Frailty Shifts Linked to Cardiovascular Outcomes in Intensive Blood Pressure Control Trial
A new analysis of the SPRINT trial reveals that changes in frailty status over a one-year period are significantly associated with cardiovascular events, mortality, and serious adverse events, even within the context of intensive blood pressure control. The findings underscore the importance of considering frailty as a key factor in managing cardiovascular risk, particularly in older adults.
The SPRINT (Systolic Blood Pressure Intervention Trial) was a landmark, open-label randomized controlled clinical trial designed to assess the impact of intensive versus standard blood pressure control on cardiovascular outcomes. Conducted across 102 clinical centers in the USA, the trial enrolled 9,361 participants aged 50 and older with elevated systolic blood pressure (130-180 mmHg) and increased cardiovascular risk. Increased risk was defined by the presence of existing cardiovascular disease, impaired kidney function, a high Framingham Risk Score, or age 75 or older. Participants were assigned to target systolic blood pressures of less than 120 mmHg (intensive control) or less than 140 mmHg (standard control). The study was approved by Institutional Review Boards and involved informed consent from all participants.
Researchers have now conducted a post hoc analysis focusing on changes in frailty among SPRINT participants. Frailty, a state of increased vulnerability to stressors, was assessed using the SPRINT frailty index (FI), a 33- or 34-item measure incorporating factors like self-reported health, cognitive performance, blood pressure, lab measurements, and comorbidities. Gait speed was also included for participants aged 75 and older. The FI ranges from 0 to 1, with higher scores indicating greater frailty. Participants were categorized as either frail (FI > 0.21) or robust (FI ≤ 0.21) at baseline and 12 months, allowing researchers to track changes in frailty status – stable-robust, robust-to-frail, frail-to-robust, and stable-frail.
Data collection involved comprehensive assessments of socio-demographics, medical history, medications, and quality of life, conducted at baseline and annually. Blood pressure was monitored frequently, and blood tests, electrocardiograms, and dementia screenings were performed at regular intervals. Urine samples were also analyzed to assess kidney function.
The analysis revealed distinct characteristics among the different frailty status groups. Those who transitioned from robust to frail exhibited notable differences compared to those who remained robust, while those who improved from frail to robust showed contrasting profiles. These differences highlight the dynamic nature of frailty and its potential for intervention.
Using Kaplan-Meier curves and Cox proportional hazards regression, the researchers found that changes in frailty status were significantly associated with major cardiovascular events (a composite of myocardial infarction, stroke, heart failure, and cardiovascular death) and all-cause mortality. Specifically, individuals who became more frail experienced a higher risk of adverse outcomes. The hazard ratios (HRs) and 95% confidence intervals (CIs) demonstrated the strength of these associations, with the stable-robust group serving as the reference point.
Furthermore, the study examined the relationship between the change in frailty index (∆FI) and clinical outcomes. Categorizing ∆FI into tertiles and using a minimal clinically important difference (MCID) threshold of 0.03, researchers observed a dose-response relationship: greater increases in frailty were associated with increased risk.
The impact of intensive blood pressure treatment was also evaluated in relation to frailty status. Researchers assessed whether the benefits of intensive BP control varied depending on a patient’s baseline frailty or changes in frailty. They calculated the number needed to be exposed (NNEB) for benefit and the number needed to be harmed (NNEH) to quantify the treatment effect in different frailty groups. Interaction terms were added to the models to test for statistically significant differences in treatment effects based on frailty.
Several sensitivity analyses were conducted to ensure the robustness of the findings. These included using a competing risk model to account for mortality and alternative methods for calculating the frailty index. All statistical analyses were performed using R software version 4.2.2 and SAS version 9.4.
These findings suggest that frailty is an independent predictor of cardiovascular outcomes and mortality, even in the context of intensive blood pressure control. The study highlights the potential for interventions aimed at preventing or reversing frailty to improve cardiovascular health, particularly in vulnerable older adults. Further research is needed to identify effective strategies for mitigating frailty and optimizing treatment approaches based on individual frailty profiles. .
