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Because ‘traditional’ tracking analyses have some drawbacks, this paper presents a new method, which is based on generalized estimating equations (GEE). The new method is illustrated with data from the Amsterdam Growth and Health Study. In this observational longitudinal study six repeated measurements were carried out on 181 subjects (initial age 13 years) over a period of 15 years. Tracking was assessed for total cholesterol (TC), high density lipoprotein (HDL) and the TC/HDL ratio by calculating the odds ratio (OR) for subjects at risk at the age of 13 years regarding the development of their risk status over a 15 year period. These ORs can be interpreted as tracking coefficients. Three methods were compared: percentage of subjects who maintain their position in a certain risk group (i.e. univariate logistic regression), multivariate logistic regression and GEE. The three methods differ in the possibility of using all available data in the analysis and in the possibility of adjusting for certain covariates. Based on this, the GEE-approach seemed to be the most appropriate to calculate tracking coefficients for subjects at risk. When the risk groups were defined according to objective (absolute) risk values, for TC the GEE-OR was 10.1 (95% confidence interval (CI) 5.0–21.9), for HDL 14.4 (95% CI 7.2–28.7) and for the TC/HDL ratio 25.5 (95% CI 11.5–56.8). It can be concluded that the GEE-approach is very suitable to assess tracking for subjects at risk.

This study aimed to assess whether previously established risk factors for sudden infant death syndrome (SIDS) are still valid now that the incidence in the Netherlands has dropped to 0.26 per 1000 liveborn infants. A distinction was made between immutable and mutable risk factors. This case-control study (part of the European Concerted Action on SIDS) comprised 73 SIDS cases and 146 controls and lasted from March 1995 to September 1996. Adjustments were made for sleeping position and bedding factors by treating them as covariables. Apart from these factors, well known risk factors that remain of importance in the Netherlands are: male sex, young maternal age, twins, and low socioeconomic status. These factors are largely immutable. Other well known risk factors which might reflect attitudes to child care and could possibly be mutable are: smoking, alcohol consumption by the mother, bottle feeding, and change of babycare routine. Intervention strategies should focus on early signalling, thereby assisting parents in changing these unfavourable parenting attitudes. Information on optimal child care and extra support by public health nurses specifically aimed at families at risk could help to decrease further the incidence of SIDS in the Netherlands.