Traditionally, the threshold for systolic blood pressure (the upper reading) above which doctors consider prescribing treatment has been 140 millimetres of mercury (mm Hg).
In new data out this month in America, recommended levels are changing. The American College of Physicians (ACP) and the American Academy of Family Physicians (AAFP) now recommend that doctors start treatment in otherwise healthy adults aged 60 and older if their systolic blood pressure persistently reads 150 mm Hg or higher.
Treatment of blood pressure at these levels is done to reduce the risk of cardiac events, death and stroke.
Both medical groups issued the new guidelines following a review of the evidence on the benefits and harms of higher versus lower blood pressure thresholds for the treatment of hypertension in adults aged 60 and older. The guidelines have been published this month in Annals of Internal Medicine.
The new guidelines were arrived at through a systematic review of controlled trials and studies. They evaluated the evidence of deaths from all causes, together with illnesses, harms, and deaths linked to stroke and major cardiac events, including fatal and non-fatal heart attacks and sudden cardiac death.
There was not enough evidence to make recommendations about diastolic blood pressure targets in this guideline.
ACP president Nitin S. Damle says the evidence suggests that any additional benefit from aggressive treatment of high blood pressure is small, “with a lower magnitude of benefit and inconsistent results across outcomes.”
The ACP and AAFP point out when addressing the suggested change to levels that some patients may give falsely elevated readings because of the “white coat” effect – the fact they are in the clinic raises their blood pressure. It is therefore important for doctors to ensure that they have obtained an accurate blood pressure reading before starting or changing treatment.
The most accurate blood pressure readings come from measurements made over a period of time, either in the clinic or at home, they add.
The guidelines also contain two recommendations where the threshold target for systolic blood pressure should be 140 mm Hg. These concern when to consider initiating or intensifying drug therapy for patients aged 60 and older with certain histories or conditions.
This could be to reduce risk of recurrent stroke in patients with a history of stroke or transient ischemic attack (otherwise known as a ministroke) or, based on individual assessment, to reduce risk of stroke or cardiac events in some patients at high cardiovascular risk.
The ACP and AAFP note that people at higher cardiovascular risk includes all those with known vascular disease. They also include other groups, such as most patients with diabetes, some patients with chronic kidney disease, metabolic syndrome, and those of an older age.
They also advise that when prescribing drugs for high blood pressure, doctors should favor generic over brand-named as they have much the same effect but cost less, and patients are therefore more likely to keep using them as prescribed.
Blood pressure is measured at two points: when the heart beats (systolic pressure) and when the heart rests between beats (diastolic). This change affects the systolic pressure measurement.
In adults, normal blood pressure is defined as a systolic pressure below 120 mm Hg and a diastolic pressure below 80 mm Hg (120/80 mm Hg).
Abnormal blood pressure is defined as:
- Prehypertension: 120-139 mm Hg systolic or 80-89 diastolic mm Hg
- High blood pressure stage 1: 140-159 systolic or 90-99 diastolic
- High blood pressure stage 2: 160 or higher systolic or 100 or higher diastolic.
Many older adults have a condition called isolated systolic hypertension, where only systolic blood pressure is high.