Long-term follow-up of randomised trials and observational studies provide the best evidence presently available to assess long-term effects of nutrition, and such studies are an important component in determining optimal infant feeding practices. Attrition is, however, an almost inevitable occurrence with increasing age at follow-up. There is a common assumption that studies with <80% follow-up rates are invalid or flawed, and this criticism seems to be more frequently applied to follow-up studies involving randomised trials than observational studies. In this article, we explore the basis and evidence for this "80% rule" and discuss the need for greater consensus and clear guidelines for analysing and reporting results in this specific situation.

attrition, loss to follow-up, nutrition, observational studies, paediatrics, randomised trials
dx.doi.org/10.1097/MPG.0000000000000992, hdl.handle.net/1765/90484
Journal of Pediatric Gastroenterology and Nutrition
Erasmus MC: University Medical Center Rotterdam

Fewtrell, M, Domellöf, M, Hojsak, I, Hulst, J.M, Kennedy, K, Koletzko, B, … Stijnen, Th. (2016). Attrition in long-term nutrition research studies: A commentary by the european society for pediatric gastroenterology, hepatology, and nutrition early nutrition research working group. Journal of Pediatric Gastroenterology and Nutrition, 62(1), 180–182. doi:10.1097/MPG.0000000000000992