THE DUBENDORF STUDY - A POPULATION-BASED INVESTIGATION ON NORMAL VALUES OF BLOOD-PRESSURE SELF-MEASUREMENT

There is evidence that self-measurement of BP increases precision, rep roducibility and prognostic value of BP measurement. However, generall y accepted normal values for BP values obtained by self-measurement ar e still missing. The present study was undertaken to investigate diffe rences between office and self-measured blood pressure; 503 randomly s elected inhabitants (265 men and 238 women, age 20-90 years, mean age 46.5 +/- 12.9 years) of the small town of Dubendorf in Switzerland wer e studied. The subjects were not preselected according their BP levels , only patients taking antihypertensive drugs were excluded. Self-meas urement was performed at home by the subjects during 14 days in the mo rning between 6 and 8 am and in the evening between 6 and 8 pm (mean o f 26.7 measurements). Office BP was taken before and after the two wee k period. Mean office BP (130.0 +/- 16.5/82.1 +/- 11.1 mmHg) was signi ficantly (P < 0.01) higher than mean self-measured BP (123.1 +/- 14.6/ 77.6 +/- 10.7 mmHg). There was no significant difference between first and second off ice BP measurement. Morning self-measured BP was lower than evening pressure (DELTA4.0/1.4 mmHg, both P < 0.01) and the mean was taken for comparison with office BP. Both office BP and self-meas ured BP were significantly (P < 0.01) lower in women (off ice BP 126.4 +/- 17.2/79.3 +/- 11.1 mmHg, self-measured BP 118.9 +/- 16.0/74.4 +/- 11.1 mmHg) compared with men (off ice BP 133.4 +/- 15.1/84.7 +/- 10.3 mmHg, self-measured BP 126.9 +/- 12.0/80.5 +/- 9.7 mmHg) but the resu lting mean difference between office BP and self-measured BP was the s ame in men and women. The upper limit of normal office BP has been set at 140/90 mmHg by the WHO. These off ice BP values were at percentile 76.3% (systolic) and 78.4% (diastolic) of the distribution. The corre sponding self-measured BP value at these percentiles was 132.6/85.8 mm Hg. Therefore, we propose a BP of 133/86 mmHg as the upper limit of no rmal for self-measured BP. These results obtained in a representative sample of an adult population confirm that self-measured BP values are lower than casual office BP values and might serve as a guideline for the determination of normal values.