Washington, Nov 10 A new study has shown that cumulative exposure to five common infection-causing pathogens is linked to an increased risk of stroke.

Known risk factors for stroke include high blood pressure, heart disease, abnormal cholesterol levels and smoking, but many strokes occur in patients with none of these factors.

Some evidence exists that prior infection with pathogens such as herpes viruses promotes inflammation, contributes to arterial disease and thereby increases stroke risk.

Mitchell S. V. Elkind, M.D., M.S., of Columbia University Medical Center, New York, and colleagues studied 1,625 adults (average age 68.4) living in the multi-ethnic urban community of northern Manhattan, New York.

Blood was obtained from all participants-none of whom had a stroke-and was tested for antibodies indicating prior exposure to five common pathogens: Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus and herpes simplex virus 1 and 2. A weighted composite index of exposure to all five pathogens was developed.

Participants were followed up annually over a median (midpoint) of 7.6 years. During this time period, 67 had strokes.

"Each individual infection was positively, though not significantly, associated with stroke risk after adjusting for other risk factors. The infectious burden index was associated with an increased risk of all strokes after adjusting for demographics and risk factors," the authors said.

The study will appear in the January 2010 print issue of Archives of Neurology, one of the JAMA/Archives journals. (ANI)