title: Incidence of adverse events and negligence in hospitalized patients. Results of the Harvard Medical Practice Study I.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  Adverse events occurred in 3.7 percent of the hospitalizations (95 percent confidence interval, 3.2 to 4.2), and 27.6 percent of the adverse events were due to negligence (95 percent confidence interval, 22.5 to 32.6). Although 70.5 percent of the adverse events gave rise to disability lasting less than six months, 2.6 percent caused permanently disabling injuries and 13.6 percent led to death. The percentage of adverse events attributable to negligence increased in the categories of more severe injuries (Wald test chi 2 = 21.04, P less than 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 less than 0.0001). The percentage of adverse events due to negligence was markedly higher among the elderly (P less than 0.01). There were significant differences in rates of adverse events among categories of clinical specialties (P less than 0.0001), but no differences in the percentage due to negligence.
  
  
  CONCLUSIONS
  There is a substantial amount of injury to patients from medical management, and many injuries are the result of substandard care.
authors.affiliation: Division of General Medicine, Brigham and Women's Hospital, Boston, MA 02115.
authors.forename: T A
authors.initials: TA
authors.lastname: Brennan
authors.forename: L L
authors.initials: LL
authors.lastname: Leape
authors.forename: N M
authors.initials: NM
authors.lastname: Laird
authors.forename: L
authors.initials: L
authors.lastname: Hebert
authors.forename: A R
authors.initials: AR
authors.lastname: Localio
authors.forename: A G
authors.initials: AG
authors.lastname: Lawthers
authors.forename: J P
authors.initials: JP
authors.lastname: Newhouse
authors.forename: P C
authors.initials: PC
authors.lastname: Weiler
authors.forename: H H
authors.initials: HH
authors.lastname: Hiatt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004185:Disability Evaluation; D006753:Hospital Records; D006761:Hospitals / Q000592:standards / Q000706:statistics & numerical data*; D006801:Humans; D007049:Iatrogenic Disease / Q000453:epidemiology*; D007223:Infant; D007231:Infant, Newborn; D007297:Inpatients / Q000706:statistics & numerical data*; D008318:Malpractice / Q000706:statistics & numerical data*; D008875:Middle Aged; D009017:Morbidity; D009518:New York / Q000453:epidemiology; D011897:Random Allocation; D012494:Sampling Studies