Age-related changes in phase synchronization of spontaneous mean arterial pressure (MAP) and heart rate (HR) fluctuations within the baroreflex wave range (around 0.1 Hz) were studied in 66 subjects aged 20 to 52 years. During the head-up tilt test, MAP (photocompensation method), ECG (to calculate heart rate), and respiratory rate were continuously recorded. To quantify MAP–HR coupling, the phase synchronization index (PSI) was used. In people over 40 years, an increase in phase synchronization of MAP and HR was found in a supine position compared with subjects aged 20–24 years. At the same time, the increase in PSI of MAP and HR in response to orthostatic stress decreased after the age of 40, which may reflect a decrease in baroreflex activity with age.