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Mortality in British military participants in human experimental research into chemical warfare agents at Porton Down: cohort study

BMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b613 (Published 25 March 2009) Cite this as: BMJ 2009;338:b613
  1. K M Venables, reader in occupational medicine1,
  2. C Brooks, data manager 1,
  3. L Linsell, medical statistician1,
  4. T J Keegan, research fellow1,
  5. T Langdon, assistant data manager1,
  6. T Fletcher, senior lecturer in environmental epidemiology2,
  7. M J Nieuwenhuijsen, research professor in environmental epidemiology3, visiting professor4,
  8. N E S Maconochie, senior lecturer in epidemiology and medical statistics5,
  9. P Doyle, professor of epidemiology5,
  10. V Beral, professor and director 6,
  11. L M Carpenter, reader in statistical epidemiology1
  1. 1Department of Public Health, University of Oxford, Oxford OX3 7LF
  2. 2Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, London
  3. 3Centre for Research in Environmental Epidemiology, IMIM and CIBERESP, 08003 Barcelona, Spain
  4. 4Division of Epidemiology, Public Health and Primary Care, Imperial College, London
  5. 5Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London
  6. 6Cancer Epidemiology Unit, University of Oxford, Oxford
  1. Correspondence to: K M Venables kate.venables{at}dphpc.ox.ac.uk; L M Carpenter lucy.carpenter{at}dphpc.ox.ac.uk
  • Accepted 5 December 2008

Abstract

Objective To investigate any long term effects on mortality in participants in experimental research related to chemical warfare agents from 1941 to 1989.

Design Historical cohort study.

Data sources Archive of UK government research facility at Porton Down, UK military personnel records, and national death and cancer records.

Participants 18 276 male members of the UK armed forces who had spent one or more short periods (median 4 days between first and last test) at Porton Down and a comparison group of 17 600 non-Porton Down veterans followed to 31 December 2004.

Main outcome measures Mortality rate ratio of Porton Down compared with non-Porton Down veterans and standardised mortality ratio of each veteran group compared with the general population. Both ratios adjusted for age group and calendar period.

Results Porton Down veterans were similar to non-Porton Down veterans in year of enlistment (median 1951) but had longer military service (median 6.2 v 5.0 years). After a median follow-up of 43 years, 40% (7306) of Porton Down and 39% (6900) of non-Porton Down veterans had died. All cause mortality was slightly greater in Porton Down veterans (rate ratio 1.06, 95% confidence interval 1.03 to 1.10, P<0.001), more so for deaths outside the UK (1.26, 1.09 to 1.46). Of 12 cause specific groups examined, rate ratios in Porton Down veterans were increased for deaths attributed to infectious and parasitic (1.57, 1.07 to 2.29), genitourinary (1.46, 1.04 to 2.04), circulatory (1.07, 1.01 to 1.12), and external (non-medical) (1.17, 1.00 to 1.37) causes and decreased for deaths attributed to in situ, benign, and unspecified neoplasms (0.60, 0.37 to 0.99). There was no clear relation between type of chemical exposure and cause specific mortality. The mortality in both groups of veterans was lower than that in the general population (standardised mortality ratio 0.88, 0.85 to 0.90; 0.82, 0.80 to 0.84).

Conclusions Mortality was slightly higher in Porton Down than non-Porton Down veterans. With lack of information on other important factors, such as smoking or service overseas, it is not possible to attribute the small excess mortality to chemical exposures at Porton Down.

Footnotes

  • We thank the research team who worked on the study (Monica Smith, Marita Lowry, Alison Howell, Margaret Chandler, Owen Rogers, the late Janice Hurwood, Sue Walker, Chris Shield, Nicola Pata, Kate Brockhurst, Steve Davies, Ian Palmer, and Madeleine Harwood); staff from the Ministry of Defence (MoD) who abstracted personnel data for the study; and Bianca De Stavola, David Cox, and Michael Hills for input on analytical methods. We also thank the following organisations for their contributions to different aspects of the study: Medical Research Council (MRC) Porton Down Research Liaison Group, Porton Down Veterans Support Group, MoD Veterans Policy Unit, Defence Science and Technology Laboratory at Porton Down, National Health Service Central Register, General Register Office for Scotland, Office for National Statistics, and Department for Work and Pensions. Figure 1 was originally generated with an applet developed by Peter Rodgers, University of Kent, and Stirling Chow, University of Victoria, Canada: www.cs.kent.ac.uk/people/staff/pjr/EulerVennCircles/EulerVennApplet.html. Figures 2-4 were originally plotted by Adrian Goodill, Cancer Epidemiology Unit, University of Oxford.

  • Contributors: KMV and LMC jointly led the study and are guarantors. All authors participated in the study design, plan of analysis, interpretation of the results, and drafting of the paper. LL carried out the statistical analyses.

  • Funding: This study was funded by the MRC with funds provided to it by the MoD. Additional funds were provided by the Department of Public Health and Nuffield College, University of Oxford. The MRC set up a liaison group to oversee the progress of the study. The MoD had no role in study design, analysis, and interpretation of data. The MoD facilitated access to its archives but had no role in deciding which data were abstracted. The MoD was sent a copy of the paper for factual comment but had no role in writing the paper or in the decision to submit for publication. The universities of Oxford and London are independent of both the MRC and the MoD.

  • Competing interests: None declared.

  • Ethical approval: The study was approved by the south east multicentre research ethics committee, the Defence Medical Services clinical research committee, and the Patient Information Advisory Group.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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