[Reduced nocturnal systolic blood pressure dip in obese children]

Ambulatory blood pressure monitoring (ABPM) allows evaluation not only of casual daytime elevations of blood pressure (BP) but also alterations in the 24-hour circadian patterns of BP. The aim of the present study was to assess 24-hour BP patterns in a population of obese children who were referred to our outpatient clinic, in relation to the degree of obesity, body fat distribution and insulin resistance, and considering other cardiovascular risk factors.

Office and ambulatory BP measurements, and fasting serum glucose, insulin and HOMA determinations were obtained in 119 obese children (7-15 years old). Urinary albumin excretion was measured in the first morning urine. The extend of obesity was quantified using body mass index z score adjusted by age and gender.

The prevalence of office hypertension in only one set of blood pressure measurements was 47%. This value was not confirmed on further separate occasions. The prevalence of global ambulatory hypertension was 36%. Diurnal systolic hypertension was found in 14%, while 39 patients (33%) had nocturnal systolic hypertension. Twenty five of them (64%) were only hypertensive at nightime and the rest (n = 14), were also hypertensive during the day. Only 4 patients were exclusively systolic hypertensive at daytime (table III). None of the patients were exclusively diastolic at day or nighttime. Of the total 119 subjects 47% non systolic dippers. This abnormal BP pattern was associated with the degree of obesity (p < 0.001) and insulinresistance (HOMA values; p < 0.001). The anthropometric and metabolic characteristics of the population studied are shown in table I and II respectively. The correlations coefficients and regression analysis between anthropometric and metabolic parameters are shown in table IV and V.

Reduced nocturnal systolic blood pressure dip and nightime systolic hypertension were the most frequent forms of hypertension in our cohort of severe obese children. These alterations in the 24-hour circadian patterns of BP were related to the degree of obesity and insulin resistance.