Population-derived comparisons of ambulatory and office blood pressures. Implications for the determination of usual blood pressure and the concept of white coat hypertension.

BACKGROUND: Ambulatory blood pressures (BPs) have generally been reported to be lower than office blood pressures, but population-based data are lacking.
METHODS: To better characterize ambulatory and office BP relationships, we explored the interrelationships of BPs measured in the office by mercury sphygmomanometry, 24-hour ambulatory BP measured with a portable device, and echocardiographic left ventricular mass in a random sample of 50 men aged 51 to 72 years drawn from a much larger pool. Office BP was based on the mean of 10 measurements performed over five visits.
RESULTS: Among all participants, mean 24-hour ambulatory and mean office BPs were highly correlated: r (systolic/diastolic) = .90/.79; and both mean 24-hour and mean awake ambulatory BPs were significantly higher than mean office BPs. For the subsample not receiving antihypertensive therapy, mean ambulatory and office BPs were similar in terms of their associations with Penn left ventricular mass index (LVMI). No association between BP and left ventricular mass was observed among the subjects receiving antihypertensive medication.
CONCLUSIONS: We conclude that a single session of 24-hour ambulatory BP monitoring is unlikely to improve the determination of usual BP in older white men beyond that achievable with BP carefully measured over five separate office visits; and that white coat hypertension is rare in this population.