Determinants of masked hypertension in hypertensive patients treated in a primary care setting

Background: Recent data suggest that masked hypertension (MH) carries a cardiovascular risk similar to that of uncontrolled hypertension. Aims: The objective of this study was to determine the prevalence and determinants of MH in patients treated for hypertension in a Canadian primary care setting. Methods: Office blood pressure (OBP) was measured at baseline and after 3 months of valsartan-based therapy in 5636 hypertensive patients who had recorded their home blood pressure monitoring (HBPM) for seven consecutive days at month 3 using an Omron HEM-711 apparatus. MH was defined in nondiabetic patients as an OBP < 140/ 90 mmHg and an HBPM >= 135/85 mmHg, and in those with diabetes as an OBP < 130/80 mmHg and an HBPM >= 125/75 mmHg. Results: Of the 5636 patients, 1025 had diabetes. OBP was controlled at 3 months in 268 (26.1%) of them, but 167 (62.3%) had MH. OBP was controlled in 2728 (59.1%) of the 4611 patients without diabetes, and 935 (34.3%) of them had MH. Overall, 1102 patients had MH, representing 36.8% of patients with controlled OBP and 19.6% of the entire hypertensive study population. Stepwise multiple logistic regression analysis in nondiabetic patients with controlled OBP at 3 months revealed that older age, male sex, higher body mass index and higher office systolic blood pressure were determinants of MH. Conclusion: Our results indicate that one of five hypertensive patients and more than one of three with controlled OBP will have MH. MH is associated with other cardiovascular risk factors, such as diabetes, and in nondiabetics, with male sex, older age and obesity.