Abstract
Objective: This study investigates the association between heart rate variability parameters-particularly SDNN or SDANN-and components of intrinsic capacity in older adults, including functional, nutritional, cognitive, psycho-emotional domains, and frailty. Primary outcomes assess the relationship between SDNN and SDANN and frailty status and functional performance (ADL/IADL scores, handgrip strength). Secondary outcomes assess the relationship between SDNN and SDANN and cognitive status (MMSE), nutritional status (MNA, BMI, total protein, hemoglobin, visceral fat), emotional well-being (GDS), and urinary incontinence. Methods: This prospective exploratory study included 83 patients over the age of 65, hospitalized between January and October 2024. All participants underwent cardiovascular evaluation and evaluation of intrinsic capacity (frailty status, ADL/IADL, handgrip strength, MMSE, MNA, GDS, urinary incontinence). Results: Patients were grouped by SDNN values (<128 ms vs. ≥128 ms). Those with lower SDNN had significantly lower MNA scores (p = 0.047), lower hemoglobin (ρ = 0.220, p = 0.046), and higher GDS scores (ρ = -0.219, p = 0.047), indicating poorer nutritional and emotional status. SDANN was negatively correlated with frailty scores (ρ = -0.269, p = 0.014) and positively correlated with ADL scores (ρ = 0.247, p = 0.024), suggesting better functional independence. Handgrip strength was significantly predicted by both SDNN (p = 0.002) and SDANN (p = 0.002) in univariable linear regression. Visceral fat levels were positively correlated with SDNN (ρ = 0.292, p = 0.007), though BMI was not. No significant associations were found between HRV parameters and MMSE scores or urinary incontinence. Conclusions: HRV parameters, particularly SDNN and SDANN, show modest but significant associations with intrinsic capacity components such as frailty, functional performance, nutritional status, and emotional well-being in older adults. These findings suggest that SDNN and SDANN may serve as non-invasive markers for the early identification of declines in intrinsic capacity. Larger longitudinal studies are needed to validate these preliminary results.