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Estimating duration in partnership studies: issues, methods and examples
  1. Bart Burington1,
  2. James P Hughes2,
  3. William L H Whittington3,
  4. Brad Stoner4,
  5. Geoff Garnett5,
  6. Sevgi O Aral6,
  7. King K Holmes3
  1. 1Genentech, San Francisco, California, USA
  2. 2Department of Biostatistics, University of Washington, Seattle, Washington, USA
  3. 3Department of Medicine, University of Washington, Seattle, Washington, USA
  4. 4Department of Anthropology, Washington University, St Louis, Missouri, USA
  5. 5Department of Infectious Disease Epidemiology, Imperial College, London, UK
  6. 6Centers for Disease Control and Prevention, Atlanta, Georgia, USA
  1. Correspondence to Dr James P Hughes, Department of Biostatistics, University of Washington 357232, Seattle, WA 98115, USA; jphughes{at}


Background and objectives Understanding the time course of sexual partnerships is important for understanding sexual behaviour, transmission risks for sexually transmitted infections (STI) and development of mathematical models of disease transmission.

Study design The authors describe issues and biases relating to censoring, truncation and sampling that arise when estimating partnership duration. Recommendations for study design and analysis methods are presented and illustrated using data from a sexual-behaviour survey that enrolled individuals from an adolescent-health clinic and two STD clinics. Survey participants were queried, for each of (up to) four partnerships in the last 3 months, about the month and year of first sex, the number of days since last sex and whether partnerships were limited to single encounters. Participants were followed every 4 months for up to 1 year.

Results After adjustment for censoring and truncation, the estimated median duration of sexual partnerships declined from 9 months (unadjusted) to 1.6 months (adjusted). Similarly, adjustment for censoring and truncation reduced the bias in relative risks for the effect of age in a Cox model. Other approaches, such as weighted estimation, also reduced bias in the estimated duration distribution.

Conclusion Methods are available for estimating partnership duration from censored and truncated samples. Ignoring censoring, truncation and other sampling issues results in biased estimates.

  • Biostatistics
  • mathematical model
  • sexual networks
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  • Funding The work was supported by National Institutes of Health grants AI31448 and AI29168.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the University of Washington.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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