Objective: The impact of the day of the week on home blood pressure (BP) level and day-to-day BP profile is unknown. Our objectives were to examine (i) how the initial measurement day of the week affects 3-day and 7-day mean home BP and (ii) the BP variation between different days of the week.
Participants and methods: The study included a population sample of 1852 participants aged 44-74 years. Home BP was measured twice in the morning and evening on 7 consecutive days. The days of the week on which home BP was measured were recorded. BP means were compared with analysis of variance and the t-test.
Results: There were no overall differences in mean systolic/diastolic BPs initiated on various days of the week (3-day means: P=0.15/0.66; 7-day means: P=0.11/0.55). Within-subject systolic/diastolic BP variation between different days of the week was small but significant (128.7±19.2-130.4±19.8/79.5±9.8-80.6±9.9 mmHg; P<0.001/<0.001). Systolic/diastolic BP was lowest during the weekend (Saturday-Sunday: 129.0±18.9/79.6±9.6 mmHg) and highest on Monday (130.4±19.8/80.6±9.9 mmHg), irrespective of the initial measurement day of the week (P for systolic/diastolic difference <0.001/<0.001). In subgroup analyses, the systolic/diastolic BP increase was greater from Saturday-Sunday to Monday among the employed than among the unemployed (1.8/1.3 vs. 0.8/0.7 mmHg; P=0.02/0.01).
Conclusion: Seven-day home BP measurement can be initiated on any given day of the week. However, if a 3-day measurement is taken, it is recommended to keep in mind that BP is usually the lowest during the weekend, and highest at the beginning of the week, especially among the employed.