Stroke and body mass index have been known to be related for at least a few decades, as the relationship of obesity and stroke became more and more clear in epidemiological studies. The mechanism that links stroke and obesity is the metabolic syndrome. In summary this is a clinical picture that happens when people eat and drink more than their metabolism is able to process. The result of the surplus is arterial hypertension due to excess salt; diabetes due to excess carbohydrates and sugar; dyslipidemia due to excess vegetal and animal fat. There are many measures of this state of obesity, but the most used is the body mass index, a simple calculation where you have: BMI=Height/Squared weight. Normal body mass index is between 18 and 25. Ideal is 22. Above 25 it is called overweight, and above 28 it is called obesity. People are refered to bariatric surgery, also called metabolic surgery, when body mass index is well above 32, or when they have complications of diabetes, hypertension and dyslipidemia.
One possible analogy for this to become more clear is that of a sawmill, or a lumbermill. Let us say it has a certain number of machines that saw trees, and transform them into wood slats. It is simple to imagine that they work at a certain speed, during certain times, and are able to process a certain number of trees. The capacity of this specific sawmill is very much like the metabolism of a person, which is carried out in a much more complex manner through the human organism. In case trucks bring more trees than the machines are able to process, the trees will accumulate. They may be placed in the parking lot, or reservoirs will need to be built to keep them. These reservoirs are the equivalent of the metabolic syndrome in people that become obese.
The metabolic syndrome includes high blood pressure, dyslipidemia and diabetes. It leads to many vascular complications, like aneurisms in various places, myocardial infarcts and various types of ischemia. The most feared are sudden cardiac death and stroke. The scientific novelty is that there was a hypothesis that the relationship of stroke to obesity had become less tight in recent times, due to the advances in detection and treatment of the complications.
This has now been proven scientifically. Investigators analyzed data from 13657 subjects in the Copenhagen City Heart Study, and 107040 in the Copenhagen General Population Study. They were randomly recruited in 1976-1978, and in 2003-2015. The Danish Patient Register and the Register of Causes of Death were used to detect stroke and outcome. The association decreased by 30% in body mass index and 30% in blood pressure in these 30 years. Body mass index was compared between > 30kg/m2 and 18-25kg/m2. Blood pressure was compared between >160/100 and <140/90. The changes were highly significant statistically (p=0.008 and p<0.001).
This means that the incidence of stroke can be decreased by 30% when people are treated with antihypertensive, antidiabetes and cholesterol- decreasing medication. This is good news, but of course it is more important to reduce intake and reduce body mass indez, as shown in other publications.
Dr Paulo Bittencourt