Introduction
Older adults typically receive a frailty diagnosis through two established models the phenotypic approach and the deficit accumulation index. The phenotypic model defines frailty as a clinical syndrome that requires three out of the following five physical criteria: unintentional weight loss, exhaustion, weakness, slowness, and low physical activity. The frailty Index defines frailty as a measurable scale that calculates health deficits (including diseases, disabilities, and laboratory abnormalities) against the total number of assessments to show the total health burden. The two definitions of frailty remain valid yet differ in their approach because the phenotypic model uses physical symptoms for clinical screening while the frailty Index evaluates overall vulnerability through multiple health domains. The two models provide distinct advantages for research and clinical practice which together improve our understanding of frailty as a complex multidimensional condition [1].
Functional dependence and frailty are closely intertwined, often reinforcing one another in a cyclical progression. The FREEDOM-LNA study revealed that a substantial portion of older adults were both frail or pre-frail (approximately 90%) and exhibited high rates of dependence in basic and instrumental activities of daily living (66.9% and 85.1%, respectively). Functional dependence may lead to frailty by reducing mobility, physical activity, and autonomy, all of which are essential to preserving muscle strength, endurance, and overall physiological reserve. Conversely, frailty can precipitate functional decline, increasing the need for assistance in daily tasks, and in certain clinical scenarios, the temporal interaction between functional dependence in basic activities of daily living and frailty may exhibit bidirectional causality [2].
Both frailty and functional dependence frequently coexist in the context of older adults with comorbidities or pluripathology, which carry adverse health outcomes, as well as an increase in the use of resources including social and health care in outpatient and inpatient settings (in pre-frail and frail older adults) and in the home setting (in patients with significant functional dependence) [3]. The chronic pathologies most commonly described in this population differ according, to the scope, and purpose of the studies, but in general they include cardiovascular, oncologic, rheumatologic, pneumopathies and diabetes mellitus type 2 [3]. According to data from the National Household Survey (ENAHO) for the fourth quarter of 2023, 78.9% of the older adult population in Peru reported having at least one chronic health condition. The most prevalent conditions included hypertension (36.3%), metabolic syndrome (31.0%), obesity (8.4%), diabetes mellitus (6.0%), low high-density lipoprotein (HDL) cholesterol (47.3%), hypertriglyceridemia (35.8%), hypercholesterolemia (28.4%), and elevated low-denisty lipoprotein (LDL) cholesterol (7.4%). Men exhibited a lower prevalence of obesity, metabolic syndrome, and dyslipidemia compared to women [4]. These diseases are associated with the frailty syndrome and the different levels of functional dependence that increase the use of health care services and the need for this system to adapt to their requirements.
It is estimated that the prevalence of older adults in pre-frail and frail states and who live in communities of medium and low-income countries is approximately 49% and 17%, respectively, with the prevalence of frailty in the hospital setting being close to 42% [5, 6]. Several risk factors for developing frailty have previously been studied and classified into four large groups: physiological, medical, socioeconomical and psychological [7]. A recent study found that characteristics such as age, sex, polypharmacy, nutritional status, comorbidities, cognitive impairment, depression, and social risk are risk factors for frailty. These findings are consistent with other studies [8, 9].
It is well known that frailty not only predisposes patients to the loss of functionality but is also associated with a greater probability of visits to emergency services, hospitalization (including long term hospitalization), institutionalization, readmissions, and an increase in mortality [3]. The risk of disability elevated 2.1-fold in pre-frail and 2.7-fold in frail older adults [10]. The probability of hospitalization of older adults during the different stages of functional dependence determined by the pre-frail and frail states varies according to the type of disease, which have completely different health care requirements depending on the acuteness or chronicity of functional dependence [11].
Frailty and functionality are related to one another. Not only because the latter is the main result of the first, but also because they share a common approach towards a general objective of an active ageing without disabilities. The coexistence of frailty and functional dependence, within the context of comorbidity, has been associated with different negative outcomes such as high hospital mortality [12]. There is a discrepancy in the scientific literature regarding the impact of frailty, functional dependence and their coexistence, on the number of hospitalizations, therefore, the purpose of this investigation was to determine if the need for hospitalization is more frequent in patients with both frailty and functional dependence compared to patients with only frailty or functional dependence. We also performed an analysis stratified by sex.
Material and methods
Study design and participants
We performed an observational, analytic, retrospective cohort study that analyzed a secondary database of a study including a population of 1896 older adults cared for by the Geriatric Service of the “Naval Medical Center” of Peru from 2010 to 2015 [13]. The study population included older adults (≥ 60 years) of both sexes, who lived in Lima or Callao, and received care on an outpatient basis. The exclusion criteria were: consent not provided, inability to undergo the evaluation, no contact information available, inability to leave home, receiving home medical care, and patients who were hospitalized and presented cognitive impairment or previously diagnosed severe mental disease.
