Are Holocaust survivors really at higher risk for cancer?

An interesting study claims to show that Holocaust survivors are at higher risk for all cancers:

Jewish survivors of World War II who were potentially exposed to the Holocaust are at a higher risk for cancer occurrence, according to a new study published online October 26 in the Journal of the National Cancer Institute.

Previous studies, in non-Jewish populations, investigating the relationship of cancer incidence rates to physical and psychological stress, such as famine and mental stress, have reached inclusive results.

Lital Keinan-Boker, M.D., Ph.D., MPH, of the School of Public Health, Faculty of Welfare and Health Sciences, at the University of Haifa in Israel, and colleagues compared the cancer rates in a cohort of over 300,000 Israeli Jews who were born in Europe and immigrated to Israel before or during World War II (the non-exposed group) with cancer rates in a cohort of European-born Israeli Jews who immigrated from Europe after World War II and up to 1989 (the exposed group, those potentially exposed to the Holocaust). Exposure was based on immigration dates because no individual data were available on actual Holocaust exposure.

Likely exposure, compared with non-exposure, was associated with statistically significantly increased risk for overall cancer risk (all cancers combined) for all birth cohorts, and for both sexes. The strongest associations were with breast and colorectal cancer. Earlier exposure, i.e., at a younger age, seemed to be particularly associated with increased risk of all-site cancer...

Essentially what the study seems to be claiming is that European Jews who lived through the Second World War are at higher risk than European Jews who were in Israel at the time.

This makes me a little nervous because we seem to be talking about a very wide group of people here: by 'Holocaust survivor', do they mean people who survived the death camps? Partisans in the forest? Or Jewish children living in disguise with non-Jewish families? In this study, they are all lumped together, though their experiences may have been very different.

Furthermore, many of the people in this study - in both groups - have lived through other very traumatic events: the war of 1948, the period of austerity during which food was rationed and diet affected, 1967 and the months leading up to the war, when many Israelis feared the actual destruction of their country, 1973, and the second intifadah. While none compare to the Holocaust, surely they cannot be discounted as factors affecting this kind of study, which deals with the effects of "physical and psychological stress".

Then there are the many millions of non-Jewish Europeans who lived through the Second World War, most of whom suffered severe mental stress, food deprivation etc as well (and some of whom went through the camps as well). Are the cancer statistics for the Jews who lived through the Second World War any different to the non-Jews? This highlights the problem of labelling these statistics "Holocaust-related" rather than "WWII related" - ie not knowing exactly who is included in the group "potentially exposed to the Holocaust".

In short, more investigation is needed.