Ambulatory blood pressure monitoring in clinically healthy subjects adapted to living in Antarctica.

This study investigates 24-h blood pressure (BP) and heart rate (HR) values in clinically healthy subjects adapted to living in Antarctica, as compared to their coeval subjects living in their home country. Its aim is to detect how cardiovascular rhythms behave in those environmental conditions and occupational cues. The 24-h BP and HR values were measured via a noninvasive ambulatory monitor, and statistically analyzed via conventional and chronobiological procedures. The normotensive subjects living in Antarctica were seen to show significant changes in the daily mean level of systolic BP (increase) and HR (decrease) as compared to their controls. In addition, they were seen to show the BP and HR circadian rhythms to be perfectly synchronized to the 24-h cycle, despite the permanent solar light, as an effect imposed by the routines of their local lifestyle. The observed changes reflect a tonic modulation of the BP and HR circadian rhythms which allows the cardiovascular apparatus to adapt itself without imposing an extra load on its function.