A rise in reported abuse of nursing home residents is fueling calls for tougher minimum staffing requirements for registered nurses at the facilities.

Only 5% of nursing homes have adequate staffing, said Charlene Harrington, professor emeritus at the University of California San Francisco School of Nursing. Finding and retaining staff has proved tough because caregivers can earn more in hospital settings that have better working conditions.

The shortfall could be putting residents at risk. Reported incidents of physical, verbal, and sexual abuse involving nursing home residents more than doubled over a four-year period, rising to 817 in 2017 from 430...