Interpreting readings
Systolic blood pressure is usually considered the more significant of the two values in a blood pressure reading, so someone with a blood pressure of 160/80mmHg is considered more at risk than with 150/90mmHg.7,8 If the systolic pressure is raised but diastolic pressure is normal or low, this is called isolated systolic hypertension (ISH).8
Blood pressure tends to increase with age due to physiological changes, with the large arteries becoming less flexible and atheroscleromas, or fatty plaques, building up.7 While high systolic blood pressure readings over the age of 50 are particularly suggestive of increased risk, some studies suggest that, under the age of 40, diastolic pressure is of more significance.8
Categorising high blood pressure
NICE clinical guideline CG127Â for diagnosing and managing hypertension describes three levels of hypertension:1
- Stage 1, where blood pressure measured in the clinic setting is 140/90mmHg or higher,
and readings from subsequent ambulatory blood pressure monitoring (ABPM), daytime average, or home blood pressure monitoring (HBPM), give an average of 135/85mmHg or higher - Stage 2 hypertension is a clinic blood pressure of 160/100mmHg or higher, with subsequent ABPM daytime average or HBPM average blood pressure readings of 150/95mmHg or higher
- Severe hypertension is where the clinic systolic blood pressure is 180mmHg or higher and/or clinic diastolic blood pressure is 110mmHg or higher. The American Heart Association (AHA) uses the term ‘hypertensive crisis’ for this level of high blood pressure, adding that emergency care is needed.7
NB NICE clinical guidance for hypertension in adults was being reviewed from October 2016, and its guidance on hypertension in pregnancy (CG107) will be reviewed in January 2017.1,9