My dog suffered a strange, worrying episode 2 weeks ago. His eyes started twitching wildly and his head drooped heavily to his left. It was also clear he was not quite conscious anymore and we drove him to the vet immediately.
The diagnosis was a haemorrhagic stroke in his brain and there is not much that can be done apart from putting him on some medication. But at least, we seemed to have caught it in time and we have some treatment options for him, though he is not quite the same as his head is now permanently turned to his left, which oddly makes him look even more cute.
As he is my top assistant when working and writing, the subject of strokes was worth investigating, as it was extremely disturbing to see one in action. My mother also suffered three strokes, two of which were very severe and the last one ended up finally causing her death.
Types of strokes
Not all strokes are the same, even though all strokes are effectively an attack event in the brain. There are three kinds of strokes:
1) an ischaemic stroke is caused by some blockage (e.g. a blood clot) cutting off the blood supply to parts of the brain. This is the most common type of stroke.
2) a haemorrhagic stroke is caused by a bleeding in or around the brain (e.g. when a blood vessel in the brain bursts or fails); and
3) a transient ischaemic attack (TIA), also known as a mini-stroke. It is the same as a stroke, except that the symptoms last only for a short period of time because the blockage stopping blood getting to the brain is only temporary.
Incidences of strokes
Every year around 800, 000 Americans suffer a stroke, and roughly 610, 000 of them are first-time occurrences. Also, approximately 160, 000 Americans die from stroke-related issues every year, which is roughly one in 20 deaths in the country.
The risk of strokes for men in the USA roughly doubles every decade of age from age 55 or so, where the 10-year probability is 5.9%, increasing to 11% at age 65 to over 22% at age 80 or more. For women in the USA, the 10-year probability is 3% at age 55, rising to 7.2% at age 65 and then 23.9% at age 80 or more.
The incidence of strokes in the USA is not typical of every country, but it does roughly match the statistics from many Westernised countries.
Risk factors
There are some unavoidable risk factors, such as age, gender, race, and a history of strokes in the family due to genetic factors. There may not be much one can do about such factors, but they may not be necessarily as dangerous as the avoidable lifestyle and dietary risk factors.
And most of these avoidable risk factors are related to the diet, apart from smoking and physical inactivity. So, in no particular order of importance, the dietary-related risk factors are normally:
• hypertension (high blood pressure)
• heart disease
• diabetes
• cholesterol imbalance
• obesity
The simple (and surprisingly often very difficult) solution for managing the above risk factors is to maintain a proper diet. That is because the dietary risk factors are related, in varying degrees.
A diet which helps reduce obesity also reduces heart disease, hypertension, cholesterol imbalances and may also ameliorate diabetes. Similarly, a diet to cope with heart disease will also help with the other risk factors. Looking at it another way, changing dietary habits to tackle any risk factor which may be of concern has the free benefit of reducing the risk in the other factors.
The optimal diet
I think by now most people would be aware that a better diet for health in general is one that incorporates five (80-90 grams) portions of fruits and vegetables daily with sensible proportions of good fats, proteins, fibre-rich foods, and meal quantities. And by now, most people would also have encountered probably hundreds of dietary suggestions, a certain proportion of which would have arisen from sponsored campaigns by food marketeers.
Therefore, I do not intend to offer advice, but instead review an interesting large-scale study into heart disease which curiously turned out to be one of the more intriguing studies into strokes.
A curious study
The 2013 ‘Prevención con Dieta Mediterránea’ (PREDIMED) study in Spain was the largest randomised controlled experiment examining the effects of a Mediterranean style diet ever conducted.
All 7, 447 participants in the study were aged between 55 to 80 years and selected because they were at high risk of cardiovascular disease (due to smoking, being overweight, obesity, hypertension, dyslipidemia (cholesterol imbalance), or a family history of heart disease).
The experiment was simple. One third of the participants were to have a Mediterranean diet supplemented with a litre of extra virgin olive oil (EVOO) every week, one third were on a Mediterranean diet augmented with a mix of nuts (15 grams walnuts, 7.5 grams almonds and 7.5 grams hazelnuts), and the final third control group was put on a low-fat control diet.
The study was stopped early because the results were too good.
After only 4.8 years, both the EVOO group (30%) and the nuts group (28%) had an average of 29% lower risk of heart disease than the control group. The explanation for this effect was investigated in some depth and the best theory was that it was due to compounds called polyphenols in EVOO and nuts. It appears that polyphenols might protect the cardiovascular system by improving the endothelial function and enhancing the endothelial synthesis of nitric oxide produced by digestion of EVOO and nuts.
Endothelial is the medical term related to the endothelium (the thin layer of cells that line the blood vessels, heart, and some body cavities), and nitric oxide promotes vascular dilation and protect blood vessels from damage due to platelets and cells circulating in blood.
A meta-analysis against other studies (covering 101, 460 people and 38, 673 stroke survivors) to validate the PREDIMED findings also found a strong correlation, and this meta-analysis additionally found that consumption of EVOO reduced the risk of strokes by 27%, which was a bonus result.
This close link between heart disease and strokes should not be unexpected; in short, what is good for cardiovascular conditions appears to be just as good for strokes, as mentioned earlier.
Other more in-depth analysis of the PREDIMED data found that people who consistently ate red and processed meats and other forms of typical junk foods were 48% more likely to have a cardiovascular event and 47% more likely to die. But remember, the people in the study all already had existing heart conditions, and many are past middle age. From this, the implication is people should avoid junk food and certain meats if they currently have a heart condition.
Although it is commonly perceived that fats are involved in strokes, there are curious anomalies in the stroke death rates in the world’s top fats consuming countries. For example, Belgium (95.0 grams), Germany (85.54 grams) and Malaysia (78.3 grams) are amongst the world’s top countries in daily fat consumption, but the rates of strokes are significantly different. Belgium has a stroke death rate of 7.94%, Germany 7.58% and yet Malaysia is 9.8%, over 2.3% higher than Belgium despite consuming almost 18% less fats.
To be fair, some of the difference in Malaysia is probably due to poorer health care systems, but there is also persistent evidence that the types of fats make a significant difference. Trans-fats are now banned for home consumption in much of the Western world but are often still sold in many tropical countries due to their ability to tolerate higher storage temperatures. Also, countries consuming mainly olive oil such as France and Spain have significantly lower stroke deaths despite having roughly the same fat intake as Malaysia.
Lifetime risk
An often-quoted paper called the Framingham Study in 2005 calculated the likely incidence of a stroke occurring within the lifespan of a US citizen. It turns out to be more than 1 chance in 6 for a middle-aged person, around the same for Alzheimer’s Disease. Interestingly, the study also estimated hypertension is the most significant factor determining the lifetime risk of getting a stroke. People with normal blood pressure had roughly half the risk of developing a stroke compared to people with high blood pressure (ie, >= 140/90 mm Hg).
My dog
As I started writing this, my dog appeared to have suffered a TIA (mini-stroke) this evening. He is resting now but it was a sobering reminder about the tissue-thin fragility of health. Less than three weeks ago, he was bounding around in the woods. Now we are watching him anxiously as he sleeps fitfully.
I do not know what the stroke risk factors are for dogs, but at least you should now have a better idea of what they are for people.
The views expressed here are entirely the writer’s own.
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