Does it matter whether ambulatory blood pressure is recorded during a work day or a non-work day?

OBJECTIVE

To compare ambulatory blood pressure recorded during a work day with that recorded during a non-work day.

DESIGN

A cross-over randomized study in middle-aged treated hypertensives and normotensives.

SETTING

Primary health care.

SUBJECTS

Forty treated hypertensives (20 men) and 40 normotensives (20 men).

MAIN OUTCOME MEASURE

Individual difference between ambulatory blood pressures recorded during a work day and during a non-work day.

RESULTS

The systolic/diastolic blood pressure of the hypertensives was 2/3 (7/5) [mean (SD)] mmHg higher and that of the normotensives 3/3 (5/4) mmHg higher during the work day 24 h monitoring. The blood pressure of the normotensives showed a statistically significant difference between the two monitoring periods both for systolic and for diastolic blood pressure during 24 h and daytime. The corresponding comparison in the hypertensives showed a significant difference only for diastolic blood pressure. During night-time there was no statistically significant difference between the two monitoring periods, neither in the hypertensives nor in the normotensives. Individual comparisons revealed large variations between the two monitoring periods in many subjects. Among the hypertensives the percentage of subjects with a systolic blood pressure difference > 10 mmHg (higher or lower during their work day monitoring period) was 20% during 24 h, 32.5% during daytime and 15% during night-time. The corresponding values for a diastolic blood pressure difference > 5 mmHg were 40% during 24 h, 32.5% during daytime and 40% during night-time. Among the normotensives the corresponding values for systolic/diastolic blood pressure differences between the two monitoring periods were 5/27.5% during 24 h, 5/27.5% during daytime and 2.5/27.5% during night-time.

CONCLUSION

Ambulatory blood pressure recorded during a work day might differ from that recorded during a non-work day. It is important to be aware of this fact when evaluating individual blood pressure graphs, although the importance of this for the development of organ damage is not known. To perform more than a single 24 h blood pressure monitoring can be of value to obtain a better idea of the blood pressure variability of a patient.