Sroke can be debilitating,  often devastating. Potentially reversible in some cases, it’s completely preventable in many more.

Hypertension, or high blood pressure, has long been known as a major cause of vascular disease including stroke. Indeed, dietary modification for treatment began early last century. In the 1980s, more Westerners became aware of the role of salt in hypertension. I remember vividly when the ‘Golden Arches’ fast food chain announced they were removing salt from their fries. I also remember they didn’t taste nearly as good! A few years later, salt was quietly reintroduced – now there’s a lesson in health marketing.

We need no reminding that hypertension costs billions of dollars globally and millions of lives are lost each year as a consequence of high blood pressure. Cambodia is no exception. A 2005 study estimated 12 percent of the population of Siem Reap and 25 percent of those in Kampong Cham had hypertension. Ninety-five percent of people with the condition have no identifiable disease process causing the rise in blood pressure. In this group high salt intake and being overweight are the two most common risk factors. It may be that a high-salt diet is the most common cause of hypertension in rural Cambodia. More work needs to be done, but these are alarming statistics.

Hypertension has an insidious course. In general, one’s blood pressure is related to one’s height and body mass. An extreme example is the giraffe, where the normal blood pressure is 240/160mmHg*. It takes a lot of pressure to maintain blood flow to a giraffe’s brain. On the other hand, small hibernating mammals maintain an average blood pressure of around 50mmHg. Humans are somewhere in between.

The number you’ll hear is 120/80. If you are a young small female, then no doubt your blood pressure will be 100/60 or perhaps lower, whereas a tall burly male would register much higher. Ideal blood pressure is less than 120/80. Treatment starts above 140/90 although if you are diabetic, the upper limit is 130/90.

Ideal blood pressure gives the optimum amount of blood flow to our organs so they are fully functional. Any more than this and the system gets stressed. The walls of our smaller arteries start to get sheared, damaged and eventually scarred. As they scar, they harden, further increasing blood pressure. The damage and scarring can lead to greater fragility. The small arteries supplying the kidney filtering system, the back of the eye and small brain vessels are the most vulnerable to permanent damage. Certainly mild kidney damage, poorer eyesight and mild cognitive decline are common in those with hypertension.

A recent study showed that for every 10mmHg increase in diastolic (but not systolic) blood pressure, the risk of cognitive impairment increased by 7 percent. Higher blood pressure can cause impairment of brain function at all ages, although older people are more at risk. Tiny little breakdowns in the walls of the smallest brain vessels eventually deprive brain cells of vital blood and oxygen and they die more rapidly. Early on, the effect of these tiny strokes isn’t noticed, but incrementally it adds up.

Although there is some evidence that treatment can reverse this impairment, study results are disappointingly mixed, so prevention remains the best cure for the brain.

The most unfortunate consequence of hypertension is a stroke. In many ways it is a matter of magnitude. A tiny stroke won’t be noticed, but if a larger vessel is affected, everything changes. The body is amazing good at regulating itself. On detection of a lack of oxygen to part of the brain, the body increases the blood pressure further to increase blood flow to the area. This can make the situation worse.

Depending on which part of the brain is affected, the effect will be different. A stroke on the left side means language is lost; on the right means being unable to perform tasks or movements despite understanding; the back of the brain affects eyesight. There are examples of stroke victims being unable to recognise faces, despite being able to see that it is a face. Oliver Sacks’ well-known 1985 book The Man Who Mistook His Wife for a Hat and Other Clinical Tales describes some of these weird and tragic stories. The most devastating strokes affect the brain stem (the centres of consciousness). Few survive such a devastating injury.

With some key excepptions, modern medicine has no effective treatment for stroke. In many cases watching, waiting, even hoping and praying are the only options. As a doctor it’s a tragic and often helpless situation. I often wish I had met the patient years before, perhaps warned them – but then I might see another younger patient who is blissfully ignorant of the debilitating consequences of not treating their high blood pressure.

Which brings us back to reality in Cambodia. How to explain these facts (and treatment) to a rural villager in Kampong Cham, let alone emphasise the risks to an exuberant expat immersed (or enmeshed) in the throngs of life in Phnom Penh? Eat less salt perhaps, but there’s no access to effective hypertensive treatment that can readily reverse this process. Ultimately greater development will bring better medical care, though accompanied by more medical problems, no doubt. For the rest of us, check your blood pressure regularly and if it’s too high then take the next step before it’s too late.

* mmHg is millimetres of mercury, the standard way of measuring blood pressure. The first number refers to systolic pressure (when the heart pumps) the second to diastolic blood pressure (in between pumps).