Discrepancy among three blood pressure readings within one measurement and relevant influencing factors

To investigate the discrepancy in three blood pressure (BP) readings within one measurement and the relevant influencing factors.

BP was measured by senior experienced physicians three times at 2-min intervals in 2087 adults (1025 male and 1062 female) with a calibrated mercurial sphygmomanometer. According to the history of hypertension and use of antihypertensive drugs, the participants were divided into hypertensive (EH group, 496 cases, 365 on antihypertensive therapy and 131 not on therapy) and normotensive groups (NT group). The average of three BP readings was used as the basic BP. The discrepancy in systolic BP (DeltaSBP) and diastolic BP (DeltaDBP) was the difference between the maximal and the minimal SBP and DBP of three readings respectively. The ratios of DeltaSBP/SBP and DeltaDBP/DBP were calculated from DeltaBP and the basic BP respectively.

The DeltaSBP of more than 10 mmHg occurred in 19.9% of the population and DeltaDBP of more than 5 mmHg in 32.3% of the population. Rank correlation showed a positive relationship between the basic SBP and DeltaSBP (r=0.109, P=0.001), but no relationship was found between basic SBP and DeltaSBP/SBP. Although the SBP and DeltaSBP were higher in the EH group than in the NT group, no significant difference of DeltaSBP/SBP was found between the EH group and the NT group. A positive relationship between age rank and DeltaSBP (r=0.124, P<0.01) and between age rank and DeltaSBP/SBP (r=0.151, P<0.01) existed in the whole population before elderly. Meanwhile, a stronger relationship between age rank and DeltaSBP/SBP was found in females (r=0.163) than in males (r=0.146). Significantly higher DeltaSBP and DeltaSBP/SBP and DeltaDBP and DeltaDBP/DBP were found in females than in males at lower SBP and DBP levels.

The discrepancy in the three BP readings within one measurement is quite large. High basic BP, female sex, and aging are facilitating factors for large SBP discrepancy. Female sex and aging are independent factors for large discrepancy in three BP readings.