Neural tube defects decrease with folic acid fortification

A new study published online April 21, 2005 in the American Journal of Medical Genetics Part A examines whether the recent decline in neural tube defects in Chile was due to the addition of folic acid to wheat flour in that country or to pre-existing decreasing trends. The journal is available online via Wiley InterScience.

Recent data in Chile have suggested that the incidence of the neural tube defects spina bifida and anencephaly (a fatal condition that results in malformation of the brain) have significantly declined since January 2000, when wheat flour began to be fortified with folic acid. In that time, Chile has been fortifying its foods at double the rate of the U.S. In order to determine if the decrease was directly attributable to the addition of folic acid as opposed to an independent trend, the study examined historical data from before the fortification and compared it to data from a two-year period after fortification began.

Led by Eduardo E. Castilla, of the genetics department at the Instituto Oswaldo Cruz in Rio de Janeiro, Brazil, researchers performed a survey of maternity hospitals in the ECLAMC (Latin American Collaborative Study of Congenital Malformations) network in Chile between the years 1982 and 2002. The data were divided between the pre-fortification years 1982-1989 and 1990-2000 to provide a baseline, and 2001-2002, the period during which flour was fortified. While the prevalence rates of neural tube defects did not significantly change between the two pre-fortified periods, the rate of spina bifida decreased by 51 percent and the rate of anencephaly decreased by 46 percent in the 2001-2002 period. Because different hospitals might experience different rates in neural tube defects at different times, the study examined only those hospitals with data for two consecutive periods.

According to the authors, one of the main strengths of the study is that because abortion is illegal in Chile, the data contain virtually all cases of neural tube defects. Furthermore, the study confirms preliminary results following folic acid fortification that were observed 20 months after fortification began. In addition, the inclusion of two pre-fortification periods successfully demonstrated that the decrease in neural tube defects seen in 2001-2002 was not due to a historical trend like in other areas of the world, including the U.S., where decreasing trends are documented.

Based on their comparison of two pre-fortification periods, the authors conclude: "In summary, we demonstrated that neural tube defect prevalence rates were not decreasing in Chile before the start of folic acid fortification in the year 2000." They note that the results of this study are similar to studies conducted from other folic acid fortified populations in Canada and the U.S. and state that more precise estimates will be provided by ECLAMC during the next few years.