Ben Basger takes a look at hypertension, its causes and the risks it poses
What do we know about hypertension in older people? We know that there is a marked increase in the prevalence of hypertension with aging. By age 70 years, approximately 65% of men and 75% of women have hypertension.
In older persons, hypertension is characterised by an increased systolic blood pressure with a normal or low diastolic blood pressure due to age-associated stiffening of the large arteries.
Hypertension is a potent risk factor for cardiovascular disease in the elderly. In older adults, hypertension is present in approximately 70% of patients with a myocardial infarction, 77% of patients with a stroke, 74% of patients with chronic heart failure and in approximately 30%–40% of patients with atrial fibrillation.
Hypertension is also a risk factor for sudden cardiac death, diabetes mellitus, the metabolic syndrome, chronic kidney disease, angina pectoris, peripheral arterial disease, vascular dementia, Alzheimer disease, left ventricular hypertrophy and ophthalmologic disorders (Am J Therapeutics 2014; 21: 436–437).
We know that there are substantial reductions in cardiovascular outcomes in persons aged 60–79 years treated with antihypertensive drug therapy and that blood pressure control rates remain suboptimal in the elderly; at age 70 years, approximately only one in three men and one in four women have adequate control of their blood pressure.
Nonpharmacologic lifestyle measures should be encouraged in older adults both to prevent development of hypertension and as adjunctive therapy in those with hypertension. These measures include sodium restriction, regular physical activity, weight control, smoking cessation, and avoidance of excessive alcohol intake.
It has been suggested that antihypertensive therapy be initiated in persons aged 65–79 years with a systolic blood pressure of 140 mm Hg or higher or a diastolic blood pressure of 90 mm Hg or higher and in persons aged 80 years and older with a systolic blood pressure of 150 mm Hg or higher. Initiation of antihypertensive drug therapy in the elderly should generally be at the lowest dose with gradual increments as tolerated (Am J Therapeutics 2014; 21: 436–437).
Why does blood pressure increase in so many with age? Factors responsible include an increase in arterial stiffness, with hypertrophy and loss of contractility of vascular smooth muscle cells and development of fibrosis; collagen deposition, fragmentation of elastic lamina and calcification; decreased baroreceptor sensitivity; increased sympathetic nervous system activity; increased a-adrenergic receptor responsiveness; endothelial dysfunction (decreased nitric oxide production); sodium sensitivity with decreased ability to excrete a sodium load; low plasma renin activity; insulin resistance and central adiposity.
Apart from a recommendation to allow higher systolic blood pressures in people older than 80 years because of this before beginning treatment, it has been recommended that patients with multiple comorbidities, frailty, and/or diminished functional or cognitive status may also be treated to a goal of less than 150/90 mm Hg (Med Clin N Am http://dx.doi.org/10.1016/j.mcna.2014.11.009).
This is because although all patients (including those over 75 years) treated to a lower target (a systolic BP of around 120 mmHg) have significantly fewer cardiovascular events and lower all-cause mortality compared to higher (around 135 mm Hg) targets, treatment-related adverse events increase in the more intensively treated patients, with more frequent hypotension, syncopal episodes, acute kidney injury and electrolyte abnormalities (MJA 2016; 205: 85-89).
It appears that initiation or intensity of treatment is based on considerations such as the degree of cardiovascular risk and tolerability of treatment.
Setting blood pressure targets appears to be a judgement call by someone who has all the relevant patient information.
Dr Ben Basger PhD MSc BPharm DipHPharm FPS AACPA is a clinical pharmacist and educator at Wolper Jewish Hospital and The University of Sydney, NSW.