Obtaining vital status and cause of death on a million persons

Abstract

Purpose

To present the methodology used to determine vital status and obtain cause of death (COD) within the Million Person Study of Low-Dose Health Effects (MPS). Data sources and vital status tracing techniques used to obtain vital status and COD for six (n = 424,238 subjects) of the ∼20+ cohorts under study are described.

Methods and materials

A multistage approach using multiple sources of vital status information was used to determine vital status (or ‘trace’) study participants from as early as 1940 to the present. Mortality records from state departments of vital statistics and the Social Security Administration Death Master File (SSA-DMF) were matched to study participants by Social Security Number (SSN), full name, date of birth (DOB), and/or sex using deterministic and probabilistic algorithms. The National Death Index (NDI) and SSA Service for Epidemiological Researchers (SSA-SER) were used to obtain COD (after 1978) and verification of alive status, respectively. Online public records and ancestry services, death certificates, and specialized mortality sources were also utilized.

Results

For the MPS cohorts traced to date (nuclear power plant workers, industrial radiographers, atomic veterans, and workers at Rocketdyne/Atomics International, Mound nuclear facility, and Mallinckrodt Chemical Works), vital status was confirmed for over 90% of all study subjects in all but one cohort (88%). The ascertainment of COD was over 96% for all cohorts.

Conclusions

A hallmark of a high-quality epidemiologic cohort mortality study is a low percentage of subjects with unknown vital status and a low percentage of deaths without a COD. The sources and methods used for vital status tracing and COD determination for the MPS have been successful and should be useful for other investigators tracing large, historic study populations. Some of the approaches would be applicable for use in all cohort studies using regional-specific mortality data or modifications to the approach.

Keywords:

• Vital status
• cause of death
• cohort study
• social security
• National Death Index

Disclosure statement

The authors report no conflict of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This work was supported in part by a grant from the U.S. Nuclear Regulatory Commission [NRC-HQ‐60‐14‐G‐0011], a grant from the Centers for Disease Control and Prevention [5UE1EH000989] a grant from the National Aeronautics and Space Administration [Grant No. NNX15AU88G], and grants from the U.S. Department of Energy [Grant No. DE-SC0008944 and Grant No. DE-AU0000042 awarded to the National Council on Radiation Protection and Measurements, which included interagency support from the U.S. Nuclear Regulatory Commission, the U.S. Environmental Protection Agency, and the National Aeronautics and Space Administration). Further, contract support was received by Oak Ridge National Laboratory from the Office of Radiation and Indoor Air, U.S. Environmental Protection Agency, under Interagency Agreement DOE No. 1824 S581‐A1, under contract No. DE-AC05‐00OR22725 with UT-Battelle; and contract support was received by Oak Ridge Associated Universities from the U.S. Department of Energy under contract No. DE-SC0014664.

Notes on contributors

Michael T. Mumma

Michael Mumma is the Director of Information Technology at the International Epidemiology Institute and the International Epidemiology Field Station for Vanderbilt University Medical Center. He has over 20 years of experience in data analysis and conducting epidemiologic investigations.

Sarah S. Cohen

Sarah Cohen is a Principal Epidemiologist at EpidStat Institute where she directs observational research studies in the areas of pharmacoepidemiology, nutritional epidemiology, and occupational epidemiology as well as leads large data management projects and statistical analyses. She is also an Adjunct Assistant Research Professor of Medicine in the Department of Medicine at Vanderbilt University School of Medicine. She has been a collaborator on the MPS for nearly 20 years, providing analytic support as well as co-authoring numerous publications.

Jennifer L. Sirko

Jennifer L. Sirko is an epidemiologist with over 10 years of experience in occupational and public health research. In addition to her work with the International Epidemiology Institute, she is currently a research officer with the Pew Charitable Trusts.

Elizabeth D. Ellis

Elizabeth (Betsy) Dupree Ellis currently works in the Health, Energy and the Environment Program, Oak Ridge Associated Universities. Dr. Ellis does research in Public Health, Occupational Health, and Epidemiology. A major project is contributing to the ‘Million Person Study’. She is also active in human subject protection in research.

John D. Boice

John Boice is President of the National Council on Radiation Protection and Measurements and Professor of Medicine at Vanderbilt University. He is an international authority on radiation effects and served on the Main Commission of the International Commission on Radiological Protection and on the United Nations Scientific Committee on the Effects of Atomic Radiation. He directs the Million Person Study of Low-Dose Health Effects.