A study published in the American Journal of Public Health published May 15, 2014 confirms that water fluoridation does not have the effect of lowering IQ's. The study was published by the New Zealand University of Otago. It followed 1,000 people born in Denedin, New Zealand in 1972 and 1973 and studied all aspects of their health and development up to their thirty-eighth birthdays. Lead author, Dr. Jonathan Broadbent says the research focused especially on the first five years of the study members lives, which is a critical period in brain development. He also looked at their development between the ages of 7-13 and again at age 38. Researches considered other factors such as socio-economic status of parent, birth weight and breastfeeding, as well as secondary and tertiary scholastic achievement, all of which can have an effect on IQ. The analysis showed no significant differences in IQ by fluoride exposure, even before considering the other factors that might influence scores. Breastfeeding is associated with higher scores, as reported in the this and other studies, however.