Normotensive aging: finally, an ‘iron in the fire’

Systemic hypertension is still reigning the world as an evil emperor. Despite much scientific progress, the entire empire is colonized by many people with elevated blood pressure, a risk factor for increased morbidity and premature mortality. A persistent increase in blood pressure leads to target organ damage, which portends to decreased survival and shortens life expectancy. Therefore, it is prudent to aim for ‘normal’ blood pressure levels in the population. Although a precise cause of hypertension remains elusive, aging is associated with a progressive elevation in blood pressure levels accompanied by cardiovascular and cerebrovascular diseases. In the study reported in this issue [1], the authors while documenting a correlation between age and blood pressure levels in 3.3 million Chinese adults, report a wide variation in the incidence of hypertension across some subgroups and noted that antihypertensive therapy prevents age-related increases in blood pressure levels. These findings have profound implications for population science and heterogeneity of exposure to high blood pressure in certain segments of society; this cross-sectional study identified groups with steep and not-so-steep increases in blood pressure with advancing age. Age influences the blood pressure levels both in normotensive and hypertensive participants [2,3]. Although the observations noted in the study by Caraballo and colleagues are cross-sectional with no follow-up, certain factors, such as sex, lower socioeconomic status (SES), a rural environment and living at altitude, favoured higher levels of blood pressure. Some studies have inferred that hypertension is an unavoidable consequence of aging. With advancing age, large arteries become stiff and propagate early reflected pulse pressure waves, which increase the myocardial workload and unmask myocardial ischaemia. Although peripheral vascular resistance may initiate hypertension, it is the acceleration of large artery stiffness, which promotes systolic hypertension. Age-related changes in pressor or humoral mechanisms, growth factors and cytokines, participate in the pathogenesis of hypertension in the elderly. Left ventricular hypertrophy (LVH), a marker of prolonged hypertension in the elderly is largely because of increased vascular impedance and consequent myocyte growth. Cardiac index and heart rate decrease with aging. These hemodynamic alterations and adaptive changes should be kept in mind while choosing pharmacological therapy to treat hypertension in the elderly. The authors noted that chronic antihypertensive therapy blunted the age-related occurrence of hypertension, confirming smaller previous studies, which demonstrated that hypertension can be prevented by antihypertensive drug therapy [4,5]. It is unclear whether any specific pharmacological class of drugs offers an advantage in the blood pressure-lowering strategies for the elderly. The question often raised is whether the elderly can tolerate blood pressure reduction with antihypertensive drugs. This question was well addressed by various studies including SPRINT [6–8], which showed that not only is drug therapy well tolerated by the elderly but hypertension-related complications are significantly reduced. Hence, a new viewpoint is presented to the global community --- age-related hypertension and its sequelae can be prevented by antihypertensive drug therapy! Women were shown to have a greater prevalence of hypertension compared with men. The basis for this observation is likely complex because of other confounding factors in addition to sex. Is it possible that women are also subjected to socioeconomic stress and lower educational status? Postmenopausal hypertension increases the cardiovascular risk and hence needs closer attention. Further research is required to discover sex-related differences in blood pressure regulation, such as humoral mechanisms, lack of nocturnal drop in blood pressure, and oxidative stress. As women derive the same benefit as men from the treatment of hypertension, society should consider the former as a ‘high risk’ category endorsing aggressive blood pressure-reduction goals. A lower SES has been identified in many studies as a contributing factor for hypertension [9,10]. This is a complex issue as economic status is not a stand-alone exclusive phenomenon disconnected from educational level and rural living, and so forth. SES can also be linked to other pressor mechanisms -- sedentary lifestyle, physical, and emotional violence, tobacco and alcohol consumption and unhealthy diets, lending further support to the ‘Mosaic’ hypothesis of hypertension. A possible association between high altitude and high blood pressure, a much-debated conjecture, was also noted in this study. Tibet, often referred to as the ‘Third Pole’ (because of its high altitude) is known for reduced life expectancy compared with other regions of China; hypertension may be a possible underlying factor but no clear-cut evidence is presented. Chronic hypoxaemia triggers various chemoreceptor-sensitive pressor mechanisms. It is not known whether migration to a lower altitude is beneficial. Further, there are other influencing factors at high altitude -- lower SES, civic challenges, food insecurity and access to healthcare, and so forth. However, suffice it to acknowledge that high altitude living is a potential drawback to the maintenance of good health. The burden of cardiovascular disease (CVD) continues to increase at alarming pace globally and hence population aging requires health systems to prioritize geriatric public health. Certain subpopulations (e.g. the elderly and women) exposed to susceptible disease, require focused delivery of preventive methods for the high-risk groups [11,12]. We must energize global efforts to prevent suffering and premature death caused by CVD. Health policy avenues tend to be complex and at times dictated by political expediency but we should implement effective, affordable and sustainable strategies for high-risk groups, such as the elderly. We can assume that chronological age is not a good surrogate for biological age. Broader and earlier introduction of antihypertensive drug therapy may flatten the age-related rise in blood pressure. Additional studies should expand and explore this readily available pharmacological approach. Normotensive aging is possible but whether pre-emptive antihypertensive drug therapy is a categorical option for public health policy should be fully probed. As blood pressure elevation may be inescapable with advancing age, it is preferable ‘to stop the train in its tracks’ before it meets with a disaster. Although little can be done to alter geographic and gender attributes of blood pressure regulation, public health policies should consider socioeconomic and educational factors for preventive and corrective measures. Aging is inevitable, but hypertension is preventable. ACKNOWLEDGEMENTS Conflicts of interest There are no conflicts of interest.