Masked hypertension incidence and risk factors in a prospective cohort study

Aims Masked hypertension may affect up to 30% of the general population and is associated with a high cardiovascular disease risk. No previous study has examined the incidence of masked hypertension and its risk factors. The study aim was to determine the incidence of masked hypertension and to examine its related risk factors. Methods This is a cohort study including 1836 initially normotensive participants followed up on average for 2.9 years. Blood pressure was measured using Spacelabs 90207. Manual blood pressure was defined as the mean of the first three readings taken at rest. Ambulatory blood pressure was defined as the mean of the next readings recorded every 15 minutes during daytime working hours. Masked hypertension incidence at follow-up was defined as manual blood pressure less than 140 and less than 90mmHg and ambulatory blood pressure at least 135 or at least 85mmHg. Generalised estimating equations were used. Results The cumulative incidence of masked hypertension was 10.3% and was associated with male gender (relative risk (RR) 1.51, 95% confidence interval (CI) 1.18-1.94), older age (RR40-49 years 1.56, 95% CI 1.16-2.11, RR50 years 1.50, 95% CI 1.06-2.10), higher education (RRcollege 1.31, 95% CI 1.03-1.65), body mass index (RR27 1.43, 95% CI 1.11-1.85), smoking (RR 1.51, 95% CI 1.09-2.010) and alcohol intake (RR6/week 1.65, 95% CI 1.13-2.03). Conclusion The present study is the first to identify risk factors for the incidence of masked hypertension. Current guidelines for hypertension detection recommend ambulatory blood pressure in patients with an elevated blood pressure reading at the clinic. As it is impractical to measure ambulatory blood pressure in all normotensive patients, factors identified in the present study should be considered for the screening of at-risk individuals and for primary prevention of masked hypertension.