Rates of the most common form of stroke begin to increase sharply after age 44, particularly in men, researchers reported in Stroke: Journal of the American Heart Association.

In a Finnish study of 1,008 ischemic stroke patients less than 50 years old, researchers also found:

• a high frequency of stroke risk factors in young patients;
• a high percentage of "silent" and multiple strokes;
• the pattern of stroke-causing events begins changing in midlife to resemble that of the elderly.

"We were surprised by the overall high prevalence of modifiable stroke risk factors in these patients, and particularly in men," said Jukka Putaala, M.D., lead author of the study and a stroke neurologist at Helsinki University Central Hospital. "Furthermore, we did not expect to find so many patients having silent or multiple ischemic strokes."

Younger patients have a different risk-factor profile for ischemic stroke and a wider spectrum of causes compared with elderly patients, Putaala said. For example, cerebral small-vessel disease, large artery atherosclerosis and atrial fibrillation - common underlying causes of ischemic stroke in the elderly - are relatively rare in the young.

Previous stroke studies in younger patients have involved modest numbers, and often did not consider all stroke risk factors. In this study, researchers analyzed trends in demographics for patients who were between ages 15 and 49 and treated for a first ischemic stroke at Helsinki University Central Hospital. Among their findings:

• Although males outnumbered females nearly two to one overall, among stroke patients under age 30, females exceeded males 56 percent to 44 percent.
• The number of strokes increased with age until the incidence rate was almost equal at around age 44. At that point, strokes rapidly increased, particularly in men. For the 45-49 age group, twice as many males as females had strokes.
• The average annual stroke rate for all patients was 13.3 per 100,000 people for males and 7.8 per 100,000 for females. Among patients ages 15-44, the annual rate was 7.5 for males and 5.7 for females.

Traditional stroke risk factors - high cholesterol, smoking, hypertension and obesity - were more common among males and those older than 44. Heavy drinking was more often found in males, and migraine headaches were more common in females as a risk factor. Illicit drug use and migraines were more frequent among younger patients.

・ The leading causes of strokes were caused by a cardiac source (19.6 percent) and artery dissections (15.4 percent).

・ Multiple strokes had occurred in 23 percent of the patients, and silent strokes occurred in 13 percent of the patients.

"Our findings suggest that the risk profile and causes of stroke start to emerge into those seen in older patients in early midlife, and this shift accelerates at around age 44," Putaala said.

The results also demonstrate a need for aggressive strategies to prevent first strokes and recurrence in patients who suffer a stroke, he said. "The most frequent risk factors were all modifiable. Based on our findings, the optimal target age-group for primary prevention of ischemic strokes could be 35 to 44."

The Helsinki University Central Hospital and the University of Helsinki funded the study.

Co-authors are: Antti J. Metso, M.D., Ph.D.; Tiina M. Metso, M.D.; Nina Konkola, M.D.; Yvonn Kraemer, M.D.; Elena Haapaniemi, M.D., Ph.D.; Markku Kaste, M.D., Ph.D.; and Turgut Tatlisumak, M.D., Ph.D.