Norredam Marie, Hansen Oluf Hoejbjerg, Petersen Jørgen Holm, Kunst Anton E, Kristiansen Maria, Krasnik Allan, Agyemang Charles
1 Section for Health Services Research, Department of Public Health, Danish Research Centre for Migration, Ethnicity, and Health, University of Copenhagen, Copenhagen, Denmark 2 Department of Immigrant Medicine, Section of Infectious Diseases, Hvidovre Hospital, Copenhagen, Denmark
3 Section for Biostatistics, Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
Eur J Public Health. 2015 Feb;25(1):84-9. doi: 10.1093/eurpub/cku138. Epub 2014 Sep 8.
'Remigration bias' is often referred to when explaining low mortality outcomes among migrants compared with local-born. The hypothesis suggests that severely ill migrants tend to return to their country of origin, but it has hitherto not been tested in a large-scale epidemiological study. Consequently, we studied whether migrants with severe disease were more likely to emigrate compared with migrants without severe disease.
A historic prospective cohort study was conducted based on all adult refugees and family reunification immigrants (n = 114,331) who obtained residence permission in Denmark between 1 January 1993 and 31 December 2010. Migrants with severe disease were identified through the Danish National Patient Register. Emigrations during follow-up (1 January 1993 to 31 December 2011) were identified using the Danish Civil Registration System. Hazard ratios were calculated for emigration among migrants with different levels of disease severity, adjusting for sex, age and income.
Results showed progressively fewer emigrations with increasing disease severity. Migrants with low (HR = 0.92; 95% CI: 0.80-1.06), moderate (HR = 0.84; 95% CI: 0.67-1.06) and high (HR = 0.70; 95% CI: 0.55-0.90) disease severity had fewer emigrations to 'country of origin' compared with migrants without disease. For emigration to 'any country', results likewise showed fewer emigrations among migrants with low (HR = 0.86; 95% CI: 0.78-0.95), moderate (HR = 0.73; 95% CI: 0.62-0.87) and high (HR = 0.64; 95% CI: 0.53-0.76) disease severity. This tendency was also observed by nationality and migrant status. On the disease-specific level, no uniform tendencies in emigration patterns were identified.
The results do not generally support the hypothesis of 'remigration bias' but rather suggest the opposite. Accordingly, remigration bias does not appear to explain lower mortality of migrants.
在解释移民与本地出生者相比死亡率较低的结果时，经常会提到“回迁偏差”。该假设认为，重病移民往往会返回其原籍国，但迄今为止尚未在大规模流行病学研究中得到验证。因此，我们研究了与无严重疾病的移民相比，患有严重疾病的移民是否更有可能移民。
基于1993年1月1日至2010年12月31日期间在丹麦获得居住许可的所有成年难民和家庭团聚移民（n = 114,331）进行了一项历史性前瞻性队列研究。通过丹麦国家患者登记册识别患有严重疾病的移民。使用丹麦民事登记系统确定随访期间（1993年1月1日至2011年12月31日）的移民情况。计算不同疾病严重程度的移民的移民风险比，并对性别、年龄和收入进行调整。
结果显示，随着疾病严重程度的增加，移民人数逐渐减少。与无疾病的移民相比，疾病严重程度低（HR = 0.92；95% CI：0.80 - 1.06）、中度（HR = 0.84；95% CI：0.67 - 1.06）和高度（HR = 0.70；95% CI：0.55 - 0.90）的移民返回“原籍国”的人数较少。对于移民到“任何国家”，结果同样显示，疾病严重程度低（HR = 0.86；95% CI：0.78 - 0.95）、中度（HR = 0.73；95% CI：0.62 - 0.87）和高度（HR = 0.64；95% CI：0.53 - 0.76）的移民人数较少。按国籍和移民身份也观察到了这种趋势。在疾病特异性层面，未发现移民模式的统一趋势。
结果总体上不支持“回迁偏差”的假设，反而表明情况相反。因此，回迁偏差似乎无法解释移民较低的死亡率。
