Association between nocturnal blood pressure dipping and insulin metabolism in obese adolescents.

ABSTRACT

OBJECTIVE: The purpose of this study was to analyze the relationship between insulin-glucose metabolism, nocturnal blood pressure (BP) dipping and cardiac left ventricular mass (LVM) in obese adolescents without diabetes. METHODS: A cohort of 206 obese adolescents (mean age 15.4 years (s.d. 1.6), mean body mass index (BMI) 38 kg m(-2) (s.d. 5.8), 53% girls) under clinical care were included in the study. Body fat was assessed by dual X-ray absorptiometry (DEXA). Blood samples were drawn for analyses of fasting insulin (fS-insulin), fasting glucose and glycosylated hemoglobin Alc. Homeostatic model assessment index (HOMA index) was calculated. Insulin sensitivity and acute insulin response (AIR) were calculated from the performed frequently sampled intravenous glucose tolerance test. An ambulatory BP measurement was performed and 24 h daytime and nighttime values were calculated. Non-dipping was defined as a nocturnal BP reduction of <10%. Ultrasound was used to measure heart LVM and LVM index (LVMI) was calculated (LVM x height(-2.7)). RESULTS: Systolic non-dipping was present in 50% (n=103) of the subjects. Systolic and diastolic dipping was negatively associated with measures of insulin metabolism (HOMA index, fS-insulin and AIR). These associations were present independently of gender, age, daytime BP or body mass index standard deviation score. Dipping (P=0.7-0.9) or measures of insulin-glucose metabolism (P=0.3-1.0) were not associated with LVMI in this population. CONCLUSION: Non-dipping is common among obese adolescents. We found a negative association between nocturnal BP fall (dipping) and measures of insulin metabolism independently of the degree of obesity or daytime BP level among severely obese, non-diabetic adolescents without diagnosed hypertension. Our findings suggest the importance of keeping the insulin levels under observation even in allegedly healthy obese adolescents in clinical care, as a part of the prevention of morbidity associated with obesity.