Authors: Cheung BMY and Cheung AJ
Aim: Clinic blood pressure (BP) is only an approximate measure of the true blood pressure. It tends to decrease towards the true value on repeated measurements. The aim of this analysis was to identify the factors related to the change in systolic and diastolic BP on repeated measurements.
Methods: Data on BP and other clinical characteristics were obtained from the National Health and Nutrition Examination Survey (NHANES) database. In 2007-8, there were 4943 participants aged 20 or over with repeated BP measurements. Repeated measurements analysis of variance was used to identify variables related to the change in BP with time.
Results: As expected, BP was significantly related to age, gender and body mass index (P<0.001). Systolic and diastolic BP both decreased significantly with time (P<0.001). The decrease in systolic and diastolic BP with time was significantly related to age and the maximum cuff pressure (P<0.001). It was not related to body weight, arm dimension, triceps skinfold thickness, cuff size, and consumption of food, coffee and tobacco in the preceding 30 minutes. For systolic BP, the decrease was negatively related to the pulse rate (P<0.001). Conclusion: Older persons and those with high systolic BP had a larger fall in BP on repeated measurements. Hence, adequate inflation of cuff and repeated measurements in the elderly are key factors in measuring clinic BP. Keywords: blood pressure; blood pressure measurement; NHANES