Variability of home blood pressure measurements between first and second measurements on one occasion, and factors related to variability.

The number of home blood pressure (BP) measurements on one occasion has continued to be discussed. Therefore, we evaluated the variability of the first and second measurements on one occasion. The subjects except hypertensive patients (393 males, 212 females; mean age 38.7 y) were recruited from one company. Home blood pressure was measured with a semiautomatic device, and subjects were instructed to perform triplicate morning and evening measurements on 7 consecutive days. The standard deviation of systolic blood pressure (SBP) was significantly greater in the first measurement than in the second measurement, but there was no significant difference in standard deviation of diastolic blood pressure. As for the coefficient of variation (CV), CV of morning SBP alone was significantly greater in the first measurement (5.3% ± 0.1%) than in the second measurement (4.9% ± 0.1%). Therefore, factors related to CV of morning SBP in the first measurement were studied, which indicated that it was significantly greater in smokers (5.8% ± 0.1%) than in nonsmokers (5.2% ± 0.1%), and in women (5.6% ± 0.1%) than in men (5.2% ± 0.1%). In conclusion, CV of morning SBP was significantly greater in the first measurement than in the second measurement. The coefficient of variation of morning SBP in the first measurement might be influenced to some extent by the presence or absence of smoking habit and gender. Therefore, physicians should pay special attention to the above-mentioned fact in the future.