Assesment of the relationship between inflammatory markers and ambulatory blood pressure variability and blood pressure circadian variation

Nowadays, results of several studies have shown that ambulatory blood pressure correlates with hypertension related organ damage more closely than does office blood pressure and has a relationship with cardiovascular events that is steeper than that observed for clinic blood pressure, with a prediction of cardiovascular risk greater than, and additional to the prediction provided by office blood pressure values in populations as well as in untreated and treated hypertensives. Recent data has also shown that blood pressure variability estimated as a standard deviation of non-invasive ambulatory blood pressure monitoring is also associated with cardiovascular morbidity and mortality. Cardiovascular morbidity has been reported to be greater in subjects with a greater blood pressure variability than in those with a lower blood pressure variability. Relationship between circadian blood pressure variation and cardiovascular mortality and morbidity is well known. Subjects in whom nocturnal blood pressure decrease is blunted (less than 10%) have been reported to have less favourable outcome. However there is growing evidence suggesting a link between hypertension and inflammatory system, yet data on the association between inflammatory markers and blood pressure variability in humans are sparse. We performed a prospective, cross-sectional study in order to examine whether inflammatory factors might be associated with elevated blood pressure variability during 24-hour ambulatory blood presssure monitoring. The study population was a sample of subjects admitted to Baskent University Hospital, Department of Cardiology. Subjects were eligible to participate in the study if they were 20 to 60 years of age, had no histories of hypertension and were not using antihypertensive medications, had no histories of cardiovascular disease (coronary artery disease, stroke, peripheral vascular disease), were free of any other major systemic illnesses, and were not pregnant. We recruited 198 subjects (102 women and 96 men) who met these criteria. ECG, 24 hour blood pressure monitoring and two dimensional echocardiogram were obtained from all of the subjects participating in the study. Interleukin-10 (IL-10), interleukin-18 (IL-18), tumor necrosis factor alpha (TNF-α) and serum high-sensitivity C-reactive protein (hsCRP) concentrations were measured by using commercially available enzyme-linked immunosorbent assay method. Blood pressure variability was calculated as the within-subject standard deviation (SD) of blood pressure values obtained during the daytime, nighttime, and 24-hour periods. Blood pressure circadian variation is defined as the nocturnal decline in blood pressure. We investigated the association between inflammation and blood pressure, blood pressure variability and circadian variation. We found a linear correlation between night systolic and diastolic blood pressure variability and IL-18 concentrations. In other words, night systolic and diastolic blood pressure variability was found to be directly proportional to IL-18 concentrations. In addition, we found a linear relationship between IL-18 concentrations and daytime, nighttime, 24-hour blood pressure averages, left ventricular mass and left ventricular mass index, and a linear relationship between hsCRP and day, night, 24 hour systolic blood pressure, day and 24 hour pulse pressure. Interleukin-10 and TNF-α were found to be directly proportional to left ventricular mass and left ventricular mass index. We did not find any statistically significant association between blood pressure circadian variation and inflammation. However our findings suggest a relationship, further investigation is needed to clarify the association between blood pressure variability and inflammatory markers.