INTRODUCTION

Previous studies have shown that the in-hospital mortality rate in older adults is approximately 12 to 14%, which is two to three times higher than mortality in people under 60 years of age; the most important causes of death being pneumonia, stroke, myocardial infarction, diabetes and cancer ¹. Different studies carried out in developed countries have shown that advanced age, poor functional and cognitive status, delirium, malnutrition, multiple comorbidities, frailty and severity of illness are factors independently associated with a higher risk of mortality and prolonged hospital stay ^{2 , 3}.

The Comprehensive Geriatric Assessment (CGA) is a multidimensional and interdisciplinary diagnostic tool that identifies and quantifies the physical, functional, psychological and social problems that older adults may present ⁴. Because of its diagnostic accuracy, the CGA has proven to be considerably useful in defining the type of care required by older adult patients with comorbidities, functional dependence and frailty. Its application in hospitalized patients has been proposed in order to reduce some adverse outcomes, such as mortality, prolonged hospital stay, functional deterioration, nosocomial infections, re-admissions and institutionalization ^{5 , 6}.

Due to the lack of Peruvian studies on the subject, the aim of this study was to determine the factors associated with mortality in older adults admitted to an internal medicine department of a Peruvian hospital. For this purpose, we collected data from the medical records, including the components of CGA. The study will serve to design intervention strategies aimed at addressing the associated risk factors and to improve the quality of care for the older adult population, considered a vulnerable segment and generally at social risk.

THE STUDY

FINDINGS

A total of 360 patients were evaluated (median age 76 years, IQR: 67-83). Of the total, 54.2% were male; 57.8% had a stable partner (married or cohabiting); and 71.4% were illiterate or had primary education. Regarding clinical data, 7.2% were polymedicated patients, 53.1% were hospitalized, and 34.2% had a history of falls in the last year. The CGA showed that 44.4% had urinary incontinence, 15.8% had pressure ulcers, 50.6% had high comorbidity, 54.7% had total functional dependence, 60.8% had malnutrition, 47.5% had social problems and 38.6% had delirium at admission. Of a total of 238 patients evaluated who did not have delirium on admission or whose symptoms subsided during hospitalization, 33.2% had cognitive impairment and 12.2% depression (Table 1).

The median length of hospital stay was 9 days (IQR: 6-13). The most frequent diagnoses on admission were pneumonia in 15.8% and stroke in 14.4% (Table 2) of the patients. Of 360 patients studied, 45 died during their hospital stay, with a cumulative incidence of mortality of 12.5%. The main causes of death were sepsis (44.4%), multiorgan failure (35.6%), in-hospital pneumonia (8.9%) and acute renal failure (4.4%).

Compared to non-deceased patients, deceased patients had a higher frequency of: anemia (46.7% vs. 31.4%, p = 0.043), hypoalbuminemia (88.9% vs. 69.2%, p = 0.006), pressure ulcers (31.3% vs. 13.7%, p = 0.003), high comorbidity (75.6% vs. 47.0%, p < 0.001), functional dependency at admission (93.3% vs. 49.2%, p < 0.001), malnutrition (84.4% vs. 57.5%, p = 0.002) and delirium (80.0% vs. 32.7%, p < 0.001) (Table 3).

We calculated adjusted associations using a multiple Poisson regression model with robust variance in the variables associated with the outcome of interest in the bivariate model. In the multivariate model, delirium was associated with a 3.64-fold increase in the risk of in-hospital mortality (RR = 3.64; 95% CI: 1.51-8.76, p = 0.004) (Table 4).

DISCUSSION

Delirium is characterized by an abrupt change in mental status, with altered attention and cognition, frequently accompanied by a disorder of consciousness, disorientation and inversion of the sleep-wake cycle ¹⁴. This geriatric syndrome increases the risk of mortality, prolongs hospital stay, produces functional deterioration and institutionalization in older adults, which increases health care costs ¹⁵.

