By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.
People who monitor their blood pressure usually take the readings early in the morning or in the evening. A commonly asked question is whether there is a consistent difference between morning and evening readings. A few studies have looked at this, but the numbers of patients included has been relatively small. Now a large Japanese study has provided a definitive answer.
The residents of Ohasama, a small town in Japan, were invited to monitor their blood pressure at home. Twelve hundred took readings both in the morning, soon after getting up, and in the evening, before going to bed, for at least two
weeks. Readings were taken with an Omron automatic recorder. The average blood pressure measured in the clinic was 131/76 mmHg. The home pressures were
122/76 in the morning, and 120/75 in the evening. In people who had high blood pressure, the difference between morning and evening blood pressures was a little bigger.
This is the largest study to examine the difference between morning and evening blood pressures. Although the morning pressures were consistently higher than the evening pressures, the differences were quite small, particularly when compared with the difference between the clinic pressures and the home pressures.
Where it was published
Y Imai and colleagues. Characteristics of blood pressure measured at home in the morning and in the evening : the Ohasama study. Journal of Hypertension 1999; 17:889-898.