Medical imaging utilization in migrants compared with nonmigrants in a universal healthcare system: A population-based matched cohort study

Abstract

Background: Medical imaging is an integral part of healthcare. Globalization has resulted in increased mobilization of migrants to new host nations. The association between migration status and utilization of medical imaging is unknown.

Methods and findings: A retrospective population-based matched cohort study was conducted in Ontario, Canada from April 1, 1995 to December 31, 2016. A total of 1,848,222 migrants were matched 1:1 to nonmigrants in the year of migration on age, sex, and geography. Utilization of computed tomography (CT), magnetic resonance imaging (MRI), radiography, and ultrasonography was determined. Rate differences per 1,000 person-years comparing migrants to nonmigrants were calculated. Relative rates were calculated using a recurrent event framework, adjusting for age, sex, and time-varying socioeconomic status, comorbidity score, and access to a primary care provider. Estimates were stratified by migration age: children and adolescents (≤19 years), young adults (20 to 39), adults (40 to 59), and older adults (≥60). Utilization rates of CT, MRI, and radiography were lower for migrants across all age groups compared with Ontario nonmigrants. Increasing age at migration was associated with larger differences in utilization rates. Older adult migrants had the largest gap in imaging utilization. The longer the time since migration, the larger the gap in medical imaging use. In multivariable analysis, the relative rate of imaging was approximately 20% to 30% lower for migrants: ranging from 0.77 to 0.88 for CT and 0.72 to 0.80 for MRI imaging across age groups. Radiography relative rates ranged from 0.84 to 0.90. All migrant age groups, except older adults, had higher rates of ultrasonography. The indication for imaging was not captured, thus it was not possible to determine if the imaging was necessary.

Conclusions: Migrants utilized less CT, MRI, and radiography but more ultrasonography. Older adult migrants used the least amount of imaging compared with nonmigrants. Future research should evaluate whether lower utilization is due to barriers in healthcare access or health-seeking behaviors within a universal healthcare system.

Fig 1. Mean cumulative number of recurrent imaging events stratified by age at migration with accompanying 95% CIs.

Adjusted for baseline matching variables: age, sex, index year, and geographical area. Index is the migration date for the migrant cohort and the dummy migration date for matched individuals.

Fig 2. Overall incidence rate and absolute rate difference of medical imaging utilization for migrants compared with nonmigrants with accompanying 95% CIs.

Incidence rate and rate difference values per 1,000 person-years. Rate difference was calculated as the absolute difference between migrants and nonmigrants. Dashed lined represents a null effect of the rate difference. Adjusted for baseline matching variables: age, sex, index year, and geographical area.

Fig 3. Incidence rate and absolute rate difference of medical imaging utilization by elapsed time since migration with accompanying 95% CIs.

Incidence rate and rate difference values per 1,000 person-years. Rate difference was calculated as the absolute difference between migrants and nonmigrants. Dashed lined represents a null effect of the rate difference. Adjusted for baseline matching variables: age, sex, index year, and geographical area.