Coexisting Frailty, Cognitive Impairment, and Heart Failure: Implications for Clinical Care

Frailty is a powerful predictor of poor clinical outcomes and mortality in cardiovascular disease [8,9]. Compared with the non-frail, frail persons with heart failure have increased rates of mortality (16.9% vs 4.8%) and increased rates of heart failure hospitalization (20.5% vs 13.3%) [10]. Frailty has also been shown to predict falls, disability, and hospitalization in heart failure patients [6,9,11] and was found to have a negative linear relationship with health-related quality of life [12]. Frail heart failure patients are also more likely to have comorbidities such diabetes mellitus, chronic obstructive pulmonary disease, atrial fibrillation, depression, anemia, and chronic kidney disease [9,13].

Pathophysiology

There is significant overlap in the underlying pathological mechanisms of heart failure and frailty. Symptoms of heart failure, such as dyspnea, fatigue, and muscle loss, mirror components that occur with frailty. Further, cardiac cachexia, a metabolic syndrome in advanced heart failure characterized by a loss of muscle mass, is very similar to the sarcopenia that occurs in frailty.

Frailty, characterized by an increased physiologic vulnerability to stressors, may predispose frail persons with heart failure to exacerbation and worsening of heart failure due to greater susceptibility to the harmful pathophysiologic processes in heart failure, such as inflammation and autonomic dysfunction. Proposed pathophysiologic pathways in frailty include free radicals and oxidative stress, cumulative DNA damage, decreased telomere length, and nuclear fragmentation [14,15]. Frailty has been associated with low-grade chronic inflammation and increased inflammatory cytokines, such as C-reactive protein, tumor necrosis factor–alpha (TNFα), interleukin-6 (IL-6)and fibrinogen [16–18]. Heart failure also is associated with a low-grade and chronic cardiac inflammatory response that is correlated with disease progression [19].

Inflammation. IL-6 is detectable in a higher proportion of persons who are frail compared to non-frail [16] and is the most highly correlated biomarker with frailty. In addition, among those with detectable IL-6 levels, those categorized as frail have higher IL-6 levels compared to those who are non-frail [16,20]. Individuals categorized as frail were found to have significantly higher levels of TNFα than those who were non-frail [16,20]. Increased IL-6 levels are associated with decreased muscle strength, while increased TNFα levels are associated with decreased skeletal muscle protein synthesis [21,22], thus contributing to frailty.

Oxidative stress. Protein carbonyls result from protein oxidation promoted by reactive oxygen species and are markers of oxidative stress. Protein carbonylation is implicated in the pathogenesis of the loss of skeletal muscle mass; high serum protein carbonyls are associated with poor grip strength [23]. 8-OHdG is an oxidized nucleoside indicative of oxidative damage to DNA and a measure of oxidative stress. Accumulation of 8-OHdG in skeletal muscle leads to loss of muscle mass and is associated with decreased hand grip strength in the elderly [24]. Higher serum levels of 8-OHdG are present in older adults who are frail as compared to those who are non-frail [25].

Measurement of Frailty in the Clinical Setting

Frailty has been conceptualized in a number of studies using different models and measures; however, there continues to be a lack of consensus on the definition and operationalization of frailty. Prior research has led to the development of several validated models of frailty that have demonstrated good prediction of adverse outcomes in older adults. Some models, such as the Fried phenotype [6], focus solely on the physical dimension, while other models take a multidimensional approach.Single-item measures (eg, gait speed, 6-minute walk test, handgrip strength) are also commonly used to screen for frailty, but a frailty measure that incorporates more than 1 physical dimension may be more sensitive and reliable. In our opinion, the ideal measure of frailty would consist of a brief assessment that can be serially performed in most clinical practice settings that can identify change in function over time. The incorporation of sensitive physical function measures that can detect frailty early has the potential to slow physical function decline by preserving physiological thresholds.