Can the salmon bias effect explain the migrant mortality advantage in England and Wales?

Matthew Wallace; Hill Kulu

doi:10.1002/psp.2146

Impact of Occupation and Family Burden on Psychological Adjustment in Returning Migrants

Global Clinical and Translational Research ◽

10.36316/gcatr.02.0026 ◽

2020 ◽

pp. 16-26

Author(s):

TingTing Wang ◽

Jianfa Shen ◽

Wenfei Wang ◽

YU Zhu

Keyword(s):

Mental Health ◽

General Health Questionnaire ◽

Family Burden ◽

Urban Migration ◽

Cross Sectional Survey ◽

Bias Effect ◽

Social Dysfunction ◽

Cross Sectional ◽

Salmon Bias ◽

General Linear Regression Model

Background: Recently, increasing returning migrants in China accompany the massive rural-urban migration, but little information on mental health is available. Methods: A cross-sectional survey was conducted in 2,100 households from seven provinces to examine the effect of return migration on mental health and its association with entrepreneurial experience, occupation, and family burden compared with local rural non-migrants. The 12-item General Health Questionnaire (GHQ-12) was used to measure mental health status, and factor scores were extracted through factor analysis to gauge three sub-domains of loss of confidence, social dysfunction, and anxiety. A general linear regression model was used to analyze the data for the association. Results: Returning migrants were more likely to have elevated levels of anxiety compared with rural non-migrants when adjusting for social and demographic variables. Entrepreneurial experiences reduced loss of confidence and social dysfunction but increased anxiety; started but not currently running a business, and having older adults at home to care seemed growing concern in returning migrants but not in the rural non-migrants. Conclusion: Our study supports the salmon bias effect, but that occupation, entrepreneurship, and family burden may have non-negligible impacts on the anxiety in returning migrants. The findings may have implications for promoting social integration for returning migrants.

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Salmon bias effect as hypothesis of the lower mortality rates among immigrants in Italy

Scientific Reports ◽

10.1038/s41598-021-87522-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Anteo Di Napoli ◽

Alessandra Rossi ◽

Gianfranco Alicandro ◽

Martina Ventura ◽

Luisa Frova ◽

...

Keyword(s):

Mortality Rate ◽

Country Of Origin ◽

Mortality Rates ◽

Mortality Data ◽

Bias Effect ◽

Salmon Bias ◽

Lower Socioeconomic ◽

National Cohort ◽

The Difference ◽

Standardized Mortality Rate

AbstractCompared with natives, immigrants have lower all-cause mortality rates, despite their lower socioeconomic status, an epidemiological paradox generally explained by the healthy migrant effect. Another hypothesis is the so-called salmon bias effect: “statistically immortal” subjects return to their country of origin when they expect to die shortly, but their deaths are not registered in the statistics of the country of residence. This underestimation of deaths determines an artificially low immigrant mortality rate. We aimed to estimate the potential salmon bias effect on differences in mortality rates between Italians and immigrants. We used a national cohort of all Italians registered in the 2011 census and followed up for mortality from 2012 to 2016. Mortality data were retrieved from the Causes of Death Register, which included all deaths occurring in the country and the Resident Population Register, which collects also the deaths occurring abroad. We assumed as a possible salmon bias event the death of an immigrant resident in Italy that died in his/her country of origin. Considering the deaths occurring in the country of origin, we observed an 18.1% increase in the overall mortality rates for immigrants and an increase of 23.7% in the age-standardized mortality rate. Mortality rates of immigrants resident in Italy, calculated without taking into account the deaths occurring in the country of origin, are certainly underestimated. However, the salmon bias only partly explains the difference in mortality rates between immigrants and Italians.

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