The Change Of Within-visit Blood Pressure Variability During One Week And The Correlation With Between-visits Blood Pressure Variability

Background:Wide variation in office blood pressure(BP)has resulted in repeated measurement over several visits being recommended by nearly all guidelines.Usually,the variability of repeated BP readings in a single visit is termed within-visit blood pressure variability(BPV),the variability of BP among several visits is termed visit to visit BPV.The aim of this study is to assess the association between the BPV within an initial clinic visit,the variability within subsequent visits,and the variability between visits over one week in a general population.Subjects:The data were obtained from a survey of the general population that was conducted in the adults of three villages of the countryside of Nanchang,Jiangxi,China from March 2017 to May of 2018.Individuals taking anti-hypertensive treatment were excluded from this analysis.BP was measured three times at one-minute intervals on each visit,within one week after the first BP assessment,all participants returned for two further visits on different days which BP was assessed with the same methodology according to the Chinese hypertension guideline standards.The age,gender,habit of smoking,history of hypertension and the information about anti-hypertensive treatment were collected.The difference between maximal and minimal BP readings(△BPmax-min),the standard deviation(SD)and coefficient of variation(CV= 100×SD/mean BP)of 3 BP values in each visit were used to estimate the within-visit BP variability(BPV).The SD and CV on the mean BP values of three visits were used to estimate visit-to-visit BPV.Results:1.After excluding treated hypertensives,the data of 1,401 participants were used in the analysis.Their age ranged from 21 to 94 years(average 62.3±13.7 years old),708 were males(50.5%),693 were females(49.5%)and 293 were smokers(20.9%).2.The average of systolic and diastolic BP(SBP and DBP)decreased from the first to the third visit,the SD and CV for both SBP and DBP also decreased from the first to the third visit.The proportion of △SBPmax-min >10mm Hg were 16.8%,15.2% and 12.1% on three visits respectively,the proportion of △DBPmax-min >10mm Hg were 6.9%,4.1% and 4.2% respectively.3.SD and CV for both SBP and DBP at the first visit were positively and significantly correlated with the corresponding variables computed at the second and third visits.A positive correlation was also found between within-visit BPV at first visit and visit to visit BPV.4.Multivariate analysis showed: no association between average SBP and CV for SBP,but a negative association between average DBP and CV for DBP at the first visit(B=-0.021,P=0.002)and on visit to visit(B=-0.026,P<0.001).Age was positively correlated with CV for SBP on visit to visit(B=0.012,P=0.031),and positively correlated with CV for DBP at first visit(B=0.014,P=0.006).Herat rate(HR)was positively correlated with visit to visit CV for both SBP(B=0.027,P<0.001)and DBP(B=0.017,P=0.017).Smokers had lower BPV compared with nonsmokers.Conclusion:In a general population,within-visit BPV at an initial visit is associated with within-visit BPV at subsequent two visits and with visit-to-visit BPV over three visits within 1 week.Repeated measurement over several visits have important significant for accuracy evaluation of BP and BPV.