Age-related reflex responses from peripheral and central chemoreceptors in healthy men Bartomiej PalecznyPiotr NiewinskiAgnieszka RydlewskaMassimo F. Piepoli • Ludmia Borodulin-NadziejaEwa A. JankowskaBeata Ponikowska

Objective The study aimed: (i) to characterize reflex responses from peripheral and central chemoreceptors in different age groups of healthy men (\50 years old vs C50 years old) and, (ii) to assess, within these groups, whether there is any relationship between ventilatory and hemodynamic responses from chemoreceptors and indices of autonomic nervous system (ANS). Methods Peripheral chemoreflex sensitivity was assessed by the transient hypoxia method and respiratory, heart rate (HR) and blood pressure responses were calculated. Central chemoreflex sensitivity was assessed by the rebreathing method and respiratory response was calculated. ANS was assessed using heart rate variability indices and baroreflex sensitivity (BRS). Results Sixty-seven healthy men were divided into 2 groups:\50 years (n = 38, mean age: 32 ± 10 years) and C50 years (n = 29, mean age: 61 ± 8 years). There were no differences in respiratory response from central and peripheral chemoreceptors between the older and younger groups of healthy males. We found a significantly different pattern of hemodynamic responses from peripheral chemoreceptors between the older and the younger groups. The former expressed attenuated HR acceleration and exaggerated blood pressure increase in response to transient hypoxia. Blunted HR response was related to reduced BRS and sympathovagal imbalance characterized by reduced vagal tone. Blood pressure responses seemed to be independent of sympathovagal balance and BRS. Interpretation Ageing impacts hemodynamic rather than respiratory response from chemoreceptors. Impaired arterial baroreflex and sympathovagal imbalance related to ageing may contribute to decreased heart rate response, but not to increased blood pressure response from peripheral chemoreceptors.