Strategies for assessing the impact of loss to follow-up on estimates of neurodevelopmental impairment in a very preterm cohort at 2 years of age
Aurélie Piedvache, Stef van Buuren, Henrique Barros, Ana Isabel Ribeiro, Elizabeth S. Draper, Jennifer Zeitlin, E. J. Martens, Geert A. Martens, Patrick Van Reempts, Klaus Boerch, Asbjørn Børch Hasselager, Lene Drasbek Huusom, Ole Pryds, Tom Weber, Liis Toome, Heili Varendi, Ile-de France, Pierre‐Yves Ancel, Béatrice Blondel, A. Burguet, P.-H. Jarreau, Patrick Truffert, Rolf F. Maier, Björn Misselwitz, Stephan Schmidt, Ludwig Gortner, Dante Baronciani, G Gargano, Rocco Agostino, D DiLallo, Francesco Franco, Virgilio Carnielli, C. Koopman-Esseboom, Arno van Heijst, Joppe Nijman, Janusz Gadzinowski, Jan Mazela, Luís M. Graça, Marcel Cerqueira César Machado, Carina Rodrigues, Teresa Rodrigues, A. K. Edstedt Bonamy, Mikael Norman, E. Wilson E Boyle, Elizabeth S. Draper, Bradley N Manktelow, Alan Fenton, David Milligan, Jennifer Zeitlin, Mercedes Bonet, A. Piedvache
Abstract
BACKGROUND: Loss to follow-up is a major challenge for very preterm (VPT) cohorts; attrition is associated with social disadvantage and parents with impaired children may participate less in research. We investigated the impact of loss to follow-up on the estimated prevalence of neurodevelopmental impairment in a VPT cohort using different methodological approaches. METHODS: This study includes births < 32 weeks of gestational age (GA) from 4 regions in the UK and Portugal participating in a European birth cohort (N = 1737 survivors). Data on maternal characteristics, pregnancy complications, neonatal outcomes and neighborhood deprivation were collected at baseline. Neurodevelopment was assessed at 2 years of corrected age (CA) using standardized parent-report measures. We applied (1) multiple imputation (MI) and (2) inverse probability weighting (IPW) to estimate the impact of non-response on the prevalence of moderate to severe neurodevelopmental impairment and assessed violations of the missing at random (MAR) assumption using the delta method. RESULTS: 54.2% of children were followed-up. Follow-up was less likely when mothers were younger, multiparous, foreign-born, did not breastfeed and came from deprived areas. The prevalence of neurodevelopmental impairment was 18.4% (95% confidence interval (CI):15.9-21.1) and increased to 20.4% (95%CI: 17.3-23.4) and 20.0% (95%CI:16.9-23.1) for MI and IPW models, respectively. Simulating strong violations of MAR (children with impairments being 50% less likely to be followed-up) raised estimates to 23.6 (95%CI:20.1-27.1) CONCLUSIONS: In a VPT cohort with high loss to follow-up, correcting for attrition yielded modest increased estimates of neurodevelopmental impairment at 2 years CA; estimates were relatively robust to violations of the MAR assumption.