Hypertension and Neurocognitive Function in Older Adults: Blood Pressure and Beyond

Article excerpt

ABSTRACT

Among middle-aged to older adults in the United States, the cumulative lifetime incidence of hypertension is 90%. Hypertension confers risk for stroke, vascular dementia, and Alzheimer's disease. Prior to stroke or dementia, hypertension and both high and low levels of blood pressure (BP) are associated with poorer performance across multiple domains of neurocognitive function and decline. Several vulnerability and resilience factors have been noted and multiple underlying biological mechanisms are suggested. Complicating the study of hypertension-cognition relations are the respective influences of correlated cardiovascular risk factors, BP reactivity, arterial stiffening, and other dimensions of subclinical vascular disease. It is possible that multiple treatment targets are needed to preserve brain and cognitive function among those with hypertension.

INTRODUCTION

Hypertension affects approximately one third of adults in the United States (Chobanian et al., 2003). Among middle-aged to older adults, the cumulative lifetime incidence of hypertension is a staggering 90% (Franklin et al., 2001). Hypertension confers substantially increased risk for stroke (Rosamond et al., 2008) and is associated with the development of both vascular dementia and Alzheimer's disease (AD; Skoog & Gustafson, 2006). Furthermore, recent research suggests that the patterns of cognitive impairment associated with vascular dementia and AD are not entirely distinct (de la Torre, 2004; Román, 2001; White & Launer, 2006) and that most dementia is likely "mixed" with involvement of both vascular and neurodegenerative pathology (Korczyn & Vakhapova, 2007; Román, 2002).

Outside the context of clinical stroke or dementia, the brain remains an under-recognized target organ of hypertension. Yet, long before such overt and devastating clinical manifestations, hypertension has a known, negative impact on the brain and neurocognitive function in cohorts ranging from children to the elderly (Waldstein, Wendell, Hosey, Seliger, & Katzel, in press). Accordingly, a life span approach to the study of hypertension and neurocognition is clearly warranted.

Here, we provide an overview of the relations of blood pressure (BP) or hypertension to neurocognitive function with a focus on older adults. We seek to offer breadth rather than depth of coverage and we highlight positive associations for ease of presentation. We first briefly review issues related to the definition of hypertension and its age-related pathophysiology, measurement, and treatment. Next, we examine relations of hypertension and BP to neurocognitive function, followed by a discussion of relevant effect modifiers and biological mediators. We then step beyond BP to discuss several risk factors known to aggregate with hypertension including components of the metabolic syndrome and stress-induced BP reactivity. We conclude with consideration of several aspects of subclinical vascular disease with known relations to hypertension, including arterial stiffening, left ventricular hypertrophy, and carotid intimal-medial thickening.

DEFINITION, PREVALENCE, AND AWARENESS OF HYPERTENSION

Hypertension, an elevation in BP that places individuals at increased risk for end-organ damage in a number of vascular beds including the heart, brain, kidneys, retina, and large conduit arteries, is the most common risk factor for cardiovascular disease (CVD; Lloyd-Jones et al., 2010). The diagnostic criteria for hypertension continue to evolve. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure ONC VII) defined and classified hypertension in adults as a systolic BP > 140 mm Hg, diastolic BP > 90 mm Hg, taking antihypertensive medicine, or the patient having been told at least twice by a physician or other health professional that one has hypertension (Chobanian et al., 2003). …