Re: What causes high blood pressure?
Knowing nothing about you or your medical history, gender, age etc...it's difficult to know if your BP should be of any concern.
Was this one isolated reading?
Was it taken by a doctor?
Was it taken correctly?
Does it ever go higher?
Your diastolic (bottom #) is normal. The systolic (top #) @ 140 is mildly elevated and can be temporary.. due to stress, fear, pain, fatigue, salty foods, too much alcohol, caffeine, a million things.
Generally, regular areobic exercise (even a 30 min walk) on most days of the week is good for BP.
Also restricting your sodium intake to 2400mg a day (read labels!) is a good idea, although not all people are salt sensitive. Also don't add table salt to your meals. 2400mg of sodium is ONE TEASPOON SALT. Not much and hard to cut down to if you are a salt lover.
Alcohol in moderation.
Smoking is a no-no
Caffeine in moderation
If overweight, losing weight is the single most effective BP lowering modality there is (barring meds).
But again, 140/80 is not alarming at all, and unless you are getting the 140 consistently, I wouldn't worry too much. If you got this reading in a drug store, those machines can be inaccurate. If you are concerned, see your doctor.
Your sister's BP on the other hand, should be monitored over the course of a few months. A diastolic of 100 is too high. And it's important to ascertain whether her BP is sustained at this level at rest.... or if it was a temporary spike.