This study evaluated the characteristics and outcomes of the largest cohort of nonagenarians in ICU published to date and provided data on their long-term survival.
Despite the fact that elderly patients are increasingly been treated in the intensive care environment, there is a lack of information available about their prognosis and outcome.
The 81.7 % ICU-, 70 % hospital-, and 35 % one-year survival rates stand in contrast to and challenge widespread beliefs about the poor short- and long-term prognosis of nonagenarians admitted to the ICU. Especially the hospital mortality rates of patients undergoing planned surgery were remarkably low, whereas the outcome worsened after unplanned ICU admission and especially after ICU readmission. Within the group of nonagenarians, creatinine, bilirubin, age, and necessity of catecholamine therapy cause of admission were independent factors for 28-day outcome. Not surprisingly, the 18.3 % ICU mortality of the study group of very elderly ICU patients was higher than that of the departments overall ICU mortality of 9 %. This age-related mortality risk is in line with many other outcome studies on a wide variety of critically ill ICU populations. Whereas several studies have identified age as an independent risk factor for ICU mortality [6, 7, 12–16], other studies have found the severity of illness and comorbidities to be more important risk factors than age itself [5, 17–20].
Analyzing data from a large Austrian database (n = 17,126), Ihra et al. found a significantly higher hospital mortality rate in patients older than 80 years in comparison to patients younger than 80 years (31.0 vs. 15.9 %) . Only few observational studies have analyzed the outcome of the nonagenarians (≥90 years). Demoule et al. examined 36 patients ≥90 years in a French ICU. ICU and hospital mortality were 28 and 47 %, respectively . Rellos et al. analyzed 60 patients ≥90 years in a Greek ICU, which accounted for 1.1 % of all ICU admissions. The average length of stay in ICU and hospital was 5 and 23 days, respectively, with an ICU mortality of 20 % . Other studies with data of patients >85 years demonstrated ICU mortality rates ranging from 14.6  to 36.6 % .
The comparability between all these studies is limited by differences in the study settings and health care systems resulting in different ICU admission policies and practices. Additionally, some studies analyzed predominantly elderly patients with unplanned ICU admissions , explaining differences in mortality rates between studies. In contrast, the present study included all very elderly patients treated in the ICU. One possible contributing reason for a higher mortality rate in elderly ICU patients is the fact that the decision to limit or withhold therapy occurs more frequently among elderly ICU patients. Accordingly, Seder et al. found increasing rates of withholding and withdrawal of life support in the ICU with advanced age , and Al-Dorzi et al. observed a more frequent application of Do Not Resuscitate- orders in patients >80 years . In line with these previous findings, we recorded a quarter of very elderly ICU patients not receiving maximal therapy on the basis of an advanced directive and/or a presumed poor prognosis.
Patients admitted to the ICU following scheduled surgery had lower mortality rates than patients with unscheduled admission. Correspondingly, other studies observed the best outcome in the scheduled surgery group among very elderly patients [22, 25]. Additionally, admission for unplanned surgery was a predictor for poor outcome . The differences in mortality between the three subgroups can be partly explained by the severity of acute illness. Accordingly, we observed the highest mortality rates in patients following medical admission.
At present, the average life expectancy of a 90-year-old German person is 3.8 years for men and 4.3 years for woman, and life expectancy at an age of 95 years still is 2.7 to 3 years . Approximately, one-third of our entire study population was still alive at 1 year after ICU discharge. Similar findings were made by recent studies with one-year survival rates among elderly ICU patients ranging from 28 to 56 % [25, 27–30].
Limited ICU resources are one of the main reasons for controversial discussions about the accessibility of intensive care treatment for elderly patients . However, findings of the recently published ELDICUS study suggest that of all patients, elderly subjects have a high benefit from ICU treatment .
Our study cohort represented only 1.1 % of all departmental ICU admissions from 2008 to 2013. However, the proportion of elderly patients is expected to constantly rise as a result of the demographic transition and this will also affect intensive care medicine [5, 11]. Thus, intensivists will increasingly have to cope with the special challenges of an increasingly aging ICU population and related aspects, such as multimorbidity, polypharmacy, and ethical questions. Our patients were hospitalized mainly for traumatic causes and cardiovascular diseases. Corresponding findings were made by prior studies [5–7, 11], especially the incidence of cardiovascular diseases particularly increases with advanced age .
The results of our study have to be interpreted with caution due to the following limitations: Because of the single-center study design, results may not be generalizable to other settings. The relatively good survival rates of our nonagenarian ICU patients may have been the result of a preselection bias of restrictions to ICU admission decisions in this age group. This important aspect was outside the scope of this study. Furthermore, our follow-up data do not provide insights into quality of life and functional status after hospital discharge. Other study groups found, that both, quality of life and autonomy in activities of daily living among elderly ICU survivors were deemed to be satisfactory [28, 32]. Further and larger multicenter studies on the long-term outcome of elderly ICU patients with regard to survival and quality of life are warranted.