Incidence of adverse events and negligence in hospitalized
patients: results of the Harvard Medical Practice Study I
The following is an overview of the study. For the entire study, click here to download the PDF.
As part of an interdisciplinary study of medical injury and malpractice litigation, we
estimated the incidence of adverse events, defined as injuries caused by medical management, and of the
subgroup of such injuries that resulted from negligent or substandard care.
We reviewed 30 121 randomly selected records from 51 randomly selected acute care, nonpsychiatric
hospitals in New York State in 1984. We then developed population estimates of injuries and
computed rates according to the age and sex of the patients as well as the specialties of the physicians.
Adverse events occurred in 3.7% of the hospitalizations (95% confidence interval 3.2 to 4.2), and
27.6% of the adverse events were due to negligence (95% confidence interval 22.5 to 32.6). Although
70.5% of the adverse events gave rise to disability lasting less than 6 months, 2.6% caused permanently
disabling injuries and 13.6% led to death. The percentage of adverse events attributable to negligence
increased in the categories of more severe injuries (Wald test x2 = 21.04, p,0.0001). Using weighted
totals we estimated that among the 2 671 863 patients discharged from New York hospitals in 1984 there
were 98 609 adverse events and 27 179 adverse events involving negligence. Rates of adverse events
rose with age (p,0.0001). The percentage of adverse events due to negligence was markedly higher
among the elderly (p,0.01). There were significant differences in rates of adverse events among
categories of clinical specialties (p,0.0001), but no differences in the percentage due to negligence.
There is a substantial amount of injury to patients from medical management, and many
injuries are the result of substandard care.