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Background
High levels of rural to urban migration are a feature of most developing countries, and are thought to be associated with an increased risk of chronic non communicable diseases.
Aim
To investigate in adult rural to urban migrants in Tanzania changes in health related behaviours, BMI, lipids and blood pressure in the first 12 months following migration.
Methods
Through village key informants, men and women, aged 15 to 59, from Morogoro rural region intending to migrate to Dar es Salaam for at least 6 months were identified. Prior to migration and regularly (1 to 3 monthly) after migration, measurements were made, blood taken for lipids, and data on socio economic circumstances and aspects of life style collected by interview. For each migrant an age, sex and village matched non migrant was also assessed at baseline and 12 months later.
Results
Two hundred and nine migrants, 103 men and 106 women, had measurements prior to migration, mean age 28.0 (SD 11) and 29.5 (11) years respectively. At 12 months contact was maintained with 132 (63.2%) of the migrants. Following migration there were significant changes in diet, with migrants consuming more meat, fresh vegetables, coconut oil and margarine. Self reported regular physical activity declined, from 79% of men to 27% (95% CIs 39% to 58%) and 38% of women to 14% (7% to 36%). At 12 months migrants, compared to the non-migrants, had a higher BMI (by 0.64 kgm−2, 95% CIs 0.28 to 1.0) and serum cholesterol (0.57 mmol l−1, 0.27 to 0.88), but lower systolic (5.2 mm Hg, 1.7 to 8.5) and diastolic blood pressure (7.4 mm Hg, 5.1 to 9.7). Triglycerides were lower in migrants at 6 months (0.31 mmol l−1, 0.06 to 0.58) but not at 12 months. Multiple linear regression was used to identify predictors of change in biological variables following migration. Associations (p<0.05) were found with aspects of diet for BMI, blood pressure, cholesterol and triglycerides, and increasing BMI predicting increasing triglycerides.
Conclusion
This relatively small study of rural to urban migrants in Tanzania found changes with mixed consequences for health following migration. Despite falls in physical activity and an overall tendency to increasing weight and cholesterol, there were apparently significant falls in blood pressure and (over the first 6 months) in triglycerides. Our tentative hypothesis is that changes in diet, from one dominated by carbohydrate to one of greater diversity, lead to favourable triglyceride and blood pressure changes, but that as weight increases these changes will be reversed.