Masked hypertension and left ventricular structure and function in young black and white adults: the African-PREDICT study
Abstract
Motivation: Masked hypertension, a condition coined by Thomas Pickering, reflects a normal office and elevated out-of-office 24-h ambulatory blood pressure in untreated individuals. There are currently conflicting findings on the prevalence of masked hypertension between black and white ethnicities, and also between men and women. Most studies on masked hypertension have reported on elderly populations from Europe or the United States, or populations already diagnosed with cardiovascular disease. It is therefore imperative to seek better understanding of the frequency of masked hypertension in healthy young populations, but more importantly, to establish the possible effects of masked hypertension on subclinical organ damage. Although masked hypertension has been associated with left ventricular hypertrophy in the elderly, it is unknown if cardiac alterations are already present in young adults with masked hypertension. Masked hypertension might induce diastolic dysfunction, as shown in an elderly population. In addition, studies associating systolic dysfunction with masked hypertension are limited. Aim: The aim of this study was to determine whether masked hypertension in young adults associates with left ventricular structure and function in black and white participants of the African-PREDICT study. Methods: This study is affiliated with the larger African-PREDICT study (African Prospective study on Early Detection and Identification of Cardiovascular disease and hyperTension) conducted in and around the Potchefstroom area of the North West Province of South Africa. This cross-sectional study included 774 black and white men and women (aged 20-30 years) who had an office blood pressure <140/90 mmHg and no known cardiovascular disease, not taking any blood pressure medication, no chronic disease, human immunodeficiency virus uninfected and not pregnant or breastfeeding. Data with regards to age, sex and ethnicity was collected using a demographic and lifestyle questionnaire. Anthropometric measurements which included height, weight and waist circumference was obtained, we then calculated for body mass index (kg/m2) and body surface area. Cardiovascular measurements included office brachial blood pressure, 24-h ambulatory blood pressure and transthoracic echocardiography. Fasted venous blood samples were collected and basic serum analyses included creatinine, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, total cholesterol, triglycerides, glucose, y-glutamyl transferase and cotinine. The Chronic Kidney Disease Epidemiology Collaboration equation was used to estimate glomerular filtrate rate from serum creatinine. After no interaction was found for ethnicity and sex on the association between measures of left ventricular structure and function and masked hypertension, participants were stratified according to their masked hypertension status. T-tests and Chi-square tests were used to compare means and proportions between groups, respectively. Multivariable-adjusted logistic regression and multivariable-adjusted linear regression were used to investigate the relationship between left ventricular structure and function and masked hypertension. A p-value ≤0.05 was considered statistically significant. Results: When taking into account that we excluded participants with sustained and white-coat hypertension, overall, 16.4% of the young participants had MHT. The frequency of MHT was higher among young men (27.1%) than women and higher in whites (20.3%) than blacks. Higher left ventricular mass index was depicted in the masked hypertension group, both before (72.1 vs 80.9 g/m2, p<0.001) and after adjusting for age, sex and ethnicity (74.4 vs 78.6 g/m2, p=0.006). Masked hypertensives had a 1.67 [1.05—2.71 95% CI] times higher odds of having increased left ventricular mass index than normotensives, after adjustment for age, sex, ethnicity, socio-economic status, waist circumference, estimated glomerular filtrate rate, y-glutamyl transferase and cotinine. There were no significant odds of left ventricular dysfunction nor relative wall thickness found in these masked hypertensives. We further performed multivariable-adjusted linear regression analyses, and confirmed an independent positive association between left ventricular mass index and masked hypertension (adj. R2=0.193, β=0.08 [0.002; 0.16]; p=0.046). Conclusion: Elevated left ventricular mass index is eminent in young masked hypertensives and poses increased risk for future left ventricular hypertrophy and cardiovascular disease in these individuals. Therefore, a false negative diagnosis of hypertension based on only clinic blood pressure, not only underestimates the true prevalence of hypertension, but also increases the risk of cardiovascular morbidity and mortality in these under-diagnosed, untreated and unaware individuals, as they already present with early onset target organ damage.
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- Health Sciences [2060]