Cardiovascular rhythms, their adjustment to schedule change and shift work

With illustrative chronobiologic methodology, the rules of rhythm shifting by work schedule manipulation are reviewed with reference to self-measured or ambulatory blood pressure and heart rate. The literature on the cardiovascular performance of shift workers studied with miniaturized devices or by self-measurement is reviewed and the systolic blood pressure status of 36 police officers presented. 53% of these officers had blood pressure excess assessed as the area between the blood pressure curve where it exceeds a time-varying peer-group limit and this limit itself, computed in mm Hg × hour by numerical integration. The cosinor approach defines blood pressure characteristics and their deviation with respect to those of healthy peers by fitting cosine curves for assessing static and dynamic parameters such as midline-estimating statistic of rhythm M (MESOR), the rhythm-adjusted mean; amplitude A, the measure of the extent of predicted change; acrophase Φ, the timing when most of the high readings occur; and period; as well as measures of waveform. Some of these chronobiologic endpoints are introduced in this minicourse to stimulate their use in particular for individuals under a burden such as police work on shifting schedules.