Hypertension in Older People

Older patients represent the most rapidly increasing segment of the United States population and account for the largest health care expenditures. Age is a major risk factor for the development of hypertension, and in particular, systolic hypertension. From 1999 to 2000, approximately 10 million men over the age of 65 and at least 17 million women over the same age had hypertension. From 2003 to 2006, 65.4% of men and 70.8% of women aged 65 to 74 had hypertension, whereas for ages 75 and above, the prevalence was 64.6% for men and 77.3% for women. Within the hypertensive population, African Americans and Latino Americans of all ages, including older patients, exhibit higher rates of hypertension.

The increased prevalence of hypertension is mainly the result of the aging of the population, in particular the very old (≥80 years of age). Over the last 40 years, this population group has expanded exponentially. Currently, life expectancy for these individuals living in the Organization for Economic Cooperation and Development (OECD) group of countries is approximately 9 years compared with about 6 years in the 1970s, representing an increase of 50%. The number of people in the U.S. over 85 years of age is expected to increase to 16 million compared with 5.7 million in 2010. In terms of incidence of hypertension, there has been little change in the percentage of patients over the age of 60 years who have hypertension. However, as more people survive into their later years, the absolute number of individuals with hypertension constantly increases. Observational data from the Framingham Heart Study suggest that the lifetime risk of developing hypertension is greater than 90% for an American 55 to 65 years of age. However, the continuously increasing number of older people, especially in the over-80 age group, also leads to a growing population with high blood pressure and at the same time more prone to multimorbidity, frailty, cognitive decline, polypharmacy, and partial or complete loss of autonomy.

High blood pressure (BP), in particular systolic hypertension, is a clinical expression of arterial stiffness developing during the aging process. In the past, the increase in systolic blood pressure (SBP) and pulse pressure (PP) was considered part of the normal aging process and was therefore deemed not to require therapeutic intervention. However, older subjects with higher SBP and PP levels not only have higher cardiovascular morbidity and mortality but also exhibit a higher prevalence of other age-related diseases, loss of autonomy, and shorter life expectancy. Importantly, several studies have also shown that the risk of neurocognitive disorders, both Alzheimer and vascular types, may be associated with elevated BP. As described in the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 7), the association between cardiovascular (CV) events and hypertension is linear, graded, and continuous: the higher the BP, the higher the CV risk.

This dogma, that is, the association between SBP and morbidity and mortality, may not be valid however in very old frail individuals with several comorbidities. In these subjects, low SBP levels may ultimately not signify a sign of so-called “good arterial health” but more often of malnutrition and of comorbidities such as heart failure, neurological disorders, and so on, as well as other concomitant conditions associated with poor prognosis. Therefore, information provided by SBP measurements in predicting cardiovascular risk may be misleading. Currently, the majority of evidence regarding the risks of high BP as well as the benefits from its correction are derived from a simple extrapolation of data obtained in younger populations and in well-selected robust older individuals.

These findings show that the general term “hypertension in the elderly” is not sufficiently accurate because it amalgamates “younger” old patients (60 to 70 years of age) with the oldest old and that the management of hypertension in individuals aged 80 years and older should be specifically and separately addressed. Although this age-threshold is arbitrary, there are two major differences between these two age groups: (1) the incidence and prevalence of comorbidities, frailty, and loss of autonomy greatly increases after the age of 80 years ; and (2) in the “younger” old patients, there is solid evidence regarding the management of hypertension and the benefits of reducing blood pressure, whereas there is limited evidence in patients over 80 years especially in those with frailty, cognitive impairment, and loss of autonomy.

