Effects of length of residency on the development of physical and mental illnesses in immigrant women in Taiwan

Objectives The majority of female immigrants who are married in Taiwan often face a variety of stresses, which may lead to physical or mental illness. Yet few studies have validated the impact of length of residency on physical and mental health using large-scale data. This study combined five nationwide databases and explored the impact of length of residency in Taiwan on the physical and mental health of female marriage immigrants. Design This is a retrospective cohort study. Setting Taiwan. Participants A total of 168 202 female immigrants, who were registered in the national health insurance database from 2001 to 2017, were enrolled for analysis. Measure The length of residency was taken as the period from their first appearance in the national health insurance database to the end of 2017. Hypertension and diabetes were chosen as indices of physical health and depression as an index of mental health. Diagnosis standards were based on the International Classification of Disease, ninth or 10th Revision. Results The physical and mental health of the immigrants deteriorated with increasing time of residence in Taiwan. Immigrants who had resided in Taiwan for 5-10 years or ≥10 years, respectively, had a 5.8-fold (95% CI: 3.46 to 9.74) or 6.29-fold (95% CI: 4.61 to 8.59) higher adjusted risk of developing hypertension; a 3.97-fold (95% CI: 2.54 to 6.21) or 9.18-fold (95% CI: 5.48 to 15.38) higher adjusted risk of developing diabetes; and a 5.01-fold (95% CI: 3.14 to 8.01) or 12.19-fold (95% CI: 8.65 to 17.18) higher adjusted risk of developing depression than their counterparts who had lived in Taiwan for ≤5 years. Conclusion These findings suggest the time elapsed since migration can be a factor in the deterioration of both physical and mental health among female marriage immigrants in Taiwan.