What Is Stroke?

Arteries are blood vessels that carry oxygen-rich blood from the heart to cells and organs throughout the body. Stroke is a disease that affects the arteries that lead to and pass through the brain. The oxygen and nutrients that brain cells need to function properly are carried around the brain by the blood. When stroke happens, the blood supply to part of the brain is cut off or reduced.

This can be caused by a blockage in an artery (this is called an “ischemic” stroke) or by an artery rupturing, causing bleeding in or around the brain (this is called a “hemorrhagic” stroke). The cells in the affected area of the brain can no longer get all the oxygen and nutrients they need and quickly begin to die. The bleeding can also cause irritation and swelling, and pressure can build up in surrounding tissues, which can increase the amount of damage in the brain.

As well as the two main types of stroke, some people experience “mini-strokes” called transient ischemic attacks (TIAs). A TIA is essentially a stroke caused by a temporary, short-term blockage of an artery. Once the blockage clears the symptoms stop. Although someone who has a TIA may feel better quickly they still need medical attention as soon as possible, because the TIA may be a warning sign that they will have a full stroke in the near future.

What Are the Effects of Stroke?

The effects of stroke differ from one person to another and depend on the severity, the area of the brain that is affected, and the type of stroke experienced. The main symptoms of stroke include one side of the face dropping or the person being unable to smile, not being able to lift both arms and keep them raised, the person having difficulty understanding what you are saying, or slurred speech or not being able to talk.

Other symptoms include confusion or memory loss, numbness or weakness on one side of the body, a sudden fall or dizziness, sudden severe headache, and/or loss of sight or blurred vision (in one or both eyes). Although some people will have a full recovery after stroke, others will have permanent effects that do not get better.

What Causes Stroke?

There are some factors that are known to increase your chance of stroke. These include your age, ethnicity, having a close relative (a sibling, parent, or grandparent) who has had a stroke, especially if the stroke happened before they reached age 65 years, and having other conditions such as diabetes or a type of heart disease. Your arteries naturally become narrower as you get older, and blood clots that cause ischemic stroke often form in areas where arteries have become narrower or blocked over time as a result of the buildup of fatty deposits (a process called “atherosclerosis”).

Smoking, high levels of lipids (fats) in the blood (such as cholesterol and triglycerides), diabetes, drinking excessive amounts of alcohol (binge drinking), obesity, and high blood pressure (also called “hypertension”) can all speed up this process. High blood pressure is also the main cause of hemorrhagic stroke because it can weaken arteries in the brain. The roles of smoking, diabetes, high lipid levels, and high blood pressure in causing stroke are so well known that they are sometimes called “traditional” risk factors.

What Did This Study Investigate?

Although stroke is more common among the elderly it can happen at any age, even in infants. There is some evidence that the global incidence of stroke among younger and middle-aged people (aged 18–64 years) is increasing, with significant increases in low- and middle-income countries. As these countries have undergone economic changes, so too have the dietary and lifestyle habits of their inhabitants, resulting in increases in high blood pressure, diabetes, and obesity.

Although it used to be thought that rare, non-traditional risk factors were mainly responsible for stroke in younger people (such as conditions that mean that a person has a tendency to develop blood clots or rheumatic heart disease), this may no longer be the case.

The authors of this study used data from a study called INTERSTROKE to assess whether traditional risk factors are now the main cause of stroke in people aged 18–45 years. INTERSTROKE was a case–control study that involved 142 centers located in 32 countries across the world between 2007 and 2015. A case–control study is a type of study that compares the medical and lifestyle histories of two different groups of people to identify risk factors that may be associated with a disease or condition:

• one group of people with the disease being studied (cases) and
• another similar group of people who do not have the disease (controls).

In INTERSTROKE, people who experienced their first acute stroke and who presented to medical professionals within 5 days of their symptoms beginning were matched with control participants based on their age and sex. In total, 1,582 pairs of participants were assessed.

What Did the Study Show?

As in older people, ischemic stroke was more common than hemorrhagic stroke in younger adults (accounting for 71% of cases). No statistically significant regional differences in risk factors were identified, although this may have been influenced by the low numbers of participants from individual regions. Traditional risk factors such as high blood pressure, high lipid levels, smoking, excessive alcohol consumption, obesity, and psychosocial stress (caused by our environment and relationships) were also shown to be significant risk factors for stroke in younger adults. High blood pressure was shown to be particularly significant, and was consistently identified as the strongest risk factor across all of the regions included in the study, different stroke types, and both sexes.

These results show that, worldwide, the traditional risk factors for stroke are now as important for younger adults as they are for older members of the population. The authors suggest that public health efforts that aim to identify and address traditional risk factors for stroke should start when people are in their 20s and 30s, which is much earlier than previously thought.

Take-Home Message

Taking steps to control your blood pressure and keep it low, whatever your age, can have significant health benefits that include reducing the risk of stroke. Eating a healthy diet that includes plenty of vegetables, wholegrains, fruit, some dairy products, fish, poultry, nuts, seeds, and beans, and reducing your consumption of sugars and red and processed meat can help. Stopping smoking, only drinking moderate amounts of alcohol (and avoiding binge drinking in particular), and being more active can also have significant positive effects on your health.

Note: This post is based on an article that is not open-access; i.e., only the abstract is freely available.