The influence of working time on the diurnal variation of blood pressure.

The aim of this study was to compare the diurnal blood pressure (BP) profile in the same persons performing the same work at different hours: at first examination: 06.00 to 14.00 day hours; the second examination: 22.00 to 06.00 night hours. The study group consisted of 20 men working in a power station. They were all doing similar work at the same working place (the handling of electric generators). In each subject 24 h BP monitoring (Excel Oxford Medical) was performed twice, during day and night working hours. Only eight subjects (40%) had a similar diurnal BP profile during both examinations. The BP profile of the other 12 subjects (60%) showed distinct differences. However, we have not observed any common or characteristic pattern in them. These results suggest that the time of working may be an important factor changing the diurnal variation of BP. To ascertain why it is not true for all examined subjects needs further exploration.