Nighttime blood pressure versus non-dipping for predicting asymptomatic organ damage in young individuals

BACKGROUND: Circadian blood pressure (BP) phenotypes are associated with cardiovascular risk, though understudied in youth. This study in young individuals investigated the association of nighttime BP with measures of hypertension mediated organ damage (HMOD), primary endpoint of interest in this low absolute cardiovascular risk population. METHODS: Individuals aged 6-25 years were evaluated with 24-h ambulatory BP monitoring (ABPM). HMOD investigation included echocardiographic left ventricular mass index (LVMI) and ultrasonographic common carotid artery intima-media thickness (IMT). RESULTS: Two hundred and seventy-six individuals were included (mean age 13.8 ± 3.8 years, 67% males) with ABPM data (23.6% ABPM hypertension, 26.4% nighttime hypertension, 30.4% non-dippers) and LVMI (n = 257) and/or IMT (n = 205). BP and HMOD indices increased with age, whereas non-dipping prevalence was not associated with age. Non-dippers vs. dippers had higher LVMI (30.5 ± 8.2 vs. 28.4 ± 5.95 g/m2.7, P = 0.01) and IMT (0.52 ± 0.05 vs. 0.50 ± 0.05 mm, P = 0.02), adjusted for age, sex, body mass index z-score (BMIz) and 24-h systolic BP (SBP). Individuals with nighttime hypertension vs. nighttime normotension had higher LVMI (32.76 ± 8.02 vs. 27.69 ± 5.65 g/m2.7, P < 0.001) and a trend towards higher IMT (0.52 ± 0.06 vs. 0.50 ± 0.05 mm, P = 0.16), adjusted for age, sex and BMIz. Dippers and non-dippers with nighttime hypertension had higher LVMI than dippers with nighttime normotension (all P < 0.05). In multivariable models, non-dipping independently associated with LVMI/ IMT (β = -2.14/-0.02, all P < 0.05), after adjustment for 24-h SBP, but not for nighttime SBP (β = -0.9/-0.01, for LVMI/IMT, respectively, all P = NS). CONCLUSIONS: In young individuals asymptomatic HMOD is associated with both nocturnal hypertension and non-dipping. However, nighttime BP levels seem to have the primary contributing role.