Blood pressure is the force that circulating blood exerts against the walls of the arteries, written as two numbers in millimeters of mercury (mmHg): the systolic pressure while the heart contracts, over the diastolic pressure while it refills. A reading of 118/76 mmHg means a systolic of 118 and a diastolic of 76. It is the cheapest repeatable number in preventive medicine and one of the few you can measure properly at home. In most populations it drifts upward with age, so the trend matters more than any single reading.
What it measures
A cuff around the upper arm inflates until it stops flow in the brachial artery, then deflates while a monitor or clinician detects the pressure at which flow returns and the pressure at which it turns continuous again. The upper number, Systolic pressure (upper), reflects how hard the left ventricle pushes and how stiff the large arteries have become; the lower number reflects the pressure the system holds between beats. The gap between them is pulse pressure, which tends to widen after mid-life as arteries stiffen.
Technique moves the result more than most people expect. Sit quietly for about five minutes with your back supported, feet flat and the cuff at heart level; use a cuff sized to your arm; avoid caffeine, nicotine and exercise beforehand; and average two or three readings taken a minute apart. A cuff that is too small can shift a reading enough to change its category. Because a clinic visit itself raises pressure in some people, guidelines lean increasingly on home averages over several days or on 24-hour ambulatory monitoring.
Typical values
US guidelines from the American College of Cardiology and American Heart Association classify adult office readings as follows.
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | below 120 | and below 80 |
| Elevated | 120-129 | and below 80 |
| Hypertension, stage 1 | 130-139 | or 80-89 |
| Hypertension, stage 2 | 140 or higher | or 90 or higher |
These cut-offs are not universal. European guidelines have kept 140/90 mmHg as the threshold for diagnosing hypertension and label the band below it high-normal, so the same reading can be classified differently on either side of the Atlantic. Home and ambulatory averages use lower thresholds than office readings, because they exclude the clinic effect. Readings around 180/120 mmHg and above are handled as an emergency rather than as a category. A fuller breakdown of the categories and of correct home technique is set out in the reference entry Blood pressure (BP).
Why it matters for longevity
Blood pressure is one of the strongest and best-quantified risk markers we have. In large pooled analyses of observational cohorts, the association with death from stroke and heart disease runs continuously down to roughly 115/75 mmHg, with no clear point below which lower stops being better. Sustained elevation, or Arterial hypertension, is among the leading modifiable contributors to death and disability worldwide, and it damages more than the heart: it drives stroke, kidney decline and heart failure, and is linked in cohort data to later cognitive impairment and dementia.
Unlike most aging markers, this one has randomized evidence behind it. Treatment trials have reduced strokes, heart attacks and heart failure, and in high-risk adults more intensive lowering reduced cardiovascular events and all-cause mortality compared with standard targets. It is a number to act on, not just to watch.
What changes it
Several levers are genuinely under your control. Losing excess weight lowers pressure; so does cutting sodium, eating more potassium-rich plants in a DASH-style or Mediterranean pattern, limiting alcohol, and training regularly, with aerobic, isometric and strength work all showing reductions in trials. Short or poor sleep and untreated sleep apnea push pressure up. Once readings stay high, medication is the main lever, and several drug classes work well; which one suits you is a clinical decision. Some drivers you cannot change: arterial stiffening with age, family history, and kidney or hormonal conditions that raise pressure secondarily and need diagnosis rather than lifestyle work alone.
Related reading
- Heart Health: A Prevention Guide for Longevity
- Which Blood Tests Reflect Aging and How to Read Them
- How to Improve Metabolic Health: A Practical Guide
- Sauna and Heart Health: What the Research Shows
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.