Hatem Saeed
23-02-2008, 07:33 AM
Mortality after the 2003 invasion of Iraq: a cross-sectional cluster sample survey
Background An excess mortality of nearly 100000 deaths was reported in Iraq for the period March, 2003–September, 2004, attributed to the invasion of Iraq. Our aim was to update this estimate.
Methods Between May and July, 2006, we did a national cross-sectional cluster sample survey of mortality in Iraq. 50 clusters were randomly selected from 16 Governorates, with every cluster consisting of 40 households. Information on deaths from these households was gathered.
Findings Three misattributed clusters were excluded from the final analysis; data from 1849 households that contained 12801 individuals in 47 clusters was gathered. 1474 births and 629 deaths were reported during the observation period. Pre-invasion mortality rates were 5·5 per 1000 people per year (95% CI 4·3–7·1), compared with 13·3 per 1000 people per year (10·9–16·1) in the 40 months post-invasion. We estimate that as of July, 2006, there have been 654965 (392979–942636) excess Iraqi deaths as a consequence of the war, which corresponds to 2·5% of the population in the study area. Of post-invasion deaths, 601027 (426369–793663) were due to violence, the most common cause being gunfire.
Interpretation The number of people dying in Iraq has continued to escalate. The proportion of deaths ascribed to coalition forces has diminished in 2006, although the actual numbers have increased every year. Gunfire remains the most common cause of death, although deaths from car bombing have increased.
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Introduction
There has been widespread concern over the scale of Iraqi deaths after the invasion by the US-led coalition in March, 2003. Various methods have been used to count violent deaths, including hospital death data from the Ministry of Health, mortuary tallies, and media reports.1,2 The best known is the Iraq Body Count, which estimated that, up to September 26, 2006, between 43491 and 48283 Iraqis have been killed since the invasion.1 Estimates from the Iraqi Ministry of the Interior were 75% higher than those based on the Iraq Body Count from the same period.2 An Iraqi non-governmental organisation, Iraqiyun, estimated 128000 deaths from the time of the invasion until July, 2005, by use of various sources, including household interviews.3
The US Department of Defence keeps some records of Iraqi deaths, despite initially denying that they did.4 Recently, Iraqi casualty data from the Multi-National Corps-Iraq (MNC-I) Significant Activities database were released.5 These data estimated the civilian casuality rate at 117 deaths per day between May, 2005, and June, 2006, on the basis of deaths that occurred in events to which the coalition responded. There also have been several surveys that assessed the burden of conflict on the population.6–8 These surveys have predictably produced substantially higher estimates than the passive surveillance reports.
Aside from violence, insufficient water supplies, non-functional sewerage, and restricted electricity supply also create health hazards.9,10 A deteriorating health service with insecure access, and the flight of health professionals adds further risks. People displaced by the on-going sectarian violence add to the number of vulnerable individuals. In many conflicts, these indirect causes have accounted for most civilian deaths.11,12
In 2004, we did a survey of 33 randomly selected clusters of 30 households with a mean of eight residents throughout Iraq to determine the excess mortality during the 17·8 months after the 2003 invasion.8 The survey estimated excess mortality of at least 98000 (95% CI 8000–194000) after excluding, as an outlier, the high mortality reported in the Falluja cluster. Over half of excess deaths recorded in the 2004 study were from violent causes, and about half of the violent deaths occurred in Falluja.
To determine how on-going events in Iraq have affected mortality rates subsequently, we repeated a national household survey between May and July, 2006. We measured deaths from January, 2002, to July, 2006, which included the period of the 2004 survey.
