Stroke mortality dropped rapidly in the US and Canada after folic acid fortification of enriched grain products was fully implemented in 1998, according to a report in the March 14, 2006 issue of Circulation.

The main reason for folic acid fortification was to reduce the occurrence of neural tube defects. The present findings, however, suggest that there may have been an unintended benefit as well.

"There is accumulating, controversial evidence that homocysteine--an amino acid in the blood--is an independent risk factor for stroke and ischemic heart disease," lead author Dr. Quanhe Yang, from the Centers for Disease Control and Prevention in Atlanta, said.  "The increase in folate concentration in the population is inversely associated with homocysteine level," which may help explain the drop in stroke mortality.

Dr. Yang's team compared stroke mortality trends between 1990 and 2002 in the US and Canada with those in England and Wales, where folate fortification is not required.

Stroke mortality was already falling in the US and Canada from 1990 to 1997, but in 1998 a precipitous drop began, the report indicates. In the US, the annual decrease in mortality during the earlier period was 0.3%, whereas starting in 1998 the reduction was 2.9% (p = 0.0005). Similar results were seen in Canada.

Sensitivity analysis suggested that these trends in the US and Canada were probably not due to changes in known stroke risk factors.

By contrast, stroke mortality rates did not decline significantly in England and Wales between 1990 and 2002, the report indicates.

"If folic acid fortification is responsible for even a fraction of the accelerated improvement we observed, this public health benefit is an important bonus to the reduction in neural tube defect rates previously demonstrated," the authors conclude.