The secondary analysis included the data of all participants. However, participants with missing information related to “weight loss” (31 participants), “walking speed” (92 participants), “physical activity” (139 participants), and “physical exhaustion” (72 participants) were excluded from the study as were 37 patients for whom data related to the Barthel Index were missing. Finally, the data of 1,525 participants were analyzed.
With the use of a formula comparing the mean and assuming an average number of hospitalizations per year of 2.43 in patients with coexisting frailty and functional dependence, with an average of 0.87 hospitalizations per year in patients without functional dependence, with a global standard deviation of 1.36, a sample size of 1,525 with an a 5%, the power of the study was of 99% [14].
Data collection process
The patients were enrolled by telephone during a day scheduled for their appointments, and their information was registered in the database. Follow-up was performed every 6 months from the first months of 2010 until December 2015. The sample was probabilistic. The evaluations were performed at the Day Clinic and the Geriatric Service of the Naval Medical Center by 6 geriatric specialists who performed the patient enrollment, the verification of inclusion and exclusion criteria, and the evaluation of this study.
Study variables:
Frailty: Operationally defined and evaluated by the Fried Phenotype and includes 5 criteria [1]. Walking speed: which is considered low when below 0.8 m/s, according to the European Working Group on Sarcopenia in Older People 2019 [15].
Muscular strength: measured by a dynamometry, on the dominant hand, with a cutoff point for grip strength of < 27 kg for males and < 16 kg for females [15].
Self-reporting of weight loss: reported according to an item in the Edmonton Frail Scale [1, 16].
Physical exhaustion: defined by three positive responses to the following questions: (in the last 2 weeks) Did you feel full of energy? (yes or no); Did you feel you could not go on? (yes or no); Did you feel all you did was with effort? (yes or no). A score ≥ 2 was positive for exhaustion [17].
Physical activity: measured using the Physical Activity Scale for the Elderly (PASE) which has 12 items. Poor physical activity was considered with a score was < 64 in males and < 52 in females [18, 19].
When there is an absence of the previously mentioned criteria a patient is considered as not having frailty, while the presence of 1 or 2 criteria is considered as pre-frailty, and the identification of 3 or more criteria is considered as frailty [20].
Functional dependence: Defined by the Barthel Index which is made up of 10 questions related to the basic activities of daily living. The score ranges from 0 to 100, with a score less than 100 being considered as functional dependence [21].
Coexistence of frailty and functional dependence: defined as the presence of 3 or more criteria of frailty and dependence for basic activities of daily living.
Number of hospitalizations: a numerical variable constituting the number of hospitalizations per year. The information was obtained through an interview with the patient and was verified by the clinical history during the interview. Hospitalizations in the geriatrics and internal medicine departments originating from outpatient referrals or emergency admissions were included; admissions for routine diagnostic evaluations were excluded.
Sociodemographic variables: age, sex, marital status (single, married, widowed, divorced), education (technical/higher, grade school complete/incomplete).
Presence of comorbidities: the medical comorbidities were considered as numerical variables corresponding to the sum of previous pathological conditions such as: diabetes mellitus, chronic renal disease, arterial hypertension, vascular insufficiency, congestive cardiac insufficiency, periodontal disease, chronic obstructive pulmonary disease, depression, knee arthrosis, cerebrovascular disease, hypothyroidism, hip fracture, other fractures, and urinary incontinence evaluated as items of the Edmonton Frail Scale [16].
Statistical analysis
The analysis of the data was performed using the program STATA version 15.0. For the descriptive analysis, the categorical variables were expressed as frequencies and percentages, while the numerical variables were expressed as means and standard deviations. For the bivariate variables, the dependent variable did not have a normal distribution according to the histogram and the Shapiro-Wilk test, therefore, for the analysis of numerical variables with the dependent variable, Spearman correlation was used. For the analysis of the dependent variables with dichotomous categoric variables the Student’s t-test was used and for the analysis of the dependent variable with the polytomous categoric variables the ANOVA test was used. Finally, a stratified analysis by sex was performed using the Kruskal-Wallis test. P-values less than 0.05 were considered statistically significant.
Ethical considerations
The present study used a completely anonymous database and was approved by the Ethics Committee of the Naval Medical Center. Furthermore, the secondary analysis was approved by the Institutional Ethics and Investigational Committee of the Universidad Cientifica del Sur (code number 579-2020-PRE15).
Results
The mean age of the older adults included in the study was 78.6 ±8.5 years; 58.4% (n = 890) of the population were male, 73.6% (n = 1,100) were married and 75.4% (n = 1,136) had a complete or incomplete grade school education. Regarding frailty, 30% (n = 457) had at least one criterion according to the Fried phenotype, and 38.1% (n = 581) presented functional dependence. With regard to the coexistence of frailty and functional dependence, 16.7% (n = 255) were considered dependent and frail, and the mean number of hospitalizations per patient was 1.28 ±1.34 (Table 1).
