LAST week, the medical journal The Lancet published the findings of an important study of deaths in Iraq. President George Bush and Prime Minister Howard were quick to dismiss its methods as discredited and its findings as not credible or believable. We beg to differ: the study was undertaken by respected researchers assisted by one of the world's foremost biostatisticians. Its methodology is sound and its conclusions should be taken seriously.

Professor Gilbert Burnham and colleagues from the Johns Hopkins Bloomberg School of Public Health in Baltimore and Al Mustansiriya University School of Medicine in Baghdad measured deaths in Iraq between January 2002 and July 2006. They surveyed 12,801 individuals in 1849 households in 47 representative clusters across the country.

Their study is important in providing the only up-to-date, independent, and comprehensive scientific study of mortality after the 2003 invasion and occupation of Iraq. The study found that mortality had risen alarmingly since March 2003 and continues to rise. The number of conflict-related excess deaths, above and beyond those that would normally occur, was estimated at 655,000. While precision about such figures is difficult, we can be confident that the excess deaths were above 390,000, and may in fact be as high as 940,000. The vast majority (92 per cent) of the excess deaths were due to direct violence.

The cross-sectional household cluster sample survey method used is a standard, robust, well-established method for gathering health data. A copy of a death certificate was available for a high proportion (92 per cent) of deaths. Conservative assumptions were made about deaths of uncertain cause and about the small areas not sampled.

Except in situations of highly reliable, well-maintained, comprehensive vital statistics collection — clearly not the case in Iraq at present — such surveys have been repeatedly demonstrated to be the best method for establishing population rates for key health indicators such as deaths, disability and immunisation coverage. Where passive information collection (such as death counts in morgues or hospitals) are incomplete, as is the case in Iraq today, population-based survey methods can be expected to find higher rates — often considerably higher — but that more accurately reflect the true situation.

Conducting such a rigorous study within the constraints of the security situation in Iraq is dangerous and difficult, and deserves commendation. We have not heard any legitimate reason to dismiss its findings. It is noteworthy that the same methodology has been used in recent mortality surveys in Darfur and Democratic Republic of Congo, but there has been no criticism of these surveys.

The study by Burnham and his colleagues provides the best estimate of mortality to date in Iraq that we have, or indeed are ever likely to have.

We urge open and constructive debate, rather than ill-informed criticism of the methods or results of sound science. All of us should consider the implications of the dire and deteriorating health situation in Iraq.

THE SIGNATORIES

Professor James A Angus, dean, faculty of medicine, dentistry and health sciences, University of Melbourne

Professor Bruce Armstrong AM, director of research, Sydney Cancer Centre; professor of public health and medical foundation fellow, University of Sydney

Dr Jim Black, head of epidemiology, Victorian Infectious Diseases Service

Professor Peter Brooks, executive dean, faculty of health sciences, University of Queensland

Professor Jonathan Carapetis, director, Menzies School of Health Research, Darwin

Dr Ben Coghlan, medical epidemiologist, Centre for International Health, Burnet Institute

Professor Mike Daube, professor of health policy, Curtin University

Associate Professor Peter Deutschmann, executive director, Australian International Health Institute, University of Melbourne

Associate Professor Trevor Duke, Centre for International Child Health, department of pediatrics, University of Melbourne

Professor Adele Green AC, deputy director, Queensland Institute of Medical Research

Associate Professor Heath Kelly, head, epidemiology unit, Victorian Infectious Diseases Reference Laboratory

Professor Stephen Leeder AO, co-director, Menzies Centre for Health Policy; professor of public health and community medicine, University of Sydney; chairman, Policy and Advocacy Group, Australasian Faculty of Public Health Medicine

Professor Alan Lopez, head, School of Population Health; professor of medical statistics and population health, University of Queensland

Professor John Mathews AM, professorial fellow, School of Population Health, University of Melbourne

Professor A. J. McMichael, director, National Centre for Epidemiology and Population Health, ANU

Dr Cathy Mead PSM, president, Public Health Association of Australia, Canberra

Professor Rob Moodie, chief executive, Victorian Health Promotion Foundation

Professor Kim Mulholland, infectious disease epidemiology unit, London School of Hygiene and Tropical Medicine, UK

Professor Terry Nolan, head, School of Population Health, Melbourne University

Associate Professor Tilman Ruff, Nossal Institute for Global Health, University of Melbourne; president, Medical Association for Prevention of War

Associate Professor Peter Sainsbury, school of public health, University of Sydney

Dr Tony Stewart, medical epidemiologist, Centre for International Health, Burnet Institute

Professor Richard Taylor, professor of international health; head, division of international and indigenous health, School of Population Health, University of Queensland; director, Australian Centre for International and Tropical Health and Nutrition

Associate Professor Mike Toole, head, Centre for International Health, Burnet Institute

Associate Professor Paul J. Torzillo AM, University of Sydney; senior respiratory physician, Royal Prince Alfred Hospital, Sydney; clinical director, respiratory and critical care services, Central Sydney Area Health Service

Dr Sue Wareham OAM, immediate past president, Medical Association for Prevention of War, Canberra

Professor Anthony Zwi, School of Public Health and Community Medicine, associate dean (international), faculty of medicine, NSW University