In our research, 38.6% of the patients had delirium at the time of admission and its presence was associated with an increased risk of death. Studies conducted in national hospitals have shown that 34.9 to 42.7% of older adults admitted to emergency services for medical conditions present delirium, which usually coexists with conditions of functional dependence, chronic cognitive impairment and dehydration ¹⁶. Despite its high frequency, delirium is often not correctly diagnosed and, consequently, its treatment is not accurate, and it can be confused with dementia, depression or with the changes produced by aging ¹⁴. According to the latter, only 27 (7.5%) of our patients had a diagnosis of delirium registered in their medical record.

Previous studies have shown an association between delirium and a high risk of death, independent of the effect of other factors, such as advanced age, cognitive impairment, comorbidity, functional status and severity of illness ^{14 , 15}. In a study of 469 patients over 70 years of age belonging to Project Recovery, a controlled clinical trial for the prevention of delirium, Dharmarajan et al. ¹⁷ found that 15% of patients developed delirium during hospitalization. Those affected had a higher frequency of falls, pressure ulcers; as well as use of mechanical restraint and complications during evolution, such as sleep disorders, malnutrition, dehydration and pneumonia. It has been proposed that the increased risk of death in delirious patients could be mediated by this cascade of adverse events.

Our study found a higher frequency of hypoalbuminemia, anemia, pressure ulcers, high comorbidity, functional dependence on admission, and malnutrition among the deceased patients. These factors have been associated in the international literature with a higher risk of death in hospitalized older adults, but did not reach statistical significance in the multivariate model of this study.

Akirov et al. ¹⁸ evaluated a cohort of 30,732 patients (mean age 67 years) and found an in-hospital mortality rate of 67% in patients with mild hypoalbuminemia (2.5-3.5 g/dL) and 83% in those with severe hypoalbuminemia (<2.5 g/dL). The association was present in all age groups, and significantly normalizing the albumin levels reduced the risk of death. Specifically, in older adults, an association has been found between hypoalbuminemia and an increased risk of death, prolonged hospital stay, and re-admission after discharge ^{5 , 6}.

In a study of 17,030 older adults from Calgary (Canada), an increased risk of hospitalization and death was found among patients with anemia. The observed association was independent of age, sex, renal function, comorbidity or history of diabetes in the patients studied ¹⁹.

In older adults with pressure ulcers at the time of hospital admission, a shorter survival time has also been described when compared to patients without ulcers (94 vs. 414 days, p = 0.005), especially in patients with dementia, anemia or malnutrition ²⁰.

De Gelder et al. ^{3 )} designed a predictive model of 90-day mortality after hospital admission in older adults. Six variables were included in the model: assessment of comorbidity by CCI, platelet count, oxygen saturation, CRP values, urea and plasma glucose. Of the total of 517 patients, 18.2% died during the observation period, which corresponds to a mortality of 53% in patients located in the highest risk decile.

On the other hand, the association between poor functional status on admission and high mortality in older adults is well known. Incalzi et al. ², in their study of 308 older adults admitted to a hospital ward, reported an excess of death among patients with functional dependence determined with the Katz index. Possible explanations for this association have been proposed, such as a greater vulnerability of patients with functional dependence and a high frequency of comorbidity, immobility, cognitive impairment, depression, polypharmacy, social problems and malnutrition in these patients.

A higher mortality rate has been described in malnourished older adults. Avelino-Silva et al. ⁶ prospectively evaluated a group of 746 older adults admitted to the geriatrics service of a university hospital in Brazil. In their study, patients with a low MNA-SF score who had hypoalbuminemia were twice as likely to die as patients without this condition.

Our study has several limitations. First, since it considers patients from the third level of healthcare, its conclusions cannot be generalized to other realities, as this would compromise its external validity. Second, a larger sample size could have improved the statistical power of the research. Third, we mainly focused on the evaluation of geriatric factors associated with higher in-hospital mortality rather than on the severity of the disease at admission. Fourth, we did not consider the frailty syndrome, which may have been present in a significant group of patients.

In conclusion, in older adult patients admitted to an internal medicine service, delirium on admission was independently associated with a 3.64-fold increase in the risk of in-hospital death.