When it comes to blood pressure, low is always better. High blood pressure can stop the heart and trigger stroke is something we all know. A study from Boston University now shows it also damages memory and causes attention deficits and dementia as you get older.
High blood pressure (hypertension) in your '50s can trigger memory lapses in later years and lead to a decline in brain function, reported researchers in the Journal of Alzheimer's Disease (http://bit.ly/1StyZ0l) on Friday.
Using data from the ongoing Framingham Heart Study that began in 1948, Boston University School of Medicine researchers measured the blood pressure of 378 people when they were between 50 and 60 years old, and then tested their brain function roughly 30 years later when they were 80 years or older. People with high blood pressure at midlife did a lot worse on tests of attention, working memory, mental flexibility and self-control than people with healthy blood pressure in their 50s.
How low is too low
The risk of disease and death doubles with each 20-point rise in the higher number (systolic pressure measured when the heart pumps out blood), or a 10-point rise in the lower number (diastolic pressure measured while the heart is being refilled between beats).
Several studies over the past decade show that the risk of heart disease begins at blood pressures lower than previously thought. Normal blood pressure is 120 /80 mmHg or lower, and as long as you don't feel faint or dizzy, the lower it is, the more benefits it brings. People who are lean and very active often have blood pressures of 110/70 mmHg.
A single lower-than-normal reading is not a cause for worry if there are no symptoms, says the American Heart Association. But a sudden drop in pressure - a fall of 20/10 mmHg or more - along with symptoms of dizziness, fainting spells, clammy skin, nausea, blurred vision or disorientation indicate trouble.
"Isolated fall in blood pressure without symptoms is not a problem, but if you have low blood pressure accompanied with chest pain, treat it like a medical emergency as it could be an ongoing heart attack," says Dr R R Kasliwal, chairman, clinical and preventive cardiology, Medanta, Gurgaon.
A sharp fall in blood pressure may be temporary, with even mild dehydration - a loss of 1-2% of the body weight - caused by fever, vomiting, diarrhoea, sweating in the heat or overuse of diuretics causing it to drop.
You blood pressure readings may vary within a short period - sometimes from one heartbeat to the next. Among the factors that affect readings are your breathing rhythm, stress levels, physical condition, hydration level. It also depends on the time of day, with blood pressure usually being the lowest at night and rising sharply when you wake up.
Uncontrolled bleeding, severe infection, an acute allergic reaction, pregnancy, suddenly standing up (chronic orthostatic hypertension within three minutes of standing caused when the hear cannot correctly regulate normal pooling of the blood in your legs from prolonged sitting or lying down), uncontrolled diabetes, heart disease and excessive sweating may also cause sudden fall in blood pressure. Chronic orthostatic hypertension affects 5-11% people in midlife and one in four silts after age 65.
Medicines such as beta-blockers, calcium-channel blockers and ACE inhibitors prescribed for heart disorders, diuretics, antipsychotics, anti-depressants and drugs for Parkinson's disease also make blood pressure fall.
Wearing compression stockings -- tight-fitting socks or tights - during long flights or situations when you're forced to sit for long spells help by providing extra pressure to your feet, legs and stomach to improve circulation and increases blood pressure.
For people prone to low blood pressure, cutting back on caffeine and alcohol helps by preventing dehydration. Eating small, frequent meals prevents postprandial hypotension (low blood pressure after eating), as does sitting still for a few minutes after a meal.
People with low blood pressure are usually not prescribed drugs to raise it since treating the underlying cause is usually all the treatment needed. If low blood pressure is persistent, fludrocortisones - a corticosteroid that makes the kidneys retain sodium -- are prescribed. Another medicine prescribed is midodrine, which restricts blood vessels and raises blood pressure in people with chronic orthostatic hypotension.