Elsevier

The Journal of Pediatrics

Volume 153, Issue 5, November 2008, Pages 683-688.e3
The Journal of Pediatrics

Original article
Thymus Size at 6 Months of Age and Subsequent Child Mortality

https://doi.org/10.1016/j.jpeds.2008.04.069Get rights and content

Objective

To examine determinants of thymus size at age 6 months and investigate whether thymus size at this age is a determinant of subsequent mortality.

Study design

Thymus size was measured by transsternal sonography in 923 6-month-old children participating in a measles vaccination trial in Guinea-Bissau.

Results

Thymus size was strongly associated with anthropometric measurements. Boys had larger thymuses than girls, controlling for anthropometry. Crying during sonography made the thymus appear smaller. Children who were not vaccinated with Bacille Calmette-Guérin (BCG) or were vaccinated with BCG in the preceding 4 weeks before inclusion into the study had larger thymuses. Children who had malaria or had been treated with chloroquine or Quinimax in the previous week before inclusion had smaller thymuses. Controlled for background factors associated with thymus size and mortality, small thymus size remained a strong and independent risk factor for mortality (hazard ratio = 0.31; 95% confidence interval = 0.18 to 0.52).

Conclusions

Small thymus size at age 6 months is a strong risk factor for mortality. To prevent unnecessary deaths, it is important to identify preventable factors predisposing to small thymus size.

Section snippets

Study Site

This study was conducted through the Bandim Health Project (BHP) in Bissau, the capital of Guinea-Bissau in western Africa. In 1978, the BHP implemented a demographic surveillance system in the Bissau suburb known as Bandim I, and later expanded it to neighboring areas.8 The study was performed at the Bandim Health Centre, and the subjects resided mainly in Bandim I and Bandim II.

Subjects and Methods

The subjects participated in a randomized 2-dose measles vaccination trial, in which they received either a measles

Study Population

A total of 923 infants (485 boys and 438 girls) were included in the analyses (Figure 1). The median age at study entry was 6.0 months (range, 5.7 to 6.4 months). The median thymic index was 34.3 (range 10.5 to 71.1 months). The median follow-up in the main analysis was 17 months (interquartile range, 13 to 22 months). Of the 923 children, 767 (83%) were scanned on the same day as they were vaccinated, 44 (5%) were scanned before vaccination, and 112 (12%) after vaccination. At age 7.5 months,

Discussion

Our data provide evidence for a large and independent association between thymus size at age 6 months and subsequent mortality. A larger thymus size was associated with significantly reduced mortality controlled for significant background factors. A doubling of thymus size reduced mortality by about 70%.

Among determinants of smaller thymus size, both living in a house with a zinc roof and not having functioning electricity in the house were significant. We have no explanation as to why these 2

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    Funded by the Novo Nordisk Foundation; the Danish Council for Development Research, Science and Technology for Development Programme of the European Community (project IC18-CT95-0011), and the Danish National Research Foundation. The authors have no conflicts of interest to declare.

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