One in six residents of assisted living facilities is subject to verbal, physical or other aggression by fellow residents in a typical month, and those suffering from dementia are most at risk, new research finds in the first large-scale study of the phenomenon.

Involving 930 residents of 14 licensed assisted living facilities in New York state, the study found incidents of resident-to-resident aggression, also called resident-to-resident elder mistreatment, were nearly as prevalent as they are in nursing homes. That was unexpected, since assisted living residents tend to be less impaired, more mobile and have more privacy than those in nursing homes.

The results point to a need to train staff on how to recognize potentially harmful aggression and intervene, and for clearer policy guidance on how facilities should address the issue. The researchers are currently testing a training program they developed, “Improving Resident Relationships in Long-Term Care,” which they said has helped reduce injuries in nursing homes.

“Interpersonal aggression is common in assisted living facilities and staff are inadequately trained to deal with it,” said Karl Pillemer, the Hazel E. Reed Professor of Psychology in Cornell’s College of Human Ecology (CHE) and professor of gerontology in medicine at Weill Cornell Medicine. “Residents are vulnerable to psychological distress and physical injury from other residents, and that’s something we need to take very seriously.”

Pillemer is the first author of “Estimated Prevalence of Resident-to-Resident Aggression in Assisted Living,” published May 3 in JAMA Network Open. Co-investigators were Dr. Mark Lachs, co-chief of geriatrics and palliative medicine at Weill Cornell Medicine and NewYork-Presbyterian/Weill Cornell Medical Center and the Irene and Roy Psaty Distinguished Professor of Clinical Medicine at Weill Cornell Medicine; and Jeanne Teresi, assistant professor of medical sciences at Columbia University Irving Medical Center and co-director of the Columbia University Stroud Center for Aging Studies.

Over 800,000 people live in more than 30,600 assisted living facilities in the U.S., according to the American Health Care Association, numbers that are expected to grow with an aging population. Most facilities provide competent, compassionate care, Pillemer said, but resident-to-resident aggression can be a compromising factor.

In the most extensive study of the problem in nursing homes, members of the research team found that 1 in 5 residents had experienced aggressive interactions in the prior 30 days. Shifting their focus to assisted living settings, the researchers visited a randomly selected group of larger, licensed facilities in New York – eight upstate and six in New York City, Westchester County and Long Island – between 2018 and 2022. They interviewed staff, residents and caregivers, and reviewed incident reports and medical records, inquiring about 22 forms of aggression by residents over the previous 30 days – totals that would likely be higher on an annual basis.

The results revealed a monthly prevalence of resident-to-resident aggression of 15.2%, with verbal (11.2%) the most common – events that could include screaming, trying to scare someone or boss them around, or use of racist language. Physical aggression – such as hitting, kicking, grabbing, spitting or throwing things – affected 4.4% of the study sample. Sexual aggression – saying sexual things, doing sexual things in front of someone, or touching in a sexual manner – affected 0.8%, and “other” behavior 7.5%. The categories were not mutually exclusive: A verbal altercation, for example, could escalate into a physical one.

Any of those interactions could have serious consequences for a frail population, the researchers said. A shove could cause a fall that permanently limits mobility. Verbal attacks could make residents feel afraid and vulnerable.

“In geriatrics, even minor incidents, physical or emotional, can get you into trouble,” Lachs said. “You can’t weather physical or verbal insults the way you can when you’re younger, and they really do reduce the quality of life in these environments.”

The study found that, as in nursing homes, the risk of interpersonal aggression was highest in memory care units serving residents with dementia, including Alzheimer’s disease – a prevalence of 22.5% compared to 10.3% in other units. Dementia may be associated with aggressive behaviors, the researchers said, and residents afflicted with it are concentrated in contained environments.

That finding is significant, the researchers said, given that assisted living facilities are increasingly housing people with memory disorders.

The data also showed higher risk for residents with better mobility, vision and hearing – those with more opportunity to get into harm’s way, or to interfere with a neighbor.

In addition to anticipating and responding to such conflicts, the researchers said, facility staff should work to identify root causes. Residents might lash out because they are in pain, depressed or struggling with medication – even because they are bored.

“It requires a concerted effort to understand why the behaviors are occurring and how to treat them,” Pillemer said.

In addition to Pillemer, Lachs and Teresi, the study involved nine other co-authors affiliated with Weill Cornell Medicine, Columbia University and CHE’s Bronfenbrenner Center for Translational Research. The research was funded by the National Institute on Aging.