Parametric modelling of neonatal mortality in relation to size at birth

Stat Med. 2001 Aug 30;20(16):2455-66. doi: 10.1002/sim.858.

Abstract

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 alpha x exp(-gamma x t) + delta, 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Analysis of Variance*
  • Birth Certificates
  • Birth Weight*
  • Body Constitution*
  • Body Height*
  • Body Mass Index*
  • Embryonic and Fetal Development
  • Female
  • Gestational Age
  • Humans
  • Infant Mortality*
  • Infant, Low Birth Weight*
  • Infant, Newborn
  • Likelihood Functions*
  • Male
  • Models, Statistical*
  • Proportional Hazards Models*
  • Registries
  • Risk Factors
  • Sex Characteristics
  • Sex Distribution
  • Survival Analysis
  • Sweden / epidemiology
  • Time Factors