Therefore, the management of older patients with high blood pressure must take into account two major differences compared with younger hypertensive subjects:

1.
Presence of isolated or predominant systolic hypertension as a result of arterial aging
2.
Presence of frailty, multimorbidity, polymedication, and loss of autonomy

Increase in Systolic Blood Pressure in Older Adults: a Consequence of the Arterial Aging

Whereas both SBP and diastolic blood pressure (DBP) are independently predictive of cardiovascular disease (CVD) risk in individuals younger than 50 years of age, epidemiological data demonstrate that SBP is a stronger predictor of risk and that DBP is inversely associated with risk for those aged 50 years and older. Although this observation was originally made almost 4 decades ago, it was not included in U.S. guidelines until 1993, when the Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNC V) recognized isolated systolic hypertension (ISH) as an important marker of CVD risk. The staging of hypertension in older individuals is usually closely related to SBP. Upon analysis of the Framingham Heart Study, knowledge of only SBP correctly classified the stage of hypertension in 99% of patients over 60 years of age.

The Reasons for the Increase in Pulse Pressure With Age

Until the age of 50 to 60 years, both SBP and DBP increase as individual get older. Thereafter, in the majority of cases, SBP increases with age disproportionally to DBP. The most common cause for the disruption of the correlation between SBP and DBP (leading to an excessive increase in SBP and PP) is the progressive stiffening of the arterial wall. Indeed, arterial stiffness develops as a consequence of several structural and functional changes in large arteries. Wall hypertrophy, calcium deposits, and changes in the extracellular matrix, including an increase in collagen and fibronectin, fragmentation and disorganization of the elastin network, nonenzymatic crosslinks, and cell-matrix interactions, are the predominant structural determinants of the decrease in elastic properties and the development of large artery stiffness.

It is important to point out at this juncture that SBP is dependent on left ventricular performance and on the stiffness of the aorta and other large arteries. Thus, peak systolic pressure will be greater if the arterial wall is more rigid. On the other hand, after closure of the aortic valves, arterial pressure gradually falls as blood is drained toward the peripheral vascular networks. Minimum DBP is determined by the duration of the diastolic interval and the rate at which pressure falls. The rate of drop in pressure is influenced by the rate of outflow, that is, peripheral resistance, and by viscoelastic arterial properties. Hence, at a given vascular resistance, the drop in diastolic pressure will be greater if the rigidity of large arteries is increased. The viscoelastic properties of arterial walls are also a determinant of the speed of propagation of the arterial pressure wave (pulse wave velocity-PWV) and of the timing of wave reflections. Stiffening of the arteries increases PWV and may be responsible for an earlier return of the reflected waves, which overlap the incident pressure wave, thus further contributing to the increase in SBP and PP. Several cross-sectional and longitudinal clinical studies have shown that the increase in arterial stiffness with age is not linear, being more pronounced after the age of 55 to 60 years, which may in turn explain the more pronounced increase in PP after this age. In addition to age, any disease and/or condition that induces an accelerated increase in arterial stiffness will be clinically expressed by an increase in SBP and PP. Diabetes is a typical example of accelerated arterial aging leading to a more noticeable increase in PP with age as compared with nondiabetic patients because of a more pronounced increase in arterial stiffness. In accordance with this concept, increased PP with age is more pronounced in diabetics with initial microalbuminuria or macroalbuminuria and retinopathy, suggesting that the progression in arterial aging is more prominent in the presence of target organ damage.

The Increasing Impact of Systolic/Pulse Pressure in Older Adults

The above considerations offer a better explanation as to why SBP and PP better reflect CVD risk in older subjects, whereas DBP better reflects the risk in younger subjects. Indeed, DBP in young patients is predominantly dependent on peripheral resistance and therefore low DBP reflects low peripheral resistance. In addition, in younger subjects with hyperkinetic circulation, DBP is less variable than SBP, thus better reflecting cardiovascular risk. In older subjects, a low DBP may reflect high arterial stiffness, which is a major manifestation of arterial aging rather than low peripheral resistance. In this instance, low DBP is associated with high SBP and high PP as well as increased cardiovascular risk.

