NIGHTTIME BLOOD PRESSURE PHENOTYPES AND PRECLINICAL TARGET-ORGAN DAMAGE IN YOUNG INDIVIDUALS

Objective: To investigate the relationship between nighttime blood pressure (BP) phenotypes with indices of preclinical target organ damage (TOD) in healthy young individuals. Design and method: Individuals (aged 6-25 years) referred for suspected hypertension were evaluated with 24-hour ambulatory BP monitoring (ABP). Nighttime hypertension was defined as nighttime systolic and/or diastolic ABP above reference normal values according to pediatric guidelines. Non-dippers were defined as those with systolic and/or diastolic nighttime dip <10%. TOD was assessed by echocardiographic left ventricular mass index (LVMI) and ultrasonographic determination of intima-media thickness of the common carotid artery (IMT). Results: Analysis included 276 individuals (13.8±3.8 years, 67% males) with ABP and data on LVMI (n=257) and/or IMT (n=205). Based on ABP 23.6% had hypertension and 26.4% nighttime hypertension, 69.6% were dippers. Non-dippers versus dippers had higher nighttime (114±11.05 vs. 108±10.08 mmHg, p<0.05) and lower daytime systolic BP (122±11.46 vs. 126.2±11.25 mmHg, p<0.05), after adjusting for age, sex, body mass index z-score (BMIz) and 24 h systolic/diastolic BP. Nighttime hypertension was more prevalent in non-dippers than dippers (40.5% vs. 20.3%, p=0.01). Non-dippers showed higher LVMI (30.5±8.2 vs. 28.4±5.95 g/m2.7, p=0.04) and IMT (0.52±0.05 vs. 0.50±0.05 mm, p=0.04). Individuals with nighttime hypertension compared to those with nighttime normotension had higher LVMI (32.76±8.02 vs. 27.69±5.65 g/m2.7, p<0.001) and IMT (0.52±0.06 vs. 0.50±0.05 mm, p=0.02). Non-dippers with nighttime hypertension had higher LVMI than dippers with normal nighttime BP (p=0.01 after Games-Howell correction). Dippers with nighttime hypertension showed higher LVMI than both dippers and non-dippers with nighttime normotension (p<0.03 after Games-Howell correction). IMT tended to be higher in dippers with nighttime hypertension compared to dippers with normal nighttime BP (p=0.06 after Tukey HSD correction). In stepwise multivariable linear regression analysis, non-dipping was independently associated with LVMI (β=2.14, p=0.01) and IMT (β=0.02, p=0.02), after adjustment for sex, age, BMIz and 24 h systolic ABP. However, after adjustment for nighttime systolic BP levels (instead of 24 h systolic BP), this association lost its statistical significance. Conclusions: In otherwise healthy young individuals both nocturnal hypertension and non-dipping are associated with TOD but nighttime hypertension seems to be the main determining factor.