New guidelines recommend using a less aggressive threshold for treating high blood pressure.
High blood pressure, or hypertension, is a common disease in which blood flows through the arteries at higher than normal pressures. It affects around 29 percent of adults in the United States.
Traditionally, the threshold for systolic blood pressure (the upper reading) above which doctors consider prescribing treatment has been 140 millimeters of mercury (mm Hg).
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, in order to reduce the risk of death, stroke, and cardiac events.
The two groups issued the new guideline 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 joint guideline and details of the evidence review are published online in Annals of Internal Medicine. A summary will also appear in the March/April 2017 issue of Annals of Family Medicine.
To arrive at the new guidelines, the groups carried out a systematic review of randomized controlled trials and observational studies. They looked for studies published from the start of database records to January 2015, and updated the list with a MEDLINE search up to September 2016.
They evaluated the evidence by analyzing 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.
‘Small benefit from additional aggressive treatment’
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.”
- Blood pressure normally rises with age and body size
- In the U.S., approximately 65 percent of adults aged 60 or above have high blood pressure
- It is more common in black U.S. adults than in those who are white or Hispanic.
The ACP and AAFP also point out 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.
High blood pressure damages blood vessels
Over time, consistently high blood pressure weakens and damages blood vessels, which can lead to complications, including heart disease, artery disease, heart attack, and stroke.
There are many risk factors for hypertension, some not modifiable (such as having a family history of high blood pressure) and some modifiable (for example, consuming too much salt and insufficient physical activity). Some medical conditions and medications may also increase blood pressure.
Blood pressure is measured at two points: when the heart beats (systolic pressure) and when the heart rests between beats (diastolic).
Conventionally, a blood pressure reading is expressed as millimeters of mercury, or mm Hg, with the systolic reading given first. Thus, a reading where the systolic pressure is 118 mm Hg and the diastolic is 76 mm Hg is given as 118/76 mm Hg, or “118 over 76.”
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. However, it can cause as much harm as hypertension when both numbers are too high.
“The most accurate measurements come from multiple blood pressure measurements made over time. These may include multiple measurements in clinical settings or ambulatory or home-monitoring.”