By Dr. Colin Michie of AUC Medical School
Dr. Colin Michie has worked as a paediatrician in the United Kingdom, Africa, the Caribbean and the Middle East. He is specialised in nutrition, haematology and infectious diseases. Now the Associate Academic Dean for the American University of the Caribbean Medical School in St. Maarten, his enthusiasm is training medical students and healthcare teams to ensure they deliver better value health care.
It is tempting to imagine that a Caribbean island is an ideal home for a healthy heart. Here is physical beauty, lovely weather, great opportunities for relaxing and recharging. There is music, art, passionate and supportive communities. However, to accurately measure heart health, some risk factors need to be reviewed including one of the vital signs, blood pressure.
Blood pressures are often high on St. Maarten. A survey published two years ago following survey on the French side of the island showed this. Other studies from Saba, the Virgin Islands and Guadeloupe made similar findings: Raised blood pressure is a common problem in the Caribbean, just as it is in many other countries (it affects 32% of US adults). Nurses and doctors on this island, as well as our AUC community clinics find that many of those with high blood pressure have often not had regular check-ups and are not taking treatment. This Soualiga problem is something to look at closely because it is an indicator of how well we care for ourselves and each other. It deserves scrutiny by all of us because cardiovascular diseases are the most common cause of death.
Our blood pressures are not fixed. Pressures will increase if we sprint up a flight of stairs, they will fall when we go to sleep. Blood pressure will rise if we are irritated by a traffic jam or if we are frustrated. Part of the nervous system, the sympathetic or “fright and flight” nerves, ensures that should we meet a lion or wolf, we can escape efficiently. These days, this system is more likely to be activated by an argument with our siblings or a visit to the bank to ask for a loan.
The heart is a pump, pushing blood through elastic arteries into our tissues. If you are reading this sitting down, your heart will push out 5 litres of blood a minute; if you are on a treadmill in the gym, this can increase to 15. Your elastic arteries bounce and recoil with each heartbeat – this is the pulse you can feel in your wrist or ankles. Delivery of oxygen to your brain and muscles can be increased by the sympathetic nervous system dictating a higher blood pressure.
Normal measures of blood pressure are given in millimetres of mercury (mm Hg) because early measuring devices employed this heavy liquid. Some conversions may be helpful. 120 millimetres of mercury, a normal systolic blood pressure, is equivalent to just over 2.3 pounds per square inch (psi) or 16 kilopascals (kPa). There are two parts to blood pressure measurement. The lower resting pressure is the diastolic pressure. The higher systolic pressure is the result of the heart beating. The changes from diastolic to systolic with each heartbeat cause the blood to flow and deliver oxygen through the smallest blood vessels – the capillaries. Although muscles need extra blood to function at high output (those stairs again) at rest, it is your brain, heart and kidneys that use the most blood flow. The body detects its blood pressure using receptors named baroreceptors – found in both high pressure arteries and low pressure veins.
Technological advances allow us to check our own blood pressures: a wrist-band can give us an estimate of this measure as often as we want. This is a great advance because high blood pressure is silent. We probably will not know if it is there. If your systolic blood pressure is over 130 millimetres of mercury, you have high blood pressure or hypertension. Can this develop quickly? The answer is yes, particularly if you are young. Your blood pressure can move from being normal one year to hypertensive a year later. A normal blood pressure would be between 90/60 and 120/80. The kidneys that filter large volumes of blood are part of a hormonal system that is sensitive to blood volume. They make an enzyme renin that interacts with angiotensin. This interaction helps regulate blood volume. If the renin/angiotensin system becomes very active, blood pressure rises. Medications that reduce this activity are effective in reducing blood pressure.
Your heart is likely to beat between 100 and 200 000 times each year. If the heart beats at higher pressures, complications develop. The heart will become larger and demand more blood flow in its own blood vessels, the coronary arteries. Should heart muscle not receive sufficient oxygen, a heart attack will result: heart muscle cells can die. If heart muscle cells do not perform well, the heart will fail, causing fluid to accumulate in the lungs, legs and abdomen. At high pressures, all blood vessels may begin to malfunction, leading to vascular dementia, kidney failure, bleeds into the eye or erectile dysfunction. Large blood vessel damage includes dilation of the aorta (aortic aneurism). High blood pressure during pregnancy can be particularly dangerous to both mother and foetus.
