Results
General Features and Quality Assessment
Details of the methodological characteristics of the nine studies that were included in the review are summarized in Table 1. Seven studies were carried out in the USA, one in the UK and one in Canada. There appears to be a relative dearth of recent work in this area—four studies were carried out in the 1980s, two in the 1990s and only three since the year 2000. Two are re-analyses of data from large adverse event studies of all ages described earlier. Sample sizes varied according to the methods used—smaller studies (such as Foreman et al.) tended to involve prospective clinical assessment of patients, with larger studies employing retrospective case record review (as in Thomas and Brennan and Sari et al.) or analysis of central administrative electronic databases. All studies used arbitrary definitions of 'elderly', with only one study stating that the age limit used was based on pilot work for those at most risk.
When subjected to the modified MINORS score described above, the studies exhibited a wide variation in study quality ranging from 0.52 to 0.81 (maximum score 1.00), with a mean score of 0.69. Full scoring is provided in Supplementary material, Appendix 2.
Definitions and Methodologies Used
The studies each had different aims and, therefore, provide data on a wide range of aspects of adverse events in older people. The principal aim of six studies was to examine adverse events in older people—in one study to assess the effect of an intervention, in another to look at the effect of patient factors on outcomes of adverse events, rather than their effect on adverse events alone, and in another to assess the impact of a suspected underlying cause. Four of the studies allowed comparison between older and younger patient groups, while the remainder solely examined adverse events in older inpatient groups.
Definitions of health care-associated harm vary hugely between the studies, clearly influencing the type of data generated. Some studies employed definitions similar to those used widely in the large international adverse event studies of all ages, while others sought to identify adverse events specifically occurring in older people, such as those encompassed by the phrase 'symptoms of depressed psychophysiologic functioning' in Gillick et al. (confusion, not eating, falls, incontinence). Foreman et al. also looked only for geriatric syndromes: acute confusion, pressure ulcers, nutritional problems, adverse drug reactions, falls, transient urinary incontinence. Ackroyd-Stolarz et al. also acknowledged the need to focus on issues particularly relevant to older people and created 'geriatric-specific screening criteria for adverse events', as well as looking for more generic adverse events such as procedure-related complications.
All studies used similar subject recruitment and selection processes, usually using consecutive admissions to the hospitals in question. Some investigators attempted to sample the more dependent patients (such as Lefevre et al., who excluded elective surgical patients and those with a short length of stay), while others employed exclusion criteria which may have meant that the frailest patients were not studied (such as Ackroyd-Stolarz et al., who excluded patients with previous hospitalizations in the last 6 months in order to gain a sample more representative of community-dwelling older people).
All studies used some form of case record review or review of administrative data to aid the detection of adverse events, which brings with it its own problems such as hindsight and observation bias. Some supplemented this with patient or staff interviews, or other data collected on a hospital or state level. It is interesting to note that Becker was the only investigator to use official adverse event reporting systems to detect adverse events; perhaps this reflects a perception of the reliability of existing reporting systems in identifying adverse events.
Table 2 shows a summary of the findings of the nine studies identified by this review in terms of the incidence, types, causes, preventability and outcomes of adverse events in older people.
Incidence of Adverse Events A wide variation in the incidence of adverse events in older people was reported in these studies. The two studies that had been part of large international adverse events studies, in which data were re-analysed to look at the differences between the old and the young, showed the lowest adverse event rates: 5.29% and 6.2%. In contrast, studies that had been carried out specifically to look at adverse events in older people found a much higher incidence such as in the study conducted by Lefevre et al., in which there were more adverse events than patients overall, with 1.8 adverse events per patient, and Foreman et al., who reported an incidence of 60%. This huge variation reflects the different methodologies employed, particularly in terms of the different definitions of adverse events used and the fact that investigators who were particularly focusing on older people tended to seek out information about conditions such as delirium or incontinence not included in the large adverse event studies which were not designed with older people in mind.
Two studies confirmed the relationship between age and adverse event incidence reported by the large adverse international studies. Jahnigen et al. found that age seemed to be related to the incidence of adverse events independently of disease severity or length of stay and Sari et al. found that each year of life increased the risk of an adverse event by 28%, after adjustment for length of stay.
Types and Preventability of Adverse Events
A wide range of types of adverse events were reported in these studies, which again varied according to the study's definition of adverse events. These ranged from geriatric syndromes such as falls, delirium, pressure sores and incontinence to more 'conventional' adverse events such as adverse drug events, hospital-acquired infections and procedure-related complications in the other studies. A summary of the wide range of adverse events that affect older people is given in Table 3, together with the likelihood that they would have been detected using traditional retrospective case record review approaches.
Lefevre et al. found that 52.1% of the iatrogenic complications experienced by older people were deemed to be preventable, and Thomas and Brennan found a significantly increased incidence of preventable adverse events in older people than younger, whereas Sari et al. did not, after adjustment for other confounders.
Factors Other Than Age Affecting the Incidence of Adverse Events
Becker and Lefevre et al. showed that loss of functional ability was independently associated with adverse events, while Thomas and Brennan reported that clinical complexity probably accounted for the observed association with age, rather than simply age discrimination or age alone.
The factors other than age which were associated with a statistically significant increased risk of adverse events in these studies were
functional loss: the inability to perform at least one activity of daily living on admission, living in a nursing home;
comorbidity and severity of illness: severity of illness on admission, reduced level of consciousness on admission diagnosis-related group (DRG) complexity, having the admitting diagnosis 'infection';
demographic factors: being of Afro-American ethnicity, being male;
receiving less than adequate quality of care (as judged using the RAND scale);
having a prolonged length of stay in the emergency department.
The only factor in all the studies which was found to be associated with significantly fewer adverse events was good documentation of functional status during the admission; this halved the risk of adverse event occurrence in this study.
Outcomes of Adverse Events
Jahnigen et al.'s study was the only one to describe the effect of adverse events on patient experience, stating that all adverse events were likely to have an effect, ranging from discomfort to death. Both Jahnigen et al. and Ackroyd-Stolarz et al. found that patients with adverse events were likely to be in hospital twice as long as those without.
Only Jahnigen et al. and Gillick et al. investigated the incidence and deleterious effects of interventions employed when adverse events occurred. Jahnigen et al. found that restraint and/or tranquilization were 'often necessary' in patients who developed delirium, with subsequent risks of pressure sores, aspiration and self-injury. Gillick et al. found that psychotropic drugs and restraints used for delirium, nasogastric tubes inserted for feeding in undernourished patients and catheters inserted for incontinence were more likely to be used in older people than younger patients. This in turn led to complications such as urinary tract infections, septic shock and fractures in older people, with none occurring in the younger patients who received these interventions. The authors acknowledge that this was a very small sample, but based on evidence in the literature at the time, gave a suggested risk of complications from treatment given as a result of adverse events of 1.0% for young patients, and 5.7% for elderly patients (P < 0.0001).
Several of the studies described the proportions of patients who died during the study period, but only Thomas and Brennan related this to adverse event occurrence; however, there was no significant difference between the rates of death considered to be attributable to adverse events in younger compared with older patients. Only Davis et al. investigated whether there was a link between adverse event occurrence and the need for nursing home placement on discharge from hospital; in this study, most adverse events were minor and transient and their occurrence did not correlate with either nursing home placement or change in level of care on discharge.