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Parametric modelling of neonatal mortality in relation to size at birth
Author(s) -
Cheung Yin Bun,
Yip Paul S. F.,
Karlberg Johan P. E.
Publication year - 2001
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.858
Subject(s) - hazard ratio , proportional hazards model , covariate , gestational age , term (time) , hazard , demography , neonatology , medicine , statistics , pediatrics , mathematics , pregnancy , confidence interval , physics , biology , ecology , quantum mechanics , sociology , genetics
We use a richly parameterized model to analyse the effects of shortness and thinness at birth on neonatal mortality in Swedish live‐born singletons. The model captures the hazard of neonatal mortality according to the function α ×exp(− γ ×t)+ δ , where t represents age. Covariates are allowed to simultaneously influence the initial excess hazard, the rate of decay, and the long‐term hazard. Among term newborns, birth length for gestational age had a stronger effect on the long‐term hazard and a weaker effect on the initial excess hazard than the Ponderal index. The initial excess hazard associated with a low Ponderal index tended to decay quickly. Among preterm newborns, a higher birth length for gestational age was associated with lower initial and long‐term hazards, and with a faster rate of decay of the initial excess hazard. In contrast, the Ponderal index was not associated with the long‐term hazard. We discuss the interpretability of the model and its potential use in neonatology and medical demography. We also compare the model to a Cox model with time‐dependent covariates. Copyright © 2001 John Wiley & Sons, Ltd.