Does Nondipping of Blood Pressure at Night Reflect a Trait of Blunted Cardiovascular Responses to Daily Activities?

Background: Individuals who fail to show a decline in blood pressure (BP) when asleep or at night (labeled nocturnal nondippers) are at elevated risk for hypertension and associated target-organ damage. Purpose: We tested whether the well-established changes in BP exhibited in response to daily activities are also blunted in nocturnal nondippers. Methods: Cross-sectional study of 41 women and 56 men, aged 27 to 71 years, residing in Benin, Nigeria, enrolled in a health survey of civil servants. Ambulatory 24-hr BP monitoring was performed with concurrent diary recordings of physical activity level, posture, location, state of mental activity, interpersonal interaction, and mood obtained during the waking hours. Results: Nocturnal nondippers exhibited smaller cardiovascular responses to changes in posture (from lying to sitting or to standing, ps < .02), location (from home to work or to driving/riding in a car, ps < .02), mental activity (from relaxed to active, p =.02), and mood (from feeling mellow to feeling elated-happy, p = .05) than did dippers. Statistical controls for posture substantially reduced the effects of nondipping status on responses to other daily activities and mood. Lack of systolic BP responsiveness to postural changes during the day is a strong predictor of nondipping status. Conclusions: Nondipping at night appears to extend to decreased cardiovascular responses to changes in activities during daytime hours.