Nocturnal Blood Pressure, 3-Methoxy-4-hydroxyphenylglycol and Carotid Intima-media Thickness: The SABPA Study

Background Research demonstrated a significant relationship between elevated nocturnal blood pressure and sympathetic hyperactivity. The study aimed to investigate possible associations between norepinephrine metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), nocturnal BP and carotid intima-media thickness (CIMT) in urban African and Caucasian men. Methods The study included 82 African and 100 Caucasian male teachers, aged 33–56 years, recruited in the North-West Province, South Africa. Ambulatory BP and fasting saliva and blood samples were collected. B-mode ultrasound images were obtained to determine CIMT. Results Despite higher usage of anti-hypertensive medication usage ( p = 0.039), a large number of the African men were nocturnal hypertensives (75, 61%). The nocturnal systolic blood pressure (SBP) ( p < 0.001), diastolic blood pressure (DBP) ( p < 0.001) and heart rate ( p < 0.001) of the African men were higher. After stratifying groups into only nocturnal hypertensives the trend was the same (SBP p < 0.001; DBP p < 0.001; heart rate p = 0.058). In the African and Caucasian men, CIMT was linearly predicted by SBP ( β = 0.33, p < 0.001) and DBP ( β = 0.24, p = 0.016) respectively, but not MHPG. Conclusion No associations were firstly demonstrated between MHPG as sympathetic activity marker and CIMT or secondly, between MHPG and nocturnal blood pressure. Novel findings of elevated nocturnal BP evidently seem to promote structural vascular disease in urban African and Caucasian men.