Furthermore, in 2003, the European guidelines on the management of hypertension suggested for the first time that PP may represent an independent risk factor, and that therapeutic studies should henceforth be conducted to assess the benefits of reducing PP in terms of cardiovascular morbidity and mortality, especially amongst those over 60 years of age. Indeed, since the first study conducted in 1989 which demonstrated a positive association between PP and target organ damage, a large number of clinical studies, particularly over the past 10 years, have notably shown that increased PP is a strong predictor of coronary disease, incidence of heart failure and cardiovascular morbidity and mortality, independently of mean BP levels. Such observations have been made in a number of varied populations although they appear to be more pronounced in diabetics and older subjects. Threshold PP risk values have since been proposed, notably a value of approximately 65 mm Hg. This association between PP and CV mortality has essentially been observed in older patients enrolled in large clinical trials, as shown in a meta-analysis published in 2002 during which seven clinical trials in older adults were analyzed (EWPHE, HEP, MRC1, MRC2, SHEP, STOP, Syst-Eur). The subjects enrolled in these trials were older patients with systolic-diastolic hypertension or isolated systolic hypertension.

Frailty, Multimorbidity, Polypharmacy, and Loss of Autonomy

Frailty is a “biological syndrome of decreased reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems and causing vulnerability to adverse outcomes.” Frailty dramatically increases after the age of 80 years; however chronological age is only one of the factors predicting frailty. Susceptibility to stressors is also influenced by biological, behavioral, environmental, and social risk factors, consequently resulting in an increased risk of multiple adverse health outcomes, including disability, morbidity, falls, hospitalization, institutionalization, and death. A standardized frailty phenotype was articulated in 2001 by Linda Fried and colleagues, suggesting that with very simple tests and questions, one could identify frail individuals by the presence of three or more of the following criteria: unintended weight loss, self-reported exhaustion, weakness, slow walking speed, and low physical activity. In 2008, Bergman extended the Fried definition using a life-course approach, which incorporates biological, social, clinical, psychological, and environmental determinants. Bergman’s definition thus identified seven markers of frailty: nutrition, mobility, activity, strength, endurance, cognition, and mood.

Of particular note, recent clinical studies have shown a substantial influence of frailty status on the relationship between BP and outcomes, especially in old treated hypertensive individuals : thus in the absence of major frailty assessed by various means (low walking speed, altered cognition, loss of autonomy), the higher the SBP, the higher the risk of mortality whereas in those with major signs of frailty, SBP was negatively associated with risk of death. Recent studies have shown that the increased morbidity and mortality in very old frail subjects were mainly observed in treated hypertensives and not in normotensive individuals especially in those receiving several antihypertensive drugs. These findings are mainly attributed to the fact that in older individuals, low BP levels are often associated with several comorbidities, which predispose to a decreased perfusion of target organs and higher mortality risk.

Also, polypharmacy (generally defined as taking more than four drugs) and drug-related adverse effects are major issues in this population and may additionally contribute to morbidity, higher rates of hospitalizations, and mortality. Polypharmacy is common among frail older adults, with the age group between 75 and 84 years recording the highest intake, that is, between five and nine drugs per day in more than 50% of patients. Polypharmacy increases the risk of drug-drug interactions, adverse drug events, and the possibility of a prescribing cascade. The risk of adverse drug-drug interactions is strongly related to the number of drugs taken, varying from less than 15% in those taking two or less drugs to more than 80% in those taking seven or more drugs per day. Changes in pharmacokinetics and pharmacodynamics during the aging process, and in particular reduced renal clearance, reduced hepatic metabolism, a decline in cardiac output as well as a decrease in lean mass and total body water, can modify drug pharmacokinetics and contribute to the increased risk of adverse drug reactions. Moreover, a decline in serum albumin attributed to acute illness or malnutrition may additionally result in transformed free-drug accumulation. Likewise, reduced homeostatic mechanisms render older persons more vulnerable to adverse effects (e.g., orthostatic hypotension is more likely to occur at a ‘usual dose’ of a vasodilating drug in an older person, based on a slow baroreceptor response).

Antihypertensive medications are often involved in adverse drug events and related hospitalizations. Several methods and tools have been developed to assess medication appropriateness. Explicit instruments, in particular the Beers list in the U.S. and the STOPP/START criteria in Europe, are increasingly used, either as a tool applied by various multidisciplinary geriatric teams or within a comprehensive geriatric assessment. These instruments are primarily useful to identify risks that might require further intervention, although they can never substitute for global clinical judgment of each older patient.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here