PubMed · 9762516
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J M Samet, A Muñoz. 1998. Perspective: cohort studies.. https://doi.org/10.1093/oxfordjournals.epirev.a017968
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OBJECTIVE: To assess neonatal intensive care unit (NICU) practices affecting screening and follow-up for retinopathy of prematurity (ROP). METHODS: Retrospective study of infants at risk for ROP, eligible for back transport, admitted to a regional NICU from January 1, 1999 until May 31, 2002. Patients failed to receive needed follow-up for ROP after discharge or transfer from a NICU, if we could not verify their ROP screening follow-up within 1 month. RESULTS: A total of 74 infants were identified to need follow-up eye care. Infants who did not receive the follow-up care had greater mean gestational age (mean SD; 30.7+/-2.3 vs 29.6+/-2.5 weeks, p=0.05) and birth weights (mean SD; 1581+/-366 vs 1360+/-508 g, p=0.007), compared to infants who received the recommended care. Infants transported back to the community hospital were significantly more likely to miss follow-up eye care compared to infants discharged from the regional center (relative risk 2.81, 95% confidence interval (CI) (1.09 to 7.20)). Infants not screened for ROP in the NICU had greater risk for missing follow-up care compared to infants who had their first retinal examination in the NICU (relative risk 4.25, 95% CI (1.42 to 12.73)). CONCLUSIONS: Infants transferred back or discharged from the NICU before ROP screening represent a high-risk group for not receiving follow-up eye care.
Nicotine and its metabolite cotinine are important biochemical markers to determine active or passive exposure to cigarette smoke. The amount of nicotine and cotinine in hair provides a cumulative index of tobacco exposure. This study uses segmental hair analysis to assess changes in nicotine metabolism in a cohort of pregnant women who smoked steadily during the whole gestational period according to their self-report. Maternal hair was collected at the time of delivery and sectioned into segments representing the three trimesters of pregnancy. The concentrations of nicotine and cotinine in each section of hair were measured by radioimmunoassay. Hair concentration of nicotine decreased during pregnancy without any reported reduction in smoking, while the cotinine concentration remained constant. The nicotine-cotinine ratio in these consistent smokers was: 1st trimester 20.6, 2nd trimester 19.9, and 3rd trimester 13.3. These findings are consistent with results from other studies showing increased nicotine metabolism during pregnancy. Our data suggest that the results of segmental hair analysis should be carefully examined in pregnancy. Both nicotine and cotinine levels should be evaluated in order to confirm any significant change in maternal tobacco exposure during pregnancy.
We present a regression modelling framework to analyse infectious disease transmission during a time period where extensive exposure data are available, but where the outcome data are sparse. A latent variable model is used for each exposure time, allowing a straight-forward accumulation of risk for a collection of exposures for which outcome data are available. We describe an analysis of HIV infection from blood products among a cohort of haemophiliacs in Ireland between 1980 and 1985. The analysis provides estimates of the time pattern and batch effects; we show how analytical complexity such as smoothly varying coefficients or random coefficient models can be accommodated by the model. Finally, we discuss other problems where the model is applicable.