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Methods
Participants and procedures
To measure mortality we did a national cross-sectional cohort study of deaths from January, 2002, through July, 2006. Household information was gathered about deaths that occurred between January 1, 2002, and the invasion of March 18, 2003, in all households and these data were compared with deaths that occurred from the time of the invasion through to the date of survey. A sample size of 12000 was calculated to be adequate to identify a doubling of an estimated pre-invasion crude mortality rate of 5·0 per 1000 people per year with 95% confidence and a power of 80%, and was chosen to balance the need for robust data with the level of risk acceptable to field teams. Sampling followed the same approach used in 2004,8 except that selection of survey sites was by random numbers applied to streets or blocks rather than with global positioning units (GPS), since surveyors felt that being seen with a GPS unit could put their lives at risk. The use of GPS units might be seen as targeting an area for air strikes, or that the unit was in reality a remote detonation control. By confining the survey to a cluster of houses close to one another it was felt the benign purpose of the survey would spread quickly by word of mouth among households, thus lessening risk to interviewers.
As a first stage of sampling, 50 clusters were selected systematically by Governorate with a population proportional to size approach, on the basis of the 2004 UNDP/Iraqi Ministry of Planning population estimates (table 1). At the second stage of sampling, the Governorate's constituent administrative units were listed by population or estimated population, and location(s) were selected randomly proportionate to population size. The third stage consisted of random selection of a main street within the administrative unit from a list of all main streets. A residential street was then randomly selected from a list of residential streets crossing the main street. On the residential street, houses were numbered and a start household was randomly selected. From this start household, the team proceeded to the adjacent residence until 40 households were surveyed. For this study, a household was defined as a unit that ate together, and had a separate entrance from the street or a separate apartment entrance.
Click to enlarge image
Figure 4. Trends in number of deaths reported by the Iraq Body Count and the MultiNational Corps-Iraq and the mortality rates found by this study
Mortality rates from violent causes have increased every year post-invasion. By mid-year 2006, 91 violent deaths had occurred in 6 months, compared with 27 post-invasion in 2003 and 77 in 2004, and 105 for 2005, suggesting that violence has escalated substantially. The attributed cause of these deaths has also changed with time. Our data show that gunfire is the major cause of death in Iraq, accounting for about half of all violent deaths. Deaths from air strikes were less commonly reported in 2006 than in 2003–04, but deaths from car explosions have increased since late 2005. The proportion of violent deaths attributed to coalition forces might have peaked in 2004; however, the actual number of Iraqi deaths attributed to coalition forces increased steadily through 2005. Deaths were not classified as being due to coalition forces if households had any uncertainty about the responsible party; consequently, the number of deaths and the proportion of violent deaths attributable to coalition forces could be conservative estimates. Distinguishing criminal murders from anti-coalition force actions was not possible in this survey.
Across Iraq, deaths and injuries from violent causes were concentrated in adolescent to middle age men. Although some were probably combatants, a number of factors would expose this group to more risk—eg, life style, automobile travel, and employment outside the home. The circumstances of a number of deaths from gunshots suggest assassinations or executions. Coalition forces have been reported as targeting all men of military age.27,28
From January, 2002, until the invasion in 2003, virtually all deaths in Iraq were from non-violent causes. The main causes of non-violent deaths were much the same as the leading causes of hospital deaths reported by the Ministry of Health in 2004 and 2005 (unpublished data). Death rates from non-violent causes remained essentially unchanged from pre-invasion levels until 2006, when they rose by 2·0 deaths per 1000 per year above the pre-invasion baseline, an increase that was not significant. We are unsure of the reason for the observed change in sex ratio of adults aged 15–59 years dying from non-violent causes between pre-invasion and post-invasion periods (table 2), or why deaths from cardiovascular causes rose after the invasion.
