This study shows some important features about very elderly hospitalized patients in Spain. There is a wide gap between the number of men and women in the analyzed population, with men accounting for just over a third of the very old inpatients. The reasons for this imbalance probably reside in the differential life expectancy between genders and the subsequent smaller proportion of men among very elderly inhabitants in Spain, as in fact men had a higher probability of being admitted to hospital than women. This result agrees with other recent studies that show differences in hospitalization patterns depending on gender in elderly patients: women admitted in Spanish hospitals tend to be older and with lower Charlson index scores than men (5).
Previous studies analyzing trends in hospitalized patients have focused on specific diseases (9, 10) or single centers, limiting the size of the population analyzed (11, 12). To our knowledge, this is the first study to analyze the general trends in very elderly hospitalized patients in Spain, although the Spanish Ministry of Health does periodically provide a summary of the information contained in the MBDS. In 2012, they analyzed the characteristics of hospitalized patients aged over 65; as in our study, their results showed an increase in that population group, combined with a decrease in the mean length of stay, comparable to what we observed in the very elderly population (13). We also found that the number of very old hospitalized patients increased faster in the oldest age segments, with the most rapid increase in people aged 95 and older.
Regarding the causes of hospitalization, there is some overlap between our data and the summary from the Spanish Ministry of Health: diseases of the circulatory and respiratory systems; neoplasms; and diseases of the muscular, skeletal and genitourinary apparatus were among the most frequent diagnoses. However, wounds and poisoning was the fifth most frequent chapter in the Ministry report, while this category did not even rank among the top 10 diagnoses at discharge in our study. This difference could be explained because people tend to cut down on their activity levels as they age, so very elderly people carry a lower risk of wounds or poisoning. Other differences reside in the chapters related to symptoms, signs and poorly defined states as well as endocrine, nutritional, and metabolic diseases, which were among the most frequent diagnoses in the Ministry summary but were much less prominent in our study population.
In 2008, the US Agency for Healthcare Research and Quality (AHRQ) published a statistical brief that presented data from the Healthcare Cost and Utilization Project (14). Authors described patient characteristics and hospital utilization among the oldest adults, including those aged 85 years and older. Diagnoses were quite similar to those in our cohort, with heart failure, pneumonia, urinary tract infection, hip fracture, stroke and chronic obstructive pulmonary disease (COPD) among the 10 most frequent diagnoses. However, blood infection (septicemia), kidney failure, and electrolyte and water misbalances were also top diagnoses in the USA, unlike in Spain. Variations in coding practices between countries could explain some of this difference.
The MBDS data show a downward trend in the relative incidence of some of the most frequent diagnoses in Spanish hospitals, including femoral neck fractures, COPD, ischemic encephalopathy and ischemic cardiomyopathy. These disease categories share a strong correlation with vitamin D deficiency, osteoporosis, hypertension, diabetes, obesity, and dyslipidemia—all risk factors that public health policies have been addressing in the last decades. Our data are suggestive of the effectiveness of such policies.
Hospitalization costs changed significantly during the study period. The pronounced increase from 2000 to 2007 was attenuated in 2008–2011 before dropping in 2012–2015. This reversal could be due to the health budget adjustment in Spain following the 2008 economic crisis. Mean length of stay gradually decreased between 2000 and 2015 in all age segments, coinciding with efforts from within the Spanish healthcare system to improve the efficiency of hospital care.
Similarly to our study, the AHRQ data show that very elderly people made up 8% of inpatients in 2008. Although they showed a lower mean length of stay (5.6 days in the USA versus 9.19 days in Spain), the total cost of the hospital stay was higher (USD 9400 versus EUR 5212, respectively). These figures are in accordance with the different healthcare financing systems between the two countries, with private hospital providers dominating in the USA, in contrast to the public hospitals that provide most care in Spain.
To our knowledge, few studies have focused on mortality in the very elderly. In addition, the diversity of the patient populations, reasons for hospitalization, ages at discharge, and lengths of hospital stay make comparisons difficult. The rate of in-hospital mortality has been estimated at 8.2% in those older than 65 (15), compared to 13.3% in patients older than 90 (16). An Italian study published in 2003 analyzed in-hospital mortality in the very elderly in a cohort of 987 patients. They observed a 16.2% mortality rate in their population, which is slightly higher than the 14.64–13.83% seen in our study.
In addition, with regard to the mortality rate among very elderly inpatients, our data show a downward trend in those aged 85–89 years, stability in the group aged 90–94 years, and an upward trend in individuals aged 95 or older. These results could be explained by the progressive medicalization of advanced age and death, which is more frequent in urban areas (demographic trends in Spain show an increasing concentration around large cities). This pattern is in accordance with previous data published in Spain (14) showing that deaths occur more frequently in a hospital setting in cities and that this tendency is becoming more pronounced with time.
The strengths of our findings lie in the large sample size, the 15-year follow-up period, and the reliability of the data, which come from a well-established administrative system. However, our study has some limitations that should be considered when interpreting its results. The source of our data is the MBDS, an administrative database that includes data collected from each discharge report in Spain. This kind of database is of good quality for administrative data, but it shows low sensitivity and high specificity for clinical data such as main diagnoses (17, 18). Another limitation is the anonymity of the database (patients are not identified by clinical history number or name), which prevents any analysis of readmissions; moreover, patients who were transferred from one hospital to another would have duplicate entries.
In the clinical field, the database is limited because it uses ICD-9-CM diagnostic codes to identify the main cause of hospitalization. The major concern in this case is the questionable accuracy of these diagnoses, which cannot be verified.
Despite these limitations, the MBDS discharge data is a mandatory register with an estimated coverage of 98% (19). Data are also audited periodically, minimizing inaccuracies. Finally, the Spanish health system provides universal healthcare coverage, allowing the standardization of data from patients with different socioeconomic backgrounds or living in different Spanish regions.