Sampling flaws may have inflated Lancet's Gaza mortality survey death toll, researchers argue

Released by Professor Emeritus Sergio DellaPergola of the Hebrew University of Jerusalem and independent researcher Mark Zlochin, the correspondence analyzed the survey's publicly released data.

The widely cited Gaza Mortality Survey, published in The Lancet Global Health, may be more unreliable than previously assumed, according to new correspondence recently published in the British medical journal.

Released by Professor Emeritus Sergio DellaPergola of the Hebrew University of Jerusalem and independent researcher Mark Zlochin, the correspondence analyzed the survey's publicly released data and found several discrepancies in its methodology and study sample.

According to the Gaza Mortality Survey, some 75,200 violent deaths have occurred in Gaza during the Israel-Hamas War, which started on October 7, 2023.

However, DellaPergola and Zlochin argue that the population sample used by researchers in the survey was inaccurate.

They note that the results from two of the interviewer teams, Gaza9 and Gaza3, are extreme outliers that diverge materially from those of the remaining teams.

One-quarter of violent deaths claimed by only eight percent of sample

Gaza9, for example, reported on 100 out of 393 (roughly one-quarter) violent deaths, while surveying only eight percent of the total sample. Both Gaza9 and Gaza3 also exhibited different demographic structures from the remaining teams, including having lower populations of children and smaller mean household sizes.

Population-level mortality estimates are only as reliable as the representativeness of the underlying sample, DellaPergola said. Our analysis raises important questions regarding whether the survey achieved the level of representativeness necessary to support its national mortality estimates.

Other anomalies in the recorded data included survey teams covering only small portions of the areas allocated to them, discrepancies in the estimates of Gazan prisoners, and quality-control procedures not catching any of the aforementioned issues.

Medical journal's history of anti-Israel publications

This is not the first time that The Lancet has come under fire for its publication of articles relating to Israel.

Earlier this month, The Lancet published a petition calling for the suspension of the Israel Medical Association (IMA) from the World Medical Association (WMA).

The petition was created by health organizations such as the People's Health Movement (PHM), Artsen voor Gaza (Doctors for Gaza), and the Health Advisory Council of the Jewish Voice for Peace calling for the IMA to be suspended from the WMA over its failure to speak out against the genocide of Palestinians, the destruction of health-care infrastructure, and the torture and killing of health-care workers in Gaza.

In July 2024, the medical journal also published a piece authored by doctors Rasha Khatib, Martin McKee, and Salim Yusuf, which claimed that it is not implausible to estimate that up to 186,000 or even more deaths could be attributable to the current conflict in Gaza.

Despite the fact that it was designated as a correspondence or a letter to the editor rather than a peer-reviewed academic article, the article was disseminated en masse and shared by figures such as UN Special Rapporteur Francesca Albanese.

Mathilda Heller contributed to this report.