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Background: There is a considerable overlap between the clinical presentation of post-COVID-19 condition (PCC) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Many of their common symptoms can be linked to dysregulation of the autonomic nervous system (dysautonomia). This study aimed to objectively assess autonomic function in a general group of patients with PCC and in a group of patients with ME/CFS whose disease was not related to COVID-19. We hypothesize that the similarity in the chronic symptoms of patients with PCC and ME/CFS extends to objective autonomic nervous system abnormalities., Methods: Synchronous recordings of an electrocardiogram and continuous dynamics of blood pressure in the digital artery using the Penaz method were obtained using the spiroarteriocardiorhythmography method in 34 patients diagnosed with ME/CFS, in whom the onset of the disease was not associated with COVID-19, 29 patients meeting the PCC definition and 32 healthy controls. Heart rate variability (HRV) and systolic and diastolic blood pressure variability (BPV) were assessed at rest and in tests with fixed respiratory rates. Indicators of baroreflex regulation (baroreflex effectiveness index and baroreflex sensitivity) were additionally determined at rest., Results: The total power and power of low-frequency and high-frequency of RR interval variability at rest as well as baroreflex sensitivity were significantly lower both in PCC and ME/CFS patients compared to healthy controls. Several diagnostic prediction models for ME/CFS were developed based on HRV parameters. During slow breathing, the HRV parameters returned to normal in PCC but not in ME/CFS patients. The correlation analysis revealed a close relationship of HRV, BPV parameters and baroreflex sensitivity with fatigue, but not with HADS depressive/anxiety symptoms in the ME/CFS and PCC patients., Conclusions: A similar pattern of HRV and baroreflex failure with signs of a pathological acceleration of age-dependent dysautonomia was identified in the ME/CFS and PCC patients. The clinical, diagnostic and therapeutic implications of these findings are discussed, in light of previously described relationships between inflammation, vascular pathology, atherosclerotic cardiovascular disease and autonomic dysfunction.

The concepts of fragility and resilience are often used together to describe elderly people with reduced physical activity. While fragility, which develops with the aging of the body, is a biological syndrome of a decrease in the stressors response resulting from cumulative regression in many physiological systems, and age related a comprehensive assessment of the ability resistance to stress. In this regard, it is important to develop systems and scales for the identification groups of risk among the elderly. The complexity of the solution lies in the fact that the study of fragility and physical resilience is interdisciplinary, primarily related to the health and increase in the active life of older people. The review describes theories based on the mechanisms of physiological aging, among them the theory of a decrease in the ability to stress, in which stress-related to diseases. The cycles of the development of fragility and a decrease in physiological reserves are considered, and, as a consequence, a change in reactivity to stress, which leads to the development and progression of diseases. The article presents data on homeostatic dysregulation in the accumulation of cumulative deficiency and related changes in heart rate variability, which allows early diagnosis of stressors in the elderly. These data will be useful for the development and implementation of preventive measures aimed at improving the quality of life and resistance to stress factors in elderly and senile people.

The concept of human resilience was created to search for new approaches to improving the well-being of middle-aged, elderly and old people. Resilience is based on the physiological mechanisms of maintaining homeostasis and the ability of organs and tissues to regenerate. Identifying the correlation between environmental factors and the level of reactivity of the body is an important aspect in assessing viability. It contributes to an increase in human life expectancy. Age-related resilience is based on neurophysiological mechanisms of protective processes at different levels, including neural networks and epigenetic mechanisms regulating the expression of MANF, TIMP-2, adropin, irisin, CCL2, CCLR2, β2M genes. The study of medical, psychological, and social indicators of resilience will contribute to the development of new approaches to the correction of age-related pathology.