The main findings of this study were the following: patients aged ≥ 80 years represented a significant portion of patients admitted to the ICU; had significant comorbid conditions; were admitted mainly because of acute dysfunction of the cardiac and respiratory systems; and compared with the younger groups, received similar life sustaining treatments but were more likely to have Do-Not-Resuscitate orders and to die in the hospital than the younger groups.
The age structure of the world population has shifted and will continue to do so with the proportion of old people increasing in both developed and developing countries . In parallel with this shift, more old patients are admitted to ICU. In Australia and New Zealand, the proportion of patients aged > 80 years was 13% of the adult ICU population and increased by 5.6% between 2000 and 2005 . In Denmark, a study of 49,938 ICU admissions found that the proportion of patients aged ≥ 80 years increased from 11.7% of all ICU patients in 2005 to 13.8% in 2011 . In the current study, patients aged ≥ 80 years constituted 7.9% of all patients admitted to the ICU between 1999 and 2011 and 12.8% of patients ≥ 50 year-old, with the proportion of admissions generally showing random variation from year to year. These findings are different than other studies [16, 17] likely because the Saudi population is much younger than those of developed countries. In 2011, people aged ≥ 80 years represented 0.6% of the population compared with 3.8% in Australia, 4.2% in Denmark and 3.8% in the United States .
Physicians frequently consider old age when deciding on the provision of life-sustaining measures. An observational simulation study found that 86, 78 and 62% of participating physicians (predominantly males without religious beliefs; median ICU experience = 9 years) felt that noninvasive mechanical ventilation, invasive mechanical ventilation or renal replacement therapy was warranted, respectively for patients aged ≥ 80 years . On multivariate analysis, age < 85 years, self-sufficiency and bed availability were associated with ICU admission . In a systematic review of 10 observational studies of seriously ill patients considered for ICU admission during periods of reduced bed availability, Sinuff et al. found that age and severity of illness were most strongly associated with a refusal to admit to the ICU . A recent prospective study of patients > 85 years presenting to the emergency departments of 15 Parisian hospitals found significant variability in ICU admission even after adjustment for patients’ characteristics . The geographic variation in ICU use for patients ≥ 85 years old was also seen in another study where it was less common in England (1.3%) than the United States (11.0%) . In the current study, we have observed that patients aged ≥ 80 years were frequently provided with life support measures, such as mechanical ventilation and renal replacement therapy, like younger patients. However, age ≥ 80 years was found to be an independent risk factor for the practice of Do-Not-Resuscitate orders after controlling for co-morbid conditions.
Low physiological reserve and comorbidities often place very old people in a situation of greater complexity, which may impact outcome. However, it is thought that they have lived to that age because they are resilient to acute illnesses. Studies generally show higher critical illness-associated mortality in the old and very old patients. A study that classified patients into 75–79, 80–84 and ≥ 85 year age groups found that age was not associated with ICU mortality, but with long-term mortality (aOR: 2.17, for patients ≥ 85 years old and 1.82, for patients 80–84 years old) . Another study found that patients aged 75–84 and ≥ 85 year-old had aORs of 1.38 (95% CI, 1.19-1.59) and 1.53 (95% CI, 1.29-1.81), respectively for 28-day mortality as compared with the 65–74 year-age group . A secondary analysis of data from a randomized trial comparing the effects of dopamine and norepinephrine in patients with shock found that the mortality rates were higher in the old (75–84 years) and very old (≥ 85 years) patients at 28 days, at hospital discharge, and after 6 and 12 months . Most very old patients were dead at 6 (92%) and 12 months (97%) with mortality rates increasing with age in all types of shock . A retrospective Norwegian cohort study (n = 27,921) found that the hospital mortality was 21.4% in patients aged 50–79.9 years and 32.4% in patients aged > 80 years, who also received less mechanical ventilation (40.6% versus 56.1%) and had shorter median ventilatory support time (0.8 days versus 1.9 days) . The mortality of the very elderly patients may be affected by admission type. A retrospective cohort study that the 30-day mortality of elderly patients (≥ 80 years) was 43.7% in medical, 39.6% in acute surgical, and 11.6% in elective surgical ICU patients with a corresponding adjusted 30-day mortality rate ratios compared with the 50–64 year-old patients were 2.7 (95% CI, 2.5-3.0) in medical, 2.7 (95% CI, 2.4-3.0) in acute surgical and 5.2 (95% CI, 4.1-6.6) in elective surgical ICU patients . The adjusted mortality rate ratios for 31-365-day mortality among elderly patients were 2.5 (95% CI, 2.1-2.9) for medical, 2.2 (95% CI 1.9-2.5) for acute surgical and 1.9 (95% CI, 1.6-2.3) for elective surgical ICU patients . A study that used Project IMPACT data for 124,885 patients treated from 2001 to 2004 found that mortality rates approximately doubled in the elective surgical group among patients aged in their 70s (2.4%), 80s (4.3%), and 90s (9.2%) but rose less dramatically in the medical group (27.0%, 30.7%, and 36.0%, respectively) . Old age (> 65 years) has been associated with increased community-acquired pneumonia mortality  and ARDS mortality (OR per additional 10 year, 1.27; 95% CI, 1.07-1.50) . In the current study, the ICU mortality was similar in the three age groups, but the hospital mortality was significantly higher in patients aged ≥ 80 years having a higher adjusted mortality risk compared to younger age groups (50–64.9 and 65–79.9 years). This was observed in different admission types, except for admissions due to neurologic disease and hospital-acquired pneumonia. This could be because patients aged ≥ 80 years had high prevalence of chronic illnesses and functional disability in our study.
The findings of this study should be interpreted in the light of its strengths and limitations. Strengths include the large sample size. Limitations include being a monocenter study and lack of data on post-ICU care processes, which may have affected hospital outcome, and on long-term outcomes such as cognitive function and disability. Critical illness in old people has been associated with decline in cognitive function. Analysis of data from a prospective cohort study of 2929 individuals ≥ 65 year-old without dementia showed that adjusted hazard ratio for incident dementia was 1.4 following a noncritical illness hospitalization (95% CI, 1.1-1.7; p = 0.001) and 2.3 following a critical illness hospitalization (95% CI, 0.9-5.7; p = 0.09) . This may be one of the reasons for increased mortality after ICU discharge.