As we become older, blood pressure tends to rise. This may be because of changes in the elastic tissues in the vascular tree. Other risk factors for high blood pressure include family history and race. In studies from the USA and the Caribbean, those of African descent in particular develop higher blood pressures at a younger age. Genetic investigations suggest more African individuals than those from other ethnicities are particularly sensitive to dietary salt. If genetically at risk, they will develop high blood pressures if they take over 4g (a teaspoon) of salt each day. This specific issue could be a particularly significant and ironic part of the Soualiga problem, given that this island provided so much salt to traders for several centuries.
There are other conditions that cause blood pressures to rise. High intakes of caffeine or alcohol as well as physical inactivity, being overweight, or having diabetes increase the risk of developing hypertension. The studies on St. Martin, Saba and in the USA suggest that living in poor socioeconomic conditions are also associated with hypertension. This can be a problem because everyone, wherever they live, needs to have their blood pressure checked regularly.
So if you have high blood pressure, two large questions follow: What can you do? And what can a medical service provide? As hypertension is a global problem, there are effective and well-tested recommendations that will reduce your blood pressure and its risks.
Self-help should come first and may be able to cure high blood pressure in some individuals. These strategies will improve the length and quality of our lives. Adopting a healthy diet with low salt and plenty of fruit and vegetables is an important start. Aim to eat five portions of fruit and vegetables each day, and less than a teaspoonful of salt. (The British Eatwell Guide is a useful ally to finding out details of this type of diet, as is the dietary guide to stop hypertension (DASH) found at: http://www.nhlbi.nih.gov/files/docs/public/heart/dash_brief.pdf). Johnny cakes, candy and fried foods need to take low priority to ensure you cut back on calories and harmful fats. Be careful about drinks too, avoiding high calorie drinks, particularly if they contain sugars or alcohol. Regular high alcohol intakes not only increase blood pressure but will add to the calories. Cutting back salt is never easy as salt is found in bread, cheese and in most hot spicy sauces.
Losing weight is important too for many islanders: It reduces the workload on your heart. Records of high blood pressure on St. Martin and Guadeloupe found that high blood pressure was often associated with abdominal obesity – a big waistline. This measurement is a rough estimate of fat inside the abdomen, a condition that needs to be reduced by all possible means.
To become healthy and have a lower blood pressure, physical activity should become a regular habit. Being active and taking regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. Regular exercise will help you lose weight, which will also help lower your blood pressure. Adults should do at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity such as cycling or fast walking every week. Physical activity can include sport, walking or gardening. This level of activity should also improve your sleep. Sleep problems are often linked to stress, anxiety and high blood pressure; they often improve with regular physical activity. It's a good idea to try to get at least six hours of sleep a night if you can. There are some good tips for getting to sleep on this British National Health Service website. Look too at last year’s December 7th Daily Herald. (https://www.thedailyherald.sx/supplements/health-beauty/71653-11-tips-to-beat-anxiety-and-get-some-sleep).
Although smoking doesn't cause high blood pressure, it does put you at a higher risk of a heart attack or a stroke. Smoking reduces oxygen available for our organs in many ways, as well as contributing to blood vessel damage so it is worthwhile stopping this.
Laurelle Richardson wrote in her poem – The Silk Tree: “Tamon trees around me is wha’ you drink for high blood pressure”. Tamarind, aloe vera, papaya, the periwinkle and sorrel have all long histories in the Caribbean as herbal treatments, usually as teas, for raised blood pressure. However, the evidence for these being good treatments is not strong. Bush teas may be useful, but they should never replace the strategies outlined above or prescribed medication.
A medical service will initially check your blood pressure on several occasions. If you have hypertension, depending on your background, a regular medication will probably be prescribed to keep your systolic blood pressure at 120 mmHg or less. Treatments often include diuretics that make you pass urine and reduce blood volume. There are medications that reduce activity in the renin-angiotensin system, including angiotensin converting enzyme inhibitors, renin inhibitors and blockers of the angiotensin receptors. Some treatments reduce the stress responses from the sympathetic nervous system (alpha and beta blockers) and the calcium channel blockers relax blood vessels. Novel approaches are being trialled of agents that can keep blood vessels more elastic as we age.
To maintain healthy hearts, each of us needs to examine our lifestyles carefully and have our blood pressures checked. Your health is important!
