Modeling incidence rate ratio and rate difference

Additivity or multiplicativity of human immunodeficiency virus parenteral and sexual transmission among intravenous drug users

M. L C Leite, A. Nicolosi, A. R. Osella, S. Molinari, E. Cozzolino, C. Velati, A. Lazzarin

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The analysis concerns data from the Northern Italian Seronegative Drug Addicts Study, a multicenter longitudinal study about the incidence of human immunodeficiency virus infection in intravenous drug users from Milan and other areas of northern italy between 1987 and 1991. Different measures of parenteral and heterosexual exposure effects were estimated by fitting multiplicative models for rate ratio and additive models for both rate ratio and rate difference into a Poisson regression model for grouped cohort data. In areas of high human immunodeficiency virus prevalence among intravenous drug users, the adjusted rate ratio under a multiplicative structure was 6.2 (95% likelihood-based confidence interval (LCI) 2.9-14.4) for parenteral and 2.9 (95% LCI 1.3-6.1) for sexual transmission. Under the additive model, the rate ratio was 7.8 (95% LCI 3.4-20.2) for parenteral and 9.2 (95% LCI 2.2- 29.7) for sexual transmission, and the rate difference per 100 person-years was 9.8 (95% LCI 5.3-15.6) for parenteral and 10.5 (95% LDI 1.8-24.2) for sexual transmission (controlled for each other). Because of the small sample size, a clear discrimination between models could not be reached. However, in spite of the greater risk associated with parenteral transmission under a multiplicative model, the additive model suggests that the relative impact of measures aimed at inducing condom use is similar to that which would be obtained by measures aimed at stopping syringe sharing.

Original languageEnglish
Pages (from-to)16-24
Number of pages9
JournalAmerican Journal of Epidemiology
Volume141
Issue number1
Publication statusPublished - 1995

Fingerprint

Drug Users
HIV
Confidence Intervals
Incidence
Needle Sharing
Heterosexuality
Condoms
Virus Diseases
Sample Size
Italy
Multicenter Studies
Longitudinal Studies

ASJC Scopus subject areas

  • Epidemiology
  • Geriatrics and Gerontology

Cite this

Modeling incidence rate ratio and rate difference : Additivity or multiplicativity of human immunodeficiency virus parenteral and sexual transmission among intravenous drug users. / Leite, M. L C; Nicolosi, A.; Osella, A. R.; Molinari, S.; Cozzolino, E.; Velati, C.; Lazzarin, A.

In: American Journal of Epidemiology, Vol. 141, No. 1, 1995, p. 16-24.

Research output: Contribution to journalArticle

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