Context
Limited information is available of effects of rural-to-urban within-country migration on cardiovascular (CV) risk factors in low and middle income countries (LMIC).
Objective
We performed a systematic review of studies evaluating these effects and having rural and/or urban control groups.
Study Selection
Two teams of investigators searched observational studies in MEDLINE, Web of Science and Scopus until December 2010. Studies evaluating international migration were excluded.
Data Extraction
Three investigators extracted the information stratified by gender. We captured information on 17 known CV risk factors.
Results
Eighteen studies (n=58,536) were included. Studies were highly heterogeneous with respect to study design, migrant sampling frame, migrant urban exposure, and reported CV risk factors. In migrants, commonly reported CV risk factors –systolic and diastolic blood pressure, body mass index, obesity, total cholesterol, and LDL– were usually higher or more frequent than the rural group, and usually lower or less frequent than the urban group. This gradient was usually present in both genders. Anthropometric (waist-to-hip ratio, hip/waist circumference, triceps skinfolds) and metabolic (fasting glucose/insulin, insulin resistance) risk factors usually followed the same gradient, but conclusions are weak due to information paucity. Hypertension, HDL, fibrinogen and C-reactive protein did not follow any pattern.
Conclusions
In LMIC, most but not all CV risk factors have a gradient of higher or more frequent in migrants than in the rural groups but lower or less frequent than the urban groups. Such gradients may or may not be associated to differential CV events and long-term evaluations remain necessary.