The term “Genocide” was coined during the Holocaust (Bauer, 1992), referring to the murder of 6 millions Jews by the Nazis in World War 2 (1933-1945). In 1948, Genocide was defined by the United Nations Convention on the Prevention & Punishment of the Crime of Genocide as “acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group” (United Nations), and was declared an international crime.
Holocaust survivors are individuals who were persecuted by the Nazi regime but managed to escape, survive or were liberated. These individuals may have been displaced; lived in a ghetto or concentration, extermination, or forced/slave labour camps; and/or hid in occupied Nazi territory (Israeli Ministry of Finance, 2018).
As a result of this anti-Semitic persecution, there were a wide-variety of adversities among the survivors (Levav, 1998).
Two competing hypotheses arose; stating that prior exposure to genocide would either reduce (owing to resilience) versus increase (owing to vulnerabilities) the risk of physical and mental health conditions. However, the implication that being exposed to war and genocide might increase the risk of developing dementia had not been specifically explored, until now.
This study (Kodesh et al, 2019) tested the competing hypotheses that the Holocaust survivors were at reduced vs. increased (resilience vs. vulnerability) risk of dementia. The authors also stated that they would methodologically account for potential covariates relevant to the risk of dementia.
This cohort study was conducted in Israel and used an observational design. By law, every Israeli resident must join a Health Maintenance Organization (HMO) of his or her choice. This study obtained data from the Meuhedet HMO, the third largest HMO in Israel, consisting of 14% of the total population. Meuhedet is the only HMO that included data on dementia.
The sample included 51,752 individuals from the Meuhedet register, born before 1946 and who were still alive as of 1st January 2012. Participants were followed up between 1st January 2013 and 30th October, 2017. Prior to the start of the follow-up period, the authors declared that none of the cohort had a diagnosis of dementia. The mean-age of the cohort was 60.4 years.
There were strict criteria in identifying Holocaust survivors. To establish exposure to the Holocaust, the authors used the Holocaust Survivors’ Rights Authority, at the Ministry of Finance. It is the organisation responsible for implementing laws regarding survivors of the Holocaust living in Israel, granting monthly payments, medical treatments, rehabilitation and welfare services.
The presence of dementia was ascertained by a clinical diagnosis made by a geriatrician, psychiatrist and/or neurologist, that was documented in the Meuhedet register. The diagnosis was based on the criteria from ICD-9 and ICD-10.
10,781 (20.8%) individuals were classified as having been exposed to the Holocaust and 5,584 (10.8%) individuals were diagnosed with dementia during the follow-up interval.
The following covariates were chosen a priori based on their association with the exposure and/or outcome and were adjusted for:
- Demographic covariates (year of birth, sex, and city of residence)
- Diagnostic covariates (obesity, diabetes, cancer, vitamin deficiencies, concussion or head injury, migraine, depression, PTSD, sleep and schizophrenia)
- Neighbourhood socioeconomic status
- Educational attainment
- Standard of living, employment and social benefits.
Participants were stratified into holocaust-exposed and unexposed groups. Using Cox regression models, the hazard ratios for dementia and 95% confidence intervals were estimated. The hazard assumptions were then examined using Schoenfeld residuals (Therneau, 2015). The authors fitted unadjusted and adjusted models and interpreted the hazard ratios as effect sizes.
The primary results were then further explored in 12 sensitivity analyses based on the covariates measured.
The key results were:
- Of 51,752 participants:
- 1,781 (16.5%) Holocaust-exposed individuals had a dementia diagnosis,
- compared to 3,805 (9.3%) Holocaust-unexposed individuals.
- In the primary analysis (compared to the unexposed group), the model showed that the Holocaust–exposed group had:
- an estimated unadjusted hazard ratio of 1.77 (95% CI; 1.67 to 1.87)
- an adjusted hazard ratio of 1.21 ( 95% CI; 1.15 to 1.28).
- The series of sensitivity analyses replicated the result of the primary analysis. The covariates did not statistically attenuate the increased hazard ratio of dementia in the Holocaust–exposed group, compared to the Holocaust-unexposed group.
This was the first observational study to explore the association between prior exposure to genocide and the risk of dementia, with results supporting the vulnerability hypothesis.
The increased risk of dementia in those who were exposed to the Holocaust, compared to those who were unexposed, remained significant even after controlling for known confounding variables.
Strengths and limitations
Strengths of this study included:
- The strict criterion for identifying Holocaust survivors and the in-depth reports of the severe anti-Semitic European genocide, obtained by the Ministry of Finance. This limited the margin of error when collecting the cohort members
- The extensive follow-up period increased the study’s ability to capture the number of dementia cases which may have emerged over time
- There were no exclusion criteria for the sample in this study, therefore increasing the chance of identifying as many Holocaust survivors and dementia cases as possible
- The study effectively controlled for other known covariates, and conducted 12 sensitivity analyses, therefore maximising the validity of their findings.
Limitations of this study included:
- There may have been inaccuracies in detecting dementia. Holocaust survivors have been found to be more likely to report worse subjective health, compared to unexposed groups (Ohana, Golander, & Barak, 2018). Therefore, Holocaust survivors may have reported more memory issues, and therefore experience higher rates of referrals for dementia assessments
- Selective mortality was unavoidable. Holocaust survivors who were still alive at the time of the sample collection already represented the particularly “resilient” individuals
- The Meuhedet HMO is not representative of the entire population of Israel, and therefore, not all Israeli Holocaust survivors would be on the Meuhedet register.
Implications for practice
The current cost of dementia in the UK is £26 billion per year, and it is predicted to triple by 2040 (NHS England). It is estimated that 803,021 people are living with dementia in England (Alzheimer’s Society, 2019), a 14.2% increase since 2014.
While we do not have preventative or curative measures to tackle a diagnosis of dementia, it is still important for healthcare professionals to know who is at risk. Following this study, we should take into account the health implications of genocide. More consideration is required to prioritise specialist care towards the elderly exposed to genocide, such as engagement in cognitive exercise (Valenzuela & Sachdev, 2009) and targeting risk factors associated with dementia, such as depression (Deckers et al., 2015).
Statement of interests
Kodesh, A., Levav, I. and Levine, S.Z. (2019), Exposure to Genocide and the Risk of Dementia. JOURNAL OF TRAUMATIC STRESS, 32: 536-545. doi:10.1002/jts.22406
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Valenzuela, M., & Sachdev, P. (2009). Can cognitive exercise prevent the onset of dementia? Systematic review of randomized clinical trials with longitudinal follow-up. American Journal of Geriatric Psychiatry, 17, 179–187.: https://doi.org/10.1016/j.jalz.2009.05.544
United Nations: Prevent Genocide, https://www.un.org/ar/preventgenocide/adviser/pdf/osapg_analysis_framework.pdf