Hemodynamics and Na+ Storage in Salt-Sensitive Subjects (p 195)
Salt sensitivity (SS) of blood pressure (BP), the phenotype by which some humans exhibit BP responses parallel to their salt intake (SS) whereas others do not (salt resistant), is a risk factor for cardiovascular mortality independent of and as powerful as hypertension. The clinician should therefore be treating SS in hypertensive and perhaps normotensive subjects. This is not yet possible because diagnosis of SSBP requires complex protocols. Research on easier markers is far from reaching the clinic. Hence, clinicians may only make imperfect guesses based on clinical features of the phenotype. Also, developing specific therapies for SSBP requires thorough understanding of its mechanisms. Research has centered on defects in natriuresis that may expand plasma volume, leading to increases in vascular resistance via autoregulation of increased cardiac output, or on direct dysfunctional vascular responses to salt in SS. The study by Laffer et al shows that vascular responses to salt depletion differ between SS and salt-resistant subjects within 24 hours, without differences in cardiac output, findings consistent with direct effects of salt on the vasculature. Also, despite equal salt balance, SS and salt-resistant subjects handle water differently during salt loading and depletion (Figure). This is consistent with recently described associations between aging, hypertension, and nonisoosmolar salt storage in striated muscle and skin and also with newly recognized effects of hyperosmolar salt on immune cell activation. The study provides impetus for investigating mechanisms of a dysfunctional vascular response to salt in SSBP, which may lead to the development of specific therapies.
Exercise and Blood Pressure in Younger Adults (p 78)
A diagnosis of hypertension in early adulthood identifies someone with a high risk of cardiovascular events in later life. However, this diagnosis also offers an opportunity for earlier intervention to prevent accumulation of cardiac and vascular damage over the subsequent years. Current guidelines result in the majority of young people receiving lifestyle advice. A limitation of this guidance is that it is largely based on results from studies of adults aged >50 years or younger people who were not hypertensive. Physical activity behaviors and determinants vary considerably with age and disease. Therefore, we completed a systematic review and meta-analysis of randomized control trials that had evaluated exercise interventions in young adults with prehypertension or hypertension. Initial analysis supported an average 4 to 5 mm Hg reduction in both systolic and diastolic blood pressure related to exercise at 3- to 6-month follow-up. However, by 12-month follow-up, there was no longer a difference in blood pressure. Further analysis also highlighted that effective blood pressure reduction at 3 to 6 months had depended on high-intensity training and long contact time with an intervention team. This combined picture raises concern that current practice, to promote lifestyle intervention as first-line management, may be inadequately delivered and ultimately fail to manage the long-term risk of young adults presenting with elevated blood pressure.
Blood Pressure Variability and Cognitive Decline (p 106)
Vascular conditions such as hypertension are thought to be risk factors for cognitive decline, but randomized clinical trials of blood pressure (BP)–lowering treatments for reducing the risk of cognitive decline or dementia have largely failed to achieve beneficial effects. Over the past 6 years, scientific evidence has accumulated that BP variability over monthly or yearly visits may lead to greater risk of stroke and small and larger vessel cerebrovascular diseases. Using repeated measures of BP and cognitive function, the current prospective study shows that higher visit-to-visit variability in systolic BP, but not in mean BP, is associated with faster rate of cognitive decline in a general population of older adults (Figure). Higher diastolic BP variability between visits predicted faster cognitive decline only among adults aged 55 to 64 years, but not among adults aged ≥65 years. Our findings support the clinical relevance of BP variability between visits, which may not be a random phenomenon or simply an unimportant measurement artifact (eg, related to use of antihypertensive medication; timing of measures), but may instead provide information on pathological processes (eg, impaired endothelial function, inflammation) and be relevant for prognosis. Reducing the variability of BP may need to be considered in BP management for the benefits of cognitive health, but randomized clinical trials aimed at controlling BP instability to preserve cognitive function among older adults are needed.
- © 2016 American Heart Association, Inc.