Although hypertension (high blood pressure) is a major risk factor for stroke, many people with the disease don't have strokes. Even among people with similar blood pressure levels, stroke risk varies considerably. This led researchers to investigate whether low-grade inflammation could contribute to stroke risk in men with high blood pressure. Inflammation is the process by which the body responds to injury.
The study found that men with systolic blood pressure (the top number in a blood pressure reading) at or above 140 millimeters of mercury (mm Hg) and elevated levels of inflammation-sensitive plasma proteins (ISP) were four times as likely to have a stroke as were men who had normal blood pressure and normal ISP levels. Moreover, the inflammatory proteins predicted stroke risk for 10 or more years.
"It is our conclusion that high ISP levels are associated with elevated blood pressure," says lead author Gunnar Engström, M.D., Ph.D., of Malmo University Hospital in Malmo, Sweden. "These proteins add to the risk of stroke among men with high blood pressure and provide information on stroke risk even after many years of follow-up."
Increased inflammation has been associated with strokes and heart attacks. Inflammation can lead to increases in blood levels of various ISPs, such as fibrinogen, alpha-1 antitrypsin, haptoglobin, ceruloplasmin and orosomucoid. The researchers sought to determine whether these ISPs may contribute to the variability in stroke risk in people with hypertension. They evaluated stroke risk, blood pressure and levels of the five different ISPs in 6,071 healthy Swedish men ages 28 to 61. The men were followed for an average of 18.7 years.
Researchers classified the men according to their systolic blood pressure and according to the number of ISPs in the top quartile - zero to one or two to five. Overall, 238 men had strokes during follow-up.
There was a direct correlation between blood pressure and the number of ISPs in the highest quartile.
Men who had high systolic blood pressure and more than one elevated ISP had a stroke risk 4.3 times higher than that of men with normal blood pressure and fewer elevated ISPs. In contrast, high systolic blood pressure alone increased stroke risk by 2.5 times compared to that of men with normal blood pressure and ISP levels.
An analysis limited to strokes that occurred after more than 10 years of follow-up showed that elevated ISPs still predicted an increased stroke risk. High systolic blood pressure and more than one elevated ISP also predicted an increased risk of death during follow-up. How ISPs affect the risk of stroke and death is not clear, but inflammation may reduce plaque stability or it could accelerate atherosclerosis, the researchers say.
In an accompanying editorial, Keith W. Muir, M.D., of Institute of Neurological Sciences, Glasgow, Scotland, says the research suggests that measuring inflammation may become a valuable additional tool in stroke prevention efforts.
Co-authors of the study are P. Lind, M.D.; B. Hedblad, M.D., Ph.D.; L. Stavenow, M.D. Ph.D.; L. Janzon, M.D., Ph.D. and F. Lindgarde, M.D., Ph.D.
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