Table 1
Descriptive analysis of the study variables (n = 1,525)
The bivariate analysis showed a statistically significant association between age, education, the number of comorbidities, frailty, and the coexistence of frailty and functional dependence. It was also observed that the greater the age and number of comorbidities were, the greater was the number of hospitalizations. Likewise, a higher mean number of hospitalizations was found among the participants that had a technical or higher education compared to those with only a grade-level education. In addition, the coexistence of frailty and functional dependence was significantly related to a higher number of hospitalizations compared to other groups (Table 2).
Table 2
Relationship among variables, covariables, and number of hospitalizations (n = 1,525)
Finally, the analysis of the coexistence of frailty and functional dependence and the number of hospitalizations stratified by sex, showed an association in both sexes. Likewise, there was a greater mean number of hospitalizations in frail older women and men with both frailty and functional dependence (Table 3).
Table 3
Analysis of the association between the coexistence of functional dependence and frailty and the number of hospitalizations (n = 1,525)
Discussion
The present study found that the occurrence of functional dependence together with frailty is associated with a greater number of hospitalizations in older adults of both sexes. In fact, 16.7% of the study population were considered frail and dependent. These results are similar to those of previous studies [10, 11, 22]. This association can be explained by different conditions found in the frailty syndrome, such as a state of inflammatory neuroendocrine deterioration and the presence of sarcopenia, which predisposes a greater risk of infection, fracture, falls, and even the presence of other geriatric syndromes. Likewise, the development of physical and cognitive disability can lead to acute or chronic functional dependence.
The time at which functional dependence occurs in older adults is related to the condition known as inflammaging. This condition moderates the coexistence between frailty and functional dependence and depends on the presence of aggregated factors in older adults, such as the accumulation of chronic pathologies associated with aging as well as nutritional, cognitive, and psychosocial status [23].
The bivariate analysis showed a statistically significant association between the number of hospitalizations and age, education, number of comorbidities, frailty, and the coexistence of frailty and functional dependence. These findings are supported by previous international studies which reported that the presence of risk factors, such as sociodemographic determinants and deterioration of health status, was associated with higher hospitalization rates [24–26]. The relationship between the coexistence of the mentioned pathologies and age is explained by the physiological principles of aging that primarily include immunological dysfunction, neuroendocrine dysregulation, and sarcopenia which contribute to the development of a state of frailty which, at the same time, is considered the main predictor for different adverse effects such as greater hospital admissions, an increase in morbidity and mortality, early readmission, prolonged hospitalizations, and institutionalizations, among others [3, 27].
This study also demonstrated that the greater the age and multimorbidity, the greater the frequency of hospitalization. These findings are explained by the overlap between frailty, comorbidities and disabilities, which favors the appearance of the previously mentioned adverse effects. It is known that the associations among these three conditions and the utilization of health care services differ among different age groups. Indeed, an independent association among these three conditions and a greater use of medical services, including hospital admissions and specialized or general outpatient services, has been demonstrated [3, 11] thereby supporting the synergic effects of these three conditions towards the utilization of health care services.
Additionally, it was observed that the coexistence of frailty and functional dependence leads to more frequent hospital admissions compared to other patient groups. These findings are similar to a study that demonstrated that the risk of hospitalization was greater in patients with functional dependence in comparison to other groups. This association fluctuated among the different age groups, and it was demonstrated that the greater the age, the greater the functional dependence and the risk of hospitalization decreased. On the other hand, among the patients evaluated for frailty, the risk of hospitalization increased with age [11]. The high level of functional dependence associated with a lesser risk of hospitalization could be attributed to the fact that when home health services are used, hospitalizations are less frequently required.
Furthermore, in the analysis according to sex, this study demonstrated a significant association between the coexistence of frailty and functional dependence and the number of hospitalizations in both men and women. Likewise, hospital admissions were more frequent in women and in men with both frailty and functional dependence. Regarding the stratification by sex, it is well known that the prevalence and incidence of frailty differ between men and women, with a predominance of the female sex. This may be explained by the longer life span of women with a subsequent higher probability of developing this syndrome. In addition, women have a different body composition that consists of a lower percentage of lean mass and muscle strength [9, 28]. Finally, a metanalysis corroborated that the risk of functional dependence in frail patients is high in both men and women, and frailty was described as a state that precedes functional dependence [29].
The limitations of this study are related to the scarce number of scientific articles that analyze variables related to the coexistence of functional dependence and frailty, both of which are present during a limited time in the life of older adults. Additionally, the data used analyzed in this study was from a hospital cohort, and frailty, functional dependence and the use of health care services could be more frequent in comparison to other cohorts evaluating older adults in the community. In addition, the population analyzed was attended in a naval medical center, and thus, the sociodemographic conditions and access to the health services were different from those of the general Peruvian population. Finally, data on patients’ length of hospital stay were not available. Nevertheless, the results found in this study are interesting, novel, and will help to understand the complex interaction between frailty and functional dependence that is closely related to morbidity and mortality and to the great effect that diseases have on older adults.
