Almost everyone who has a stroke had at least one common heart risk factor like high blood pressure, cholesterol, blood sugar, or a history of smoking—so strokes hardly ever happen to people with perfectly healthy heart numbers.

What we've found so far is that nearly all people who have a stroke had at least one common heart-related risk factor beforehand, such as high blood pressure, high cholesterol, high blood sugar, or a history of smoking [1]. Our analysis of the available evidence shows that strokes rarely occur in people without any of these risk factors [1]. The evidence we've reviewed leans toward the idea that having one or more of these health issues is very common among people who experience a stroke. In fact, based on what we’ve seen so far, almost every stroke case was preceded by at least one of these well-known risk markers [1]. This suggests that these factors may play a major role in stroke risk, though we can’t say from this evidence alone how strong that role is or whether other factors might also be involved. We only analyzed one assertion so far, supported by data from 49.0 studies, with no studies refuting it [1]. While this number of supporting studies suggests a strong pattern, we are still building our understanding. Our current analysis does not rule out the possibility that some people have strokes without these risk factors—we just don’t have evidence of that in what we’ve reviewed so far. Because our findings are based on limited assertions, we need to be clear: this is not a final picture. As we analyze more research over time, our understanding may change. Practical takeaway: Most people who’ve had a stroke had high blood pressure, cholesterol, blood sugar, or a smoking history first—so keeping an eye on these health numbers might be one of the most important things you can do for your long-term well-being.