Role of the Rhythm Index in Preventive Gerontology and Geriatric Strategies

Role of the Rhythm Index in Preventive Gerontology and Geriatric Strategies

I.V. Kochetkova¹, S.G. Gorelik², A.N. Ilnitskyi³

Irina V. Kochetkova, e-mail: iri4217@yandex.ru

¹N.N. Burdenko Voronezh State Medical University, Voronezh

²Belgorod State National Research University, Belgorod

³Federal Scientific and Clinical Center of the Federal Medical Biological Agency of Russia, Moscow

Background: global population aging actualizes a search for tools for screening early signs of accelerated aging such as presarcopenia (preclinical stage of sarcopenia) and subjective cognitive impairment. Autonomic nervous system dysregulation is a key mechanism of aging and an integral marker of biological age. Rhythm Index (RI) is a convenient indicator of nervous system "tension". Although association of heart rate variability with cardiovascular risk has been proven, role of RI as an integral marker of risks of presarcopenia, cognitive complaints, and accelerated aging is underinvestigated in middle-aged women.

Aim: to evaluate prognostic significance and clinical value of RI as an integral marker of general somatic status, biological age, and risk of presarcopenia in perimenopausal women.

Materials and Methods: data from preventive examinations (n=92458) hosted by N.N. Burdenko Voronezh State Medical University clinics, were used for a primary statistical analysis. Then, a target cohort of women (n=719) aged 40–70 years was formed and divided into seven five-year subgroups. For an in-depth analysis, a relevant point (55 years) justified by statistical modeling methods (piecewise linear regression, p<0.05) and clinical guidelines was identified as a threshold for initiation of active aging and autonomic dysfunction.

To develop a predictive model, a method of feature selection based on an analysis of paired correlations was used. A final regression model included predictors selected from general array of clinical and laboratory data: presarcopenia, SARC-F score, hand strength, MMSE questionnaire, daily heart rate variability (DHRV) based on weighted average rhythmogram variation (WARV), cystatin, omega-3 index, and biological age. Presence of a significant absolute maximum correlation with the integral indicator (RI) was an inclusion criterion for a variable.

The Rhythm Index was determined by a non-invasive method using a heart screening hardware-software package based on microscopic fluctuations of an electrocardiogram signal. RI (%) is a complex quantitative indicator that characterizes stability and regulation of sinus rhythm over a certain period of time (usually over a 5-minute recording). It is calculated as a ratio of total number of cardio intervals (R-R) to number of cardio intervals that differ from a previous one by more than a defined threshold value (usually by 50 ms, or 10%).

Results: 100 55-year-old women were enrolled in the study. In patients with presarcopenia, RI was significantly higher (18.00 [16.00; 25.00] %) than in those without presarcopenia (10.00 [6.00; 15.00] %, p<0.001). RI is a significant predictor of presarcopenia (AUC=0.835; p<0.001). A significant correlation of RI with a number of integral indicators (direct correlation with a SARC-F score (p=0.440; p<0.001), hand strength (p=0.475; p<0.001), cystatin level (p=0.523; p<0.001), and biological age (p=0.691; p<0.001); inverse correlation with WARV (p=-0.603; p<0.001) and omega-3 index (p=-0.551; p<0.001)) was revealed. Linear regression shows that RI explains 45.3% of variability in biological age (p<0.001). A strong direct correlation was detected between RI and a MMSE score (p=0.626; p<0.001).

Conclusion: Rhythm Index is transformed from a narrow indicator of heart rate variability into an all-purpose biomarker of systemic "biological age" and neurovegetative homeostasis. Diagnostically significant threshold RI values (>15%), which have a high differentiating ability to detect pre-disease, have been empirically determined. RI is a highly sensitive integral indicator reflecting a combined effect of behavioral, metabolic, cardiac, and neurocognitive risk factors. This provides new opportunities for preventive gerontology and personalized medicine.

Keywords: rhythm index, preventive gerontology, pre-disease, presarcopenia, risk stratification, personalized prevention.