The Risk Factors of Strokes
By Patrick Stiles
Strokes are a very serious issue. According to the CDC, an American dies of a stroke every 4 minutes (Stroke Facts). There are three main types of strokes. Ischemic strokes, which is what most strokes are, are what "happens when blood flow through the artery that supplies oxygen-rich blood to the brain becomes blocked." Hemorrhagic strokes, which are either intracerebral or subarachnoid, are what "happens when an artery in the brain leaks blood or ruptures." Transient Ischemic Attacks, or "mini-strokes," are when "blood to the brain is blocked for only a short time—usually no more than 5 minutes," and is a warning of a potential, more serious, future stroke (Types of Strokes). While stroke deaths will unfortunately remain high for the foreseeable future, they can still be reduced. The purpose of this page is to help understand the major known causes of strokes. Please note that this page is not comprehensive.
For the models, the different colors represent different things:
Yellow represents the confluence of all the different factors, the main focus of this page. In this case, it represents the risk of dying from a stroke
Red represents dependent factors (things that are influenced by other things)
Purple represents independent factors that individuals have little control over
Blue represents independent factors that individuals can change. This is arguably the most important color to pay attention to
This project uses Loopy, which is very easy to learn.
Risk of Dying
The risk of dying from a stroke is influenced both by the risk of getting a stroke and the treatment received. Both of these factors are able to be greatly affected by human behavior, as will be detailed further on.
Risk of Stroke
The risk of getting a stroke is influenced by cholesterol, family history, the effect of smoking, air pollution, the use of illicit substances, diabetes, atrial cardiopathy, atrial fibrillation, fat, hypertension, stress, alcohol consumption, and the effect of infection. One's family history of strokes is a major factor. There is not one "stroke gene" that increases the likelihood of a stroke, rather there are many gene disorders that may do so, either directly or by increasing the likelihood of one of the causes of strokes, such as atrial fibrillation. A history of stroke in an individual's family can increase their risk of stroke by 30%. In 2011, "124 million people in the United States were living in areas that did not meet the United States Environmental Protection Agency (EPA) National Ambient Air Quality Standards." Being exposed to air pollution long term is a risk factor for strokes, but there is less that can be done about this at an individual level given how harmful air quality is a widespread problem. Using drugs like "cocaine, heroin, amphetamines, and ecstasy" can also contribute to an increased chance of having a stroke. While research is still being done on this topic, atrial cardiopathy has been found to be an independent risk factor for strokes, as well as a cause for atrial fibrillation. Stress has also been identified as a short-term trigger for ischemic strokes, different from longer-term risk factors like hypertension and hyperlipidemia. Alcohol has a complicated relationship with stroke risk, as light consumption may actually decrease the risk of ischemic stroke. However, drinking "even small amounts of alcohol [appears] to increase risk of hemorrhage."
The risk of hypertension, also known as high blood pressure, is influenced by age, bad genetics, salt, potassium, hypertension treatment, and excessive alcohol. In addition to having a high blood pressure, high variability in blood pressure can also be a big risk. Increasing age is a large factor in increasing blood pressure. For people that are "65 and older, more than two-thirds are hypertensive." However, there is less that can be done to mitigate this factor than others. Diet is a very important part of blood pressure. The intake of salt is "associated with an increased risk of hypertension and stroke, whereas increased potassium intake is associated with a decreased stroke risk." Hypertension treatments that can help reduce the risk of stroke exist, but they are unfortunately limited to the treatment quality an individual has access to. Hypertension is thought to be the most important factor of stroke risk; there is a "strong, direct, linear, and continuous relationship between blood pressure and stroke risk." In addition to the observed direct associations between alcohol consumption and stroke risk, excessive alcohol consumption also seems to be increase the risk of hypertension.
Cholesterol is influenced by bad genetics, diet (especially saturated and trans fats), physical activity, and smoking. There is a complex relationship between cholesterol and stroke risk. There are two types of cholesterol: LDL, which is typically regarded as the "bad" kind, and HDL, which is typically regarded as the "good" kind. More HDL cholesterol is associated with a decreased risk of ischemic strokes. More total cholesterol, regardless of the subtypes, is associated with a higher risk of ischemic stroke. However, more total cholesterol seems to decrease the risk of hemorrhagic stroke. A high amount of cholesterol is often referred to as "hyperlipidemia."
Effect of Smoking
The effect smoking has on stroke deaths is significant; approximately 15% of stroke deaths can be attributed to smoking. The effect of smoking for stroke risk seems to be more of a relatively short-term factor, as "smoking cessation rapidly reduces the risk of stroke, with excess risk nearly disappearing 2-4 years after smoking cessation." The effect of smoking on strokes is not limited to the smoking of an individual; second hand smoke is also a significant factor, as exposure to just second hand smoke without individual smoking can still increase the risk of stroke by 30%.
Diabetes is also a significant factor for stroke risk. Diabetics are approximately twice as likely to get strokes than people who aren't diabetic, and they have a 20% chance of their cause of death being a stroke. How long an individual is diabetic also affects their chances of having a stroke. Diabetes is influenced by physical activity, excess calories, and bad genetics.
Waist to Hip Ratio
The amount of fat an individual has influences stroke risk, but the best metric is debated. It seems that the waist to hip ratio, which measures stomach fat, rather than BMI, which measures total weight, has a clearer association with stroke risk. The waist-to-hip ratio is influenced by physical activity and excess calories.
Atrial fibrillation is a type of heart arrhythmia, where "the normal beating in the upper chambers of the heart (the two atria) is irregular, and blood doesn’t flow as well as it should from the atria to the lower chambers of the heart (the two ventricles)" (Atrial Fibrillation). Atrial fibrillation is influenced by atrial cardiopathy, blood pressure, prior history of strokes, bad genetics, and the effect of smoking. It seems that once an individual has a stroke, the risk of atrial fibrillation is increased, thus increasing their chances of a future stroke. Age is one of the factors that leads to increased atrial cardiopathy.
Effect of Infection
The effect that infections have on stroke risk is influenced by the frequency an individual has an infection, vaccine use, and the treatment they receive for their infection. It seems frequent exposure to certain infections can increase the risk of stroke, and an infection can also act as a trigger. Vaccines, such as for influenza, can potentially decrease stroke risk by decreasing the effect of infections. Since people are at a higher risk of a stroke after getting an infection, treating individuals with statins or antiplatelet agents may help reduce risk. Whether an individual is able to get adequate treatment depends on their treatment quality.
The treatment quality one receives is very influential in the chance they have of dying from a stroke. The quality of treatment is influenced by wealth. The more wealth someone has, the more likely they are to see the doctor on a regular basis, work more on their health, and go to the hospital if something is potentially wrong. And more obviously, people who have more money can pay for better care.
Stroke treatment is influenced by treatment quality and faster treatment. The faster the individual gets treatment, the better their chances of surviving. In order to get treatment as soon as possible, it is necessary to be aware of the symptoms of a stroke.
Knowing the symptoms of a stroke and acting accordingly could save a life. If numbness, confusion, trouble seeing, trouble walking, or a severe headache happens suddenly, that could be a sign of a stroke. FAST (face drooping, arm weakness, speech, time to call 9-1-1) is a easy to remember acronym that serves as a simple test for stroke symptoms (Stroke Symptoms).
The Big Picture
Journal Article (unless otherwise specified, the information on this page is based off of this):
Boehme AK, Esenwa C, Elkind MSV. 2017. Stroke Risk Factors, Genetics, and Prevention. Circulation Research [Internet]. [cited 15 Oct 2020];120(3):472-495. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321635/