Reference values for ambulatory blood pressure and self-measured blood pressure based on prospective outcome data

Although self-measured blood pressure and ambulatory blood pressure are widely used for research and clinical purposes, reference values are still scarcely supported by prospective outcome data. For self-measured blood pressure, values of 135 mmHg systolic and 85 mmHg diastolic (an average of two measurements in the morning and an additional two in the evening for at least 3 working days) have been suggested as the upper-normal reference limits. Unfortunately, these values have received limited support because only one study, the Ohasama study, examined the prognostic value of self-measured home blood pressure. For non-invasive 24 h ambulatory blood pressure, there are at least 11 reports of prospective outcome studies from independent centres that have examined the prognostic values of ambulatory blood pressure, but not all have attempted to define reference values. Currently, an average daytime blood pressure of less that 135 mmHg systolic and less than 85 mmHg diastolic is generally considered to be normal, and a level below 130/80 mmHg may be considered optimal. A reduction in blood pressure of less than 10% from day to night identifies subjects with an increased cardiovascular risk. There is some evidence that cardiovascular risk is further increased when night-time blood pressure is higher than daytime blood pressure. An average 24 h pulse pressure of over 53 mmHg identifies subjects with a raised cardiovascular risk.