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Population Dynamics Branch (PDB)

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The PDB (formerly the Demographic and Behavioral Sciences Branch) supports research and research training in demography, reproductive health, and population health. In demography, the Branch supports research on the scientific study of human populations, including fertility, mortality and morbidity, migration, population distribution, nuptiality, family demography, population growth and decline, and the causes and consequences of demographic change. In reproductive health, the Branch supports behavioral and social science research on sexually transmitted diseases, HIV/AIDS, family planning, and infertility. In population health, the Branch supports data collection and research on human health, productivity, behavior, and development at the population level, using such methods as inferential statistics, natural experiments, policy experiments, statistical modeling, and gene/environment interaction studies.

New: Research Priorities​

Contraceptive Use and Non-Use

Gap: In the United States, the proportion of pregnancies that are unintended—either mistimed or unwanted—was 45% in 2011, substantially higher than the rate for other industrialized countries1. Most unintended pregnancies in the United States occur because women and their partners either do not use contraception at all, or they use it incorrectly or inconsistently (contraceptive failure accounts for only 5% of unintended pregnancies2).

Priority: Encourage research identifying the factors affecting the non-use or ineffective use of contraception among individuals who are sexually active, but who do not currently desire a pregnancy, and developing effective interventions.

Health and Disease across the Lifespan

Gap: There are several models of how positive and negative exposures affect health and development across the lifespan, but there is limited research on critical periods, identifying which exposures are critical, and the additive and interactive effects of these exposures.

Priority: Support research evaluating whether the effects of early exposures (negative and positive) are cumulative over time, whether these exposures interact with each other, whether there are critical periods (periods during which both negative and positive exposures have substantially greater effects), whether effects of exposures are reversible, and whether exposures early in life increase or decrease sensitivity to future exposures later in life.

Gene–Environment Interactions

Gaps: Rigorous treatment of interactions between genes and the external environment is frequently lacking in the current body of research.​

Priority: Research the effects of environmental exposures on complex phenotypes and how these effects are moderated and mediated by genetic polymorphisms. Environmental exposures include not only the physical environment, but also exposures caused by the social, economic, and policy environments. A focus on non-truncated measures of the environment and an emphasis on the effects of polymorphisms associated with one or more genes, directly or in interaction with each other, are encouraged.


1) In 2011, 45 percent of U.S. pregnancies were unintended (Finder and Zolna 2016), a substantially higher proportion than in Western Europe (34 percent), Oceania (37 percent), Northern Africa (29 percent), and Western Africa (26 percent).  The United States also has a higher adolescent pregnancy rate (41.2% in 2010) than other economically developed countries—Australia 16.5%, Canada 24.0%, Japan 5.0%, and the United Kingdom 29.6% (National Research Council and Institute of Medicine. 2013, pp. 73-74; Dorroch et al. 2001; United Nations Development Programme 2011).

2) Among women at risk for unintended pregnancy, 18 percent use no contraception or stop using contraception for a month or more; they account for 54 percent of all unintended pregnancies. Another 19 percent use contraception incorrectly or inconsistently; they account for 41 percent of unintended pregnancies (Guttmacher Institute 2016).​

Contact Information

Name: Dr Rebecca L Clark
Branch Chief
Population Dynamics Branch
Phone: 301-496-1174
Fax: 301-496-0962

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