All surveys have potential for error and bias. The extreme insecurity during this survey could have introduced bias by restricting the size of teams, the number of supervisors, and the length of time that could be prudently spent in all locations, which in turn affected the size and nature of questionnaires. Further, calling back to households not available on the initial visit was felt to be too dangerous. Families, especially in households with combatants killed, could have hidden deaths. Under-reporting of infant deaths is a wide-spread concern in surveys of this type.29,30 Entire households could have been killed, leading to a survivor bias. The population data used for cluster selection were at least 2 years old, and if populations subsequently migrated from areas of high mortality to those with low mortality, the sample might have over-represented the high-mortality areas. The miscommunication that resulted in no clusters being interviewed in Duhuk and Muthanna resulted in our assuming that no excess deaths occurred in those provinces (with 5% of the population), which probably resulted in an underestimate of total deaths. Families could have reported deaths that did not occur, although this seems unlikely, since most reported deaths could be corroborated with a certificate. However, certificates might not be issued for young children, and in some places death certificates had stopped being issued; our 92% confirmation rate was therefore deemed to be reasonable.
Large-scale migration out of Iraq could affect our death estimates by decreasing population size. Out-migration could introduce inaccuracies if such a process took place predominantly in households with either high or low violent death history. Internal population movement would be less likely to affect results appreciably. However, the number of individual households with in-migration was much the same as those with out-migration in our survey.
Although interviewers used a robust process for identifying clusters, the potential exists for interviewers to be drawn to especially affected houses through conscious or unconscious processes. Although evidence of this bias does not exist, its potential cannot be dismissed.31 Furthermore, families might have misclassified information about the circumstances of death. Deaths could have been over or under-attributed to coalition forces on a consistent basis. The numbers of non-violent deaths were low, thus, estimation of trends with confidence was difficult. Not sampling two of the Governorates could have underestimated the total number of deaths, although these areas were generally known as low-violence Governorates. Finally, the sex of individuals who had died might not have been accurately reported by households. Female deaths could have been under-reported, or there might have been discomfort felt in reporting certain male deaths.
The striking similarity between the 2004 and 2006 estimates of pre-war mortality diminishes concerns about people's ability to recall deaths accurately over a 4-year period. Likewise, the similar patterns of mortality over time documented in our survey and by other sources corroborate our findings about the trends in mortality over time.1,5,32
In Iraq, as with other conflicts, civilians bear the consequences of warfare. In the Vietnam war, 3 million civilians died; in the Democratic Republic of the Congo, conflict has been responsible for 3·8 million deaths; and an estimated 200000 of a total population of 800000 died in conflict in East Timor.33–35 Recent estimates are that 200000 people have died in Darfur over the past 31 months.36 We estimate that almost 655000 people—2·5% of the population in the study area—have died in Iraq. Although such death rates might be common in times of war, the combination of a long duration and tens of millions of people affected has made this the deadliest international conflict of the 21st century, and should be of grave concern to everyone.
At the conclusion of our 2004 study8 we urged that an independent body assess the excess mortality that we saw in Iraq. This has not happened. We continue to believe that an independent international body to monitor compliance with the Geneva Conventions and other humanitarian standards in conflict is urgently needed. With reliable data, those voices that speak out for civilians trapped in conflict might be able to lessen the tragic human cost of future wars.
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Contributors
G Burnham, as principal investigator, was involved in the study design and ethical approval, took part in the analysis and interpretation of results, and led the writing of the paper. R Lafta managed the field survey in Iraq, participated in the study design and the analysis, interpretation, and preparation of the manuscript. S Doocy managed the study data and was involved in the analysis, interpretation, and the writing of the manuscript. L Roberts instigated the study and assisted with the analysis and interpretation of the data and the writing of the manuscript.
Conflict of interest statement
We declare that we have no conflict of interest.
Acknowledgments
We acknowledge the assistance of Scott Zeger in the study design and analysis, Elizabeth Johnson in the statistical analysis, Courtland Robinson and Stan Becker who helped with the demographic analysis, and Elizabeth Dzeng who assisted with data management. We express our deepest admiration for the dedicated Iraqi data collectors who have asked not to be identified. Funding was provided by the Massachusetts Institute of Technology and the Center for Refugee and Disaster Response of the Johns Hopkins Bloomberg School of Public Health.
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