The odds of having a stroke are twice as high for people whose father or mother had a stroke by age 65, yet more research confirms.
The study authors say their findings are so clear, they believe parental stroke history should be included as a significant risk factor when assessing a patient's stroke risk.
For the study, in the online edition of Circulation, researchers from Boston University School of Medicine collected data on 3,443 people who participated in the Framingham Heart Study.
The ongoing study on the health of residents of the town of Framingham, Massachusetts, began in 1948 and is now on its third generation of participants. The study provides researchers with complete data on medical history as well as lifestyle data, such as diet.
Among the parents of the participants, 106 had strokes by the time they were 65. Among the current participants, 128 had strokes over the 40 years of the study.
After taking into account the usual risk factors for stroke, the researchers found that people who had a parent who had a stroke by the time they were 65 had twice the risk of having a stroke at any age.
What's more, children of those affected by stroke by age 65 had four times the risk of having a stroke by the time they themselves reached 65.
"The study shows that parental stroke by age 65 is a powerful risk factor for stroke in the offspring," Dr. Sudha Seshadri, an associate professor of neurology at Boston U. said in a news release.
Seshadri says her team helped rule out the possibility that the link was due to shared risk factors, by adjusting for such things as high blood pressure, diabetes, smoking status, and age. They found the link held both in offspring who had other risk factors and those who didn't, although the effect was greatest among offspring who had other risk factors.
For reasons not understood, the data also suggested the impact of a father's stroke on offspring was weaker than a mother's.
Since most of the Framingham study participants were of European ancestry, the findings need to be tested in minority population, Seshadri said. But she added she believed that parental stroke might be as important a risk factor for stroke as high blood pressure.
She notes that since the biggest effect of a parental stroke is on offspring who have strong stroke risk factors, a family history of stroke should motivate people to take better control of their blood pressure, to quit smoking, exercise and maintain an ideal weight.
