Nocturnal blood pressure, 3–methoxy–4–hydroxyphenylglycol and carotid intima–media thickness: the SABPA study

Abstract

Background: Research demonstrated a significant relationship between elevated nocturnal blood pressure and sym-pathetic 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 Africanand Caucasian men.Methods: The study included 82 African and 100 Caucasian male teachers, aged 33–56 years, recruited in the North-WestProvince, South Africa. Ambulatory BP and fasting saliva and blood samples were collected. B-mode ultrasound imageswere obtained to determine CIMT.Results: Despite higher usage of anti-hypertensive medication usage (p = 0.039), a large number of the African menwere 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 nocturnalhypertensives the trend was the same (SBP p < 0.001; DBP p < 0.001; heart rate p = 0.058). In the African and Caucasianmen, 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 orsecondly, between MHPG and nocturnal blood pressure. Novel findings of elevated nocturnal BP evidently seem topromote structural vascular disease in urban African and Caucasian men.