High blood pressure is the single biggest factor that increases stroke risk, but it’s far from the only one. Stroke risk comes from a combination of conditions, habits, and traits, some you can change and some you can’t. Understanding which factors apply to you is the first step toward lowering your overall risk.
High Blood Pressure
Blood pressure is the most important modifiable risk factor for stroke. When blood pushes too hard against artery walls over time, it damages the vessels that supply your brain, making them more likely to narrow, stiffen, or rupture. The threshold for high blood pressure is a systolic (top number) reading of 130 or higher, or a diastolic (bottom number) reading of 80 or higher.
The numbers tell a clear story. People with only elevated systolic pressure (130 to 139) have a 36% increased risk of stroke compared to those with normal readings. High diastolic pressure alone (80 to 89) raises risk by 32%. When both numbers are elevated, the risk climbs 67%. These findings, from research published by the American Heart Association, underscore that both numbers matter, not just the top one.
What makes high blood pressure so dangerous is that most people don’t feel it. You can walk around for years with readings in the 140s or 150s and have no symptoms at all, while the damage to your blood vessels quietly accumulates.
Atrial Fibrillation
Atrial fibrillation, often called AFib, is an irregular heartbeat that causes the upper chambers of the heart to quiver instead of contracting normally. When blood doesn’t move through the heart efficiently, it can pool and form clots. If one of those clots travels to the brain, it blocks blood flow and causes a stroke.
The risk is substantial: people with AFib are five times more likely to have a stroke than people with a normal heart rhythm. AFib-related strokes also tend to be more severe, because the clots that form in the heart are often larger than those caused by narrowed arteries. Many people with AFib don’t know they have it, since episodes can come and go without obvious symptoms. A racing or fluttering feeling in the chest, unexplained fatigue, or dizziness can all be signs worth investigating.
Diabetes
Type 2 diabetes raises your risk of ischemic stroke (the kind caused by a blocked blood vessel) by 37%. High blood sugar damages blood vessels over time in much the same way high blood pressure does, promoting the buildup of fatty deposits inside artery walls. People with diabetes are also more likely to have other stroke risk factors stacked on top, including high blood pressure, high cholesterol, and obesity.
Interestingly, diabetes does not appear to increase the risk of hemorrhagic stroke, the less common type caused by a burst blood vessel. The danger is specifically tied to blockages. Keeping blood sugar well managed reduces that vascular damage and lowers your overall risk profile.
High Cholesterol
Excess LDL cholesterol, the type often called “bad” cholesterol, contributes to stroke by building up inside the walls of arteries that supply the brain. This process, called atherosclerosis, narrows those arteries and makes them prone to forming clots. The carotid arteries in the neck are especially vulnerable, and a blockage there is one of the most common pathways to stroke.
LDL cholesterol can also cause problems in smaller vessels deep inside the brain, where tiny fatty deposits can rupture and trigger clots in areas that are difficult to treat. The connection between cholesterol and stroke is strongest for strokes caused by large artery blockages, which tend to cause the most widespread brain damage.
Smoking
Smoking roughly doubles your risk of stroke. Chemicals in cigarette smoke thicken the blood, raise blood pressure, and accelerate the buildup of plaque inside artery walls. It also reduces the amount of oxygen your blood can carry, which means your brain is already working at a disadvantage before anything goes wrong.
The good news is that the damage reverses faster than most people expect. Within two to twelve weeks of quitting, circulation begins to improve. After two years, stroke risk drops significantly. After five years, a former smoker’s risk returns to the same level as someone who never smoked. Few lifestyle changes offer that kind of measurable payoff on a defined timeline.
Diet and Sodium
A diet high in sodium raises blood pressure, which in turn raises stroke risk. The World Health Organization recommends adults consume less than 2,000 milligrams of sodium per day, roughly equivalent to just under a teaspoon of salt. Most people in Western countries consume well above that threshold, often without realizing it, because sodium is concentrated in processed and restaurant foods rather than what you add at the table.
