The Holocaust was one of the most traumatic events in human history. The "systematic, bureaucratic, state-sponsored persecution and murder of six million Jews by the Nazi regime and its collaborators," as described by the United States Holocaust Memorial Museum, left survivors with physical and emotional scars to carry indefinitely.
Those include an elevated risk for cancer, according to a new study. In "Cancer Risk Among Holocaust Survivors in Israel—A Nationwide Study," published Monday in the journal Cancer, researchers from Chaim Sheba Medical Center, Tel Aviv University and Haifa University found that Holocaust survivors in Israel had "a small but consistent increase in cancer development."
During the Holocaust, eventual survivors were subjected to a litany of stressors, including starvation, extreme temperature, overcrowding, infectious diseases, intense and strenuous physical activity, and physical and emotional abuse, as well as psychological responses such as anxiety and sleep deprivation. Some of these factors have been previously linked to increased or decreased rates of cancer. Here, the researchers attempted to look at the impact of combinations of stressors as experienced by this population.
Siegal Sadetzki, head of the Cancer and Radiation Epidemiology Unit at Chaim Sheba Medical Center's Gertner Institute, and her colleagues looked at a total of 152,622 Holocaust survivors living in Israel. They used records spanning more than four decades and did two analyses using different approximations for "exposure" to the stressors, since there is no one agreed-upon definition of a "Holocaust survivor."
The main analysis used the receipt of compensation according to various laws—such as Israel's "Victims of Nazi Persecution Act" and the "Holocaust Survivors' Benefits Act"—as a proxy for exposure, comparing that group to a group of individuals who had applied for compensation as Holocaust victims but were denied. A complementary analysis split up those who were granted compensation by country of origin into those from Nazi Germany and the countries directly occupied by the regime, and those from nonoccupied countries, including those of the Axis and Allied powers and neutral nations.
Roughly 22 percent of Holocaust survivors who were granted compensation were diagnosed with cancer, the investigators found using data from the Israeli Central Population Registry and the National Cancer Registry, compared to 16 percent of those in the group denied compensation. The risk of the group granted compensation for developing any type of cancer was six percent higher. They had a 12 percent higher chance of developing colorectal cancer and a 37 percent increased risk of lung cancer. Those from occupied countries had an eight percent increased risk of developing cancer compared to their counterparts from nonoccupied countries, with higher rates of colorectal, stomach, lung and renal cancers as well as leukemia. Neither analysis showed an increased risk of breast or gynecologic cancers among women.
"The data emphasize the importance of learning about the combined effect of several exposures occurring intensely and contemporaneously on cancer risk, such as those that unfortunately occurred during World War II," Sadetzki said in a statement. "Such inspection cannot be conducted by experimental studies and could only be evaluated by using observational epidemiological surveys."
The results are not entirely surprising. A study published in 2009 in the Journal of the National Cancer Institute compared European-born Israeli Jews who immigrated after the war to those who immigrated before or during the war. Researchers found that those who remained in Europe during the war were at least 17 percent more likely to develop cancer.
"A possible explanation for the differences in cancer incidence observed among the various Jewish ethnic groups may be differences in their specific exposure to the traumas of the Holocaust," they wrote.
The authors of the new study reference the previous work, but point out that immigration times are a broad estimate of exposure. They identify their own study's strengths as including a large overall sample size, the long-term follow up and individual data on exposure and cancer diagnoses. On the other hand, their data were limited to survivors who immigrated to Israel, were still alive in 1953 and had cancers that occurred after 1960. In addition, the exposure definitions were only proxies based on legal classifications and countries of origin, rather than specific or detailed information about individuals' experiences during the Holocaust. It's also important to consider that because the comparison group in the main analysis consisted of individuals who had applied as Holocaust victims, they may have experienced some effects of the Holocaust, even if these were not sufficient to receive compensation.
"The authors really did the best they could do," based on the available data, Electra Paskett, associate director of population sciences at the Comprehensive Cancer Center of the Ohio State University, tells Newsweek. The research "gives us evidence that a horrible event imposed on an entire people has long-reaching effects on cancer," she adds. Some of the effects, she points out, could be related to behaviors like smoking that are used to cope with the stress of such events. But in any case, the study shows "the impact of things that sometimes we don't think will necessarily cause a disease many years out [like cancer], such as fear, intense fear, hunger, bad treatment, incarceration, discrimination, everything that you can think of that happened in the Holocaust."
Some elements of these experiences can also be observed in other cases. Paskett, who is also a section editor at Cancer, teamed up with two colleagues to write an editorial related to the study. In "Extreme Population-Level Events: Do They Have an Impact on Cancer?" she and her colleagues look at the effects of population-level tragedies more broadly on cancer development, including examples like country-wide famines and population-level discrimination. They suggest that Sadetzki's study "may have parallels with racial minority groups in the United States who experience serious social deprivation over time," though additional research would be needed to parse those out.
The study linking the horrors of the Holocaust to cancer risk "gets people to think about the impact of stress," she says, in both historical and contemporary contexts. "A population group can be so discriminated against and put in [such] horrible situations that the effects last for years."