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Prehypertension causes a mounting problem of harmful cardiovascular disease risk in young adults

Carrington, Melinda

doi: 10.1097/HJH.0b013e328325d1a0
Editorial commentaries

Preventive Cardiology, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia

Correspondence to Dr Melinda Carrington, PhD, Postgrad Dip (Psych), BA, Preventive Cardiology, Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia Tel: +61 3 8532 1638; fax: +61 3 8532 1100

Globally, as nations become heavier and food choices become less nutritious, we are experiencing a mounting problem caused by the effects of suboptimal blood pressure (BP) (but not limited solely to this risk factor) on the development of cardiovascular disease (CVD) [1]. The outlook is bleak with the prevalence of hypertension predicted to increase to over 1.5 billion adults worldwide by 2025, up from one billion at the turn of the century [1]. Furthermore, the detrimental effects of elevated BP on heart health have been recognized in individuals with higher than recommended BP [2,3] yet who are not classified as hypertensive patients according to the WHO conventional cutoff of 140 mmHg systolic BP (SBP) or 90 mmHg diastolic BP (DBP).

The upshot of the awareness that raised BP is related to CVD at lower thresholds was influential in informing the decision to create a subcategory of BP in the 120–139 mmHg SBP and 80–89 mmHg DBP range, as contained in the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 7) [4]. Prior to this classification of ‘prehypertension’, individuals were identified with BP in the normal range (120–129 mmHg SBP and 80–84 mmHg DBP) or borderline range (130–139 mmHg SBP and 85–89 mmHg DBP) whereby levels were at the ‘upper end of normal’ or ‘high normal’. Redefining BP levels into a prehypertension category has good intentions, particularly in view of the global burden of disease attributable to BP [5]; it is designed to motivate the adoption of health promoting lifestyles and initiate effective strategies sooner to prevent the progression to hypertension and related CVD as early as possible. On the contrary, the concept has been criticized as an unnecessary definition of ‘nearly disease’, even in completely healthy individuals, and for not limiting the range to (borderline) individuals with high normal BP only [6].

Utilizing the JNC 7 classification of BP levels, Toprak et al. [7] in this edition highlight that prehypertension in young adults is associated with increased CVD risk and signs of subclinical CVD. The study is part of a wider longitudinal cohort survey, the Bogalusa Heart Study, and includes 1379 black and white adult men and women aged 20–44 years living in a semirural community in Bogalusa, Louisiana, USA.

The study by Toprak et al. [7] is interesting in several respects, the most important being the association of prehypertension with cardiovascular risk factors and adverse silent cardiac and vascular changes. Individuals with prehypertension had more harmful risk factors for overall cardiac and diabetic function, as evidenced by increased body fatness, pulse pressure and heart rate by SBP product; worse lipids and triglyceride profiles; higher glucose and insulin levels and more television time. Subclinical CVD, represented by key indicators of the left ventricle and common carotid artery intima–media thickness (CIMT), was also higher in young prehypertensive individuals. The prevalence of left ventricular hypertrophy and left ventricular dilatation was double in prehypertensive individuals as compared with normotensive individuals. Reportedly, these observations appear to show that prehypertension is nevertheless accompanied by signs of subclinical CVD as part of a progressive atherosclerotic process beginning in childhood and progressing across time [8] that can be detected before symptoms develop. This reaffirms the importance of the definition of prehypertension and yields evidence to refute the criticism that prehypertension resembles ‘nearly disease’ in potentially healthy individuals [6]. This is of special interest to health professionals and those engaged in primary prevention of CVD because the promotion of lifestyle changes or initiation of pharmacological treatment to prevent the further progression of CVD may be required earlier than usual [9]. Second, these main findings confirm that echocardiography and carotid ultrasonography are capable of detecting earlier systemic cardiovascular changes. CIMT measurement is a noninvasive, sensitive and well validated research tool for identifying and quantifying subclinical vascular disease and for evaluating CVD risk that has been translated increasingly into clinical practice [10]. On the contrary, the practicalities and cost benefit of echocardiography and carotid ultrasound based upon lower BP levels or even in routine screening for CVD may not be viable.

In Toprak et al.'s [7] article, there were key differentials according to sex and race in respect to the prevalence of prehypertension. High-risk subgroups included men and black young adults. Black women were more prehypertensive than white women, whereas the occurrence of prehypertension was similar in black and white men. By far sex, followed by BMI, were the strongest risk determinants of prehypertension in black and white adults. It should be noted however that the authors do not consider an evaluation of diet and lifestyle factors to assist with explaining key differences in the occurrence of prehypertension and related risk factors. A strong recommendation of the JNC 7 and indispensable part of the management of hypertension is diet, for assessing individuals' sodium intake as well as alcohol intake, and physical activity [4]. The contribution of lifestyle factors to sex and race differences in the prevalence of prehypertension will remain one question that the Toprak et al. [7] study will be unable to answer.

As the authors acknowledge, a limitation of the study was the determination of prehypertension on the basis of one occasion of BP measurements, albeit multiple readings were taken. Typically, a diagnosis of (pre)hypertension is required to be made upon consideration of multiple visits to a health professional. As such, the study findings may be overestimated because BP levels are generally higher due to environmental and situational effects. Nevertheless, the results are indicative, on the basis of a snapshot BP measure, of prehypertension in young adults being associated with increased CVD risk and signs of subclinical CVD. It follows that cause and effect cannot be revealed; the study design does not allow for determining whether the presence of adverse risk factors causes prehypertension or vice versa.

Despite these limitations, the study by Toprak et al. [7] is impressive not only for its size of nearly 1400 young adults within a large, population-based study, but for the advanced nature of the assessments in a sizeable cohort that utilize echocardiography and carotid ultrasonography. As indicated earlier, these are not routine measures to assess CVD risk but generally require a referral to be performed, after signs or symptoms of the disease are already present. The focus to include individuals approaching middle age is also a key target population; the critical period of time for men and women to be affected by CVD in their lifetime is middle age [3,11], and this age group is most likely to experience preventable hospital admissions and premature death in the next 20 years. Thus, prior to reaching middle age naturally represents the primary target for attempts to minimize the impact of suboptimal BP on cardiovascular health and diabetes. The prehypertension category is intended to identify these individuals in whom early interventions could reduce BP, decrease the rate of progression of BP to hypertensive levels with age or prevent hypertension entirely [4].

In conclusion, the key message in the study by Toprak et al. [7] is that CVD risk and signs of subclinical CVD is increased in young adults who are prehypertensive. Prehypertension and its associated adverse risk factors and cardiac and vascular changes exert a particularly strong impact on men and black young adults. This is important with the expanding waistlines of individuals worldwide creating a mounting problem for morbidity and mortality attributed to suboptimal BP. These results strongly support the need for healthy lifestyle modifications or, if necessary, recommendation of pharmacologic treatment in light of the extremely large proportion of young and middle-aged adults at risk of prehypertension.

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