1. Introduction
Despite recent advancements in the treatments for heart failure (HF), HF remains one of the major causes of increased risks of hospitalization and mortality [
1]. In Japan, the prevalence of HF is increasing [
2] in association with an increasing elderly population [
3]. Multiple comorbidities are a well-known condition in the elderly population [
4] and are generally associated with a greater risk of death and longer length of hospital stay. Certainly, in Japan, hospitalized patients with acute decompensated HF have multiple comorbidities [
5,
6,
7]; an in-hospital mortality rate of approximately 5%, which remains substantial; and a median length of hospital stay of 14–21 days [
5], which is substantially longer than that in any Western and Asian countries in association with a different socialized medical system in Japan [
8]. HF with preserved ejection fraction (EF) (HFpEF) is prevalent in elderly HF patients and remains a major concern considering its limited treatment options [
9]. Thus, it is important to identify the comorbid conditions or factors on admission that are associated with an increased risk of in-hospital mortality and longer length of hospital stay in patients hospitalized due to acute decompensated HF, specifically patients with HFpEF.
Malnutrition is frequently observed and an important risk factor of poor outcomes in patients with HF [
10]. Although no nutritional evaluation method for patients with HF has yet been established, it has been reported that the Geriatric Nutritional Risk Index (GNRI) is useful for predicting the mortality risk of elderly HF patients [
11]. The GNRI is a simple and objective nutritional index that uses the ideal body weight ratio and serum albumin, and GNRI < 92 is generally used for evaluating the risk of morbidity and mortality in hospitalized elderly patients [
12]. However, the impact of the GNRI on short-term outcomes such as in-hospital mortality and LOHS remain uncertain. In particular, the effects of GNRI on such clinical outcomes in patients with HFpEF, which is assessed separately with HF with reduced EF (HFrEF), are of significant interest.
This study aimed to identify the factors associated with increased in-hospital mortality and longer length of hospital stay by considering the GNRI on admission in acute decompensated HF patients with HFrEF and HFpEF, respectively.
4. Discussion
In this study, several important findings were reported that provide insight into the association between nutritional status on admission and short-term outcomes in hospitalized patients with acute decompensated HF, specifically patients with HFpEF. First, in HFrEF, although serum sodium and hemoglobin levels were identified as independent factors associated with increased in-hospital mortality, there was no association between malnutrition expressed as GNRI < 92 and in-hospital mortality. Second, only serum sodium level was the independent factor associated with longer length of hospital stay, and no association was observed between malnutrition expressed as GNRI < 92 and length of hospital stay in patients with HFrEF. Third, in HFpEF, patients with history of prior HF hospitalization and patients with lower eGFR levels were likely to experience in-hospital mortality, but malnutrition expressed as GNRI < 92 was not a factor associated with increased in-hospital mortality. Finally, in HFpEF, GNRI < 92 was significantly associated with longer length of hospital stay and lower hemoglobin, higher BNP, and elevated CRP levels among patients hospitalized due to acute decompensated HF. Our findings suggest that nutritional status on admission assessed using the GNRI may be an important factor when stratifying patients at high risk for longer length of hospital stay in patients hospitalized due to acute decompensated HF, and this should be emphasized in patients with HFpEF.
Previous studies have reported that body mass index and serum albumin levels, which are traditional indicators of nutritional status, can predict mortality in patients with HF [
17,
18,
19]. Additionally, more recently, some other indices that were basically computed by serum albumin level and lymphocyte count, such as the Prognostic Nutritional Index (PNI) and Controlling Nutritional Status (CONUT) score, have also been shown to have prognostic value in patients with HF, and more precisely assessed the prognostic values of malnutrition on long-term clinical outcomes in patients with HF [
20,
21]. These studies suggest that assessment of nutritional status is important in patients with stable HF. Additionally, a previous study has reported that in patients hospitalized due to acute decompensated HF, either a severe CONUT score or low PNI was associated with an increased risk of in-hospital mortality and prolonged length of hospital stay [
22]. Thus, rapid assessment of nutritional status on admission is also important in patients hospitalized due to acute decompensated HF to stratify patients with high risks for in-hospital mortality and prolonged length of hospital stay. The GNRI, which comprises serum albumin level and ideal body weight, is a simpler index used to assess nutritional status than PNI or CONUT, considering that lymphocyte count is not assessed in the GNRI. It has been reported that the GNRI had the greatest incremental value in predicting the risk of poor prognosis in HF outpatients among the three scoring systems [
23]. Although the clinical utility of the GNRI for predicting long-term mortality in patients with HF has already been reported in several studies [
11,
24,
25], the association between GNRI and in-hospital mortality or length of hospital stay has rarely been investigated. In one study by Aziz and colleagues, nutritional status assessed by the Nutritional Risk Index, which also comprises serum albumin level and ideal body weight, was associated with prolonged length of hospital stay [
26]. However, there are no studies investigating the impact of malnutrition expressed using GNRI on in-hospital mortality and length of hospital stay in patients hospitalized due to acute decompensated HF separately with HFrEF and HFpEF.
In a recent study by Nishino et al., serum albumin levels on admission were associated with prolonged length of hospital stay [
27]. Thus, a novel observation of the present study is that in patients hospitalized due to acute decompensated HF, admission malnutrition based on the GNRI, which can more precisely assess nutritional status compared to other scoring systems, is associated with length of hospital stay in HFpEF but not in HFrEF. Although it is unclear why the GNRI failed to show a statistically significant relationship with either in-hospital mortality or length of hospital stay in patients with HFrEF, age difference may play an important role, as patients with HFrEF are younger than those with HFpEF. According to the Organization for Economic and Cooperation and Development report in 2017, the average length of hospital stay is markedly longer in Japan than in other countries. For patients with HF, a longer hospital stay is a serious problem considering that it negatively affects the patients’ quality of life and increases the patients’ healthcare costs [
8]. Furthermore, HFpEF has recently become highly prevalent in patients hospitalized due to acute decompensated HF, possibly as a result of an increasing elderly population [
28]. Thus, shortening the length of hospital stay for patients with acute decompensated HF and HFpEF is significantly required. Considering the fact that there are no established pharmacological treatments to improve clinical outcomes of HFpEF and that a more comprehensive approach might be necessary to improve the clinical outcomes of HFpEF [
29], it may be worthwhile to investigate whether rapid nutritional intervention can shorten length of hospital stay in elderly patients with HFpEF and malnutrition.
The present study has several limitations. First, because it was an observational study, the results do not confirm the cause-and-effect relationship between malnutrition assessed by the GNRI and in-hospital mortality or length of hospital stay. Thus, further interventional studies are required to confirm this cause-and-effect relationship. Second, in patients with HF, both serum albumin level and body weight are influenced by non-nutritional factors such as fluid overload. Therefore, the measurement of albumin, body mass index, and body weight individually is unsuitable for nutritional assessment in patients with acute decompensated HF. Although using the GNRI as a nutritional indicator may overcome the individual limitations of each indicator [
26], the association between the changes in each indicator during hospitalization and clinical outcomes should be assessed in a further study. Third, this study was a single-center, observational study and included a limited number of in-hospital mortalities. Finally, we cannot exclude the possibility that unmeasured factors may have influenced some of our findings, even after taking confounding factors into account. Thus, the findings of our study should be interpreted with caution.