S-46-5: THE INTRA-WEEK VARIABILITY ON HOME BLOOD PRESSURE WITH OR WITHOUT ANTIHYPERTENSIVE MEDICATION: NOSE STUDY

Abstract

Objective: Few studies have investigated weekly variations in long-term home blood pressure (BP) measurement. The aim of this study was to examine the intra-week variability and the difference in the day of the week on long-term home BP with or without antihypertensive medication. Design and method: This study was based on an ongoing community-based intervention study in Nose, Osaka, which was designed to assess the effect of home BP measurement on prolonging healthy life expectancy. The study included 510 participants aged 40–91 years. Participants measured their BP with an electronic oscillometric device (HEM-7281; Omron Healthcare CO., Ltd) and wrote the value on the recording book twice in morning and evening for about six months to a year. The intra-week variability in home BP were calculated as maximum minus minimum BP (MMD: maximum-minimum difference). Home BP recording for 62916 days were obtained by extracting weeks in which BP were measured on 7 consecutive days. The participants were divided into 2 groups according to with or without antihypertensive medication. The mean BP values according to the day of the week of home BP measurement were compared by one-way analysis of variance. MMD means were compared with the t-test. To identify the factors influencing on the intra-week variability in home BP, Multiple linear regression models were applied to examine. Results: Among participants without antihypertensive medication, morning systolic BP(SBP) was lowest on Saturday (p < 0.001) as compared with all other days of the week and evening SBP tends to be highest on Sunday. Among participants with antihypertensive medication, morning SBP tends to be lowest on Saturday and evening SBP was highest on Sunday (p < 0.001). The characteristics of the day of the week were similar for the two groups. Antihypertensive medication was not significantly associated with MMD in morning SBP in the multiple linear regression model. MMD in morning SBP had significant positive relationships with female(β = 0.05) and age(β = 0.07), measurement in winter(β = 0.04), morning SBP means(β = 0.25), respectively by p < 0.001. Conclusions: Evening SBP was highest on Sunday regardless of antihypertensive medication. This may be related with clinical evidence that cardiovascular events occur more frequently in the morning on Monday. Considering a variety of factors associated with the intra-week variability in home BP with or without antihypertensive medication, this observation suggested that treatment decisions against hypertension may be based on long-term home BP measurements.