Beyond sodium, diets low in fruits, vegetables, and whole grains are independently associated with higher stroke risk. These foods provide potassium, which helps counterbalance sodium’s effect on blood pressure, along with fiber and antioxidants that support vascular health. You don’t need a radical overhaul. Even modest shifts, like replacing processed snacks with whole foods and cooking more meals at home, meaningfully reduce sodium intake over time.
Sleep Apnea
Obstructive sleep apnea, a condition where the airway repeatedly collapses during sleep, is an underrecognized stroke risk factor. Each time breathing stops, oxygen levels in the blood drop and the nervous system fires off an emergency response. This triggers blood pressure surges that can reach as high as 220/130 and disruptions to heart rhythm, including pauses where the heart temporarily stops beating.
These episodes repeat dozens or even hundreds of times per night. Over months and years, the repeated oxygen deprivation and blood pressure spikes cause chronic damage to blood vessels and promote the kind of inflammation that accelerates plaque buildup. People with untreated sleep apnea are also more likely to develop high blood pressure, AFib, and other conditions that independently raise stroke risk, creating a compounding effect. Loud snoring, gasping during sleep, and persistent daytime fatigue are common signs.
Hormonal Factors in Women
Women face several stroke risk factors that don’t apply to men. Combination birth control pills containing estrogen roughly double the risk of ischemic stroke. Modern low-dose formulations carry a lower risk than older high-dose pills, but the increase is still meaningful. For nonsmoking women with normal blood pressure, the absolute numbers remain small: about 8.5 strokes per 100,000 users per year, compared to 4.4 per 100,000 in nonusers. Smoking or having high blood pressure while on combination pills raises the risk further. Progestin-only pills do not appear to increase stroke risk at all.
Pregnancy also raises stroke risk. The rate climbs from about 21 strokes per 100,000 women to 34 per 100,000 deliveries. Pregnancy-related conditions like preeclampsia, which involves dangerously high blood pressure, account for much of this increase. Women who develop preeclampsia carry elevated cardiovascular risk for years afterward, making it a red flag worth monitoring long after delivery.
Air Pollution
Living in areas with high levels of fine particulate matter (the tiny particles produced by traffic, industry, and wildfires) is an emerging stroke risk factor. Both short-term spikes and long-term exposure to polluted air are associated with increased rates of ischemic stroke. The particles are small enough to pass from the lungs into the bloodstream, where they trigger inflammation and promote clotting.
Research published in The Lancet Planetary Health found that even a modest increase in particulate matter concentration in the days before a stroke event was associated with a 5 to 10% increase in risk. For people already carrying other risk factors, that incremental push can be enough to tip the balance. Checking air quality indexes on high-pollution days and reducing outdoor exertion during poor air quality are practical steps, particularly for people in urban environments.
Age, Race, and Family History
Some stroke risk factors are outside your control. Stroke risk increases with age, roughly doubling every decade after 55. A family history of stroke, particularly in a parent or sibling who had one before age 65, raises your risk as well, likely through a combination of shared genetics and shared lifestyle patterns.
Race plays a significant and well-documented role. Black Americans have stroke death rates two to five times higher than all other racial and ethnic groups in every region of the United States, according to data from the National Center for Health Statistics. Black men in the South face the highest rates, at 65.7 deaths per 100,000, while Black women face rates that are at least double those of other groups across all regions. These disparities reflect a combination of higher rates of hypertension, less access to preventive care, and systemic health inequities that compound over a lifetime.
How Risk Factors Stack
Stroke risk isn’t determined by any single factor in isolation. It’s the combination that matters. Someone with mildly elevated blood pressure, borderline cholesterol, and untreated sleep apnea faces a very different risk profile than someone with just one of those conditions. Each additional factor doesn’t simply add to the risk; the effects multiply. This is why addressing even one or two modifiable factors, quitting smoking, getting blood pressure under control, or treating sleep apnea, can produce an outsized reduction in overall stroke risk, even when other factors remain.