A study of Long Island's 52 for-profit nursing homes has concluded that the homes are understaffed, even as their owners have enjoyed increasing profits and generous salaries in recent years.

The study, conducted by Labor Research Association of Manhattan and sponsored by two local health care workers' unions - one of which is in contract negotiations - is based on financial reports filed by the homes for 1993 through 1997.

Residents of for-profit nursing homes receive an average of 2.6 hours of nursing care per day, the report concludes, less than the state average of 2.9 hours, and less than the 3.7 to 4.7 hours of care per day that advocates and experts recommend.