Testing the epidemiological paradox through birthweight in the Spanish context: a true or an artificial effect?

Sol Juárez, Spanish Council for Scientific Research
George B. Ploubidis, London School of Hygiene and Tropical Medicine (LSHTM)
Lynda Clarke, London School of Hygiene and Tropical Medicine (LSHTM)

This study examines the implications of applying the common threshold definition of low birth weight (below 2,500 grams) in order to detect the presence of the ‘low birth weight paradox’, while, at the same time, testing whether it is present in Spain as reported for other countries with longer migration histories, such as the United States of America. A wide range of studies have offered explanations for this paradox but none of them has produced conclusive results. More importantly, previous studies focus on investigating the mechanisms underlying the paradox without contemplating the possible existence of an artificial effect due to methodological bias. The main aim of this paper is to explore such a possibility in producing bias in the findings by presenting different measurement approaches and definitions of the epidemiological paradox with respect to perinatal health.