Article type
Year
Abstract
Background: Limited information is available about the effects of rural-to-urban within-country migration on cardiovascular (CV) risk factors in low and middle income countries (LMIC).
Objectives: We performed a systematic review of studies evaluating these effects and having rural and/or urban control groups.
Methods: Two teams of investigators independently searched observational studies published between 1960 and June 2010. Studies evaluating international migration or those from developed countries were excluded. Three investigators extracted the information stratified by gender. Wecaptured information on 17 known CV risk factors.
Results: Eighteen studies (n = 58,536) were included. Studies were highly heterogeneous with respect to age, study design, sampling frame for migrants, years of urban exposure for migrants, and reported CV risk factors. Fourteen studies were cross-sectional; only six studies adjusted for confounders. 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 when compared to therural group and usually lower or less frequent when compared to the urban group. This gradient was usually present in both males and females separately. Anthropometric (waist-to-hip ratio, hip/waist circumference, triceps skinfolds) and metabolic (fasting glucose and insulin, insulin resistance) risk factors usually followed the same gradient, but conclusions are weak due to the paucity of information. Hypertension, HDL, and other uncommonly reported risk factors such as fibrinogen and C-reactive protein did not follow any pattern among groups.
Conclusion: In LMIC, studies investigating the effect of rural-to-urban within-country migration on CV risk factors are heterogeneous. A gradient, higher or more frequent in migrants than in the rural groups but lower or less frequent than the urban groups, was observed in most but not all CV risk factors. Such gradients may or may not be associated to differential CV events and long-term evaluations remain necessary.
Objectives: We performed a systematic review of studies evaluating these effects and having rural and/or urban control groups.
Methods: Two teams of investigators independently searched observational studies published between 1960 and June 2010. Studies evaluating international migration or those from developed countries were excluded. Three investigators extracted the information stratified by gender. Wecaptured information on 17 known CV risk factors.
Results: Eighteen studies (n = 58,536) were included. Studies were highly heterogeneous with respect to age, study design, sampling frame for migrants, years of urban exposure for migrants, and reported CV risk factors. Fourteen studies were cross-sectional; only six studies adjusted for confounders. 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 when compared to therural group and usually lower or less frequent when compared to the urban group. This gradient was usually present in both males and females separately. Anthropometric (waist-to-hip ratio, hip/waist circumference, triceps skinfolds) and metabolic (fasting glucose and insulin, insulin resistance) risk factors usually followed the same gradient, but conclusions are weak due to the paucity of information. Hypertension, HDL, and other uncommonly reported risk factors such as fibrinogen and C-reactive protein did not follow any pattern among groups.
Conclusion: In LMIC, studies investigating the effect of rural-to-urban within-country migration on CV risk factors are heterogeneous. A gradient, higher or more frequent in migrants than in the rural groups but lower or less frequent than the urban groups, was observed in most but not all CV risk factors. Such gradients may or may not be associated to differential CV events and long-term evaluations remain necessary.