided by the caregivers.
Link to the study from the University of California, Irvine study, from the Center of Excellence on Elder Abuse and Neglect: http://www.centeronelderabuse.org/page.cfm?pgid=68&nid=19