title: The effect of rural-to-urban migration on renal function in an Indian population: cross-sectional data from the Hyderabad arm of the Indian Migration Study.
abstract: BACKGROUND
  Urban migration is associated with an increased risk of hypertension, obesity and diabetes in Indian migrants. This study assessed the relationship between internal migration and renal function in the Hyderabad arm of the Indian Migration Study.
  
  
  METHODS
  We assessed 841 subjects; urban non-migrants (n = 158), urban migrants (n = 424) and rural non-migrants (n = 259). Muscle mass was ascertained from DXA scanning. We derived urban life years for urban migrants and rural non-migrants. Multivariable linear regression was used to examine the association between tertiles of urban life years and 4-variable MDRD eGFR using Stata 11.
  
  
  RESULTS
  Mean eGFR was lower in urban non-migrants and urban migrants compared to rural non-migrants. The prevalence of CKD 3-5 was higher in the rural non-migrant population (5.0%) than in the urban non-migrant populations (2.5%) due to a negatively skewed distribution of eGFR in rural non-migrants. As urban life years increased, eGFR declined (p = 0.008) though there was no obvious dose response effect. After adjustment for muscle mass, the association was attenuated and the trend was consistent with chance (p = 0.08). Further adjustment for vascular risk factors weakened the association to a small degree (p = 0.11).
  
  
  CONCLUSIONS
  The high prevalence of reduced eGFR in rural areas requires further research. Urbanization was associated with reduced eGFR. This association appears mostly to be due to higher muscle mass with a small contribution from adverse vascular disease risk factors.
authors.affiliation: The Richard Bright Renal Unit, Southmead Hospital, Bristol BS10 5NB, UK. pippabailey@hotmail.com.
authors.forename: Phillippa K
authors.initials: PK
authors.lastname: Bailey
authors.forename: Charles R V
authors.initials: CR
authors.lastname: Tomson
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kinra
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
authors.forename: K V
authors.initials: KV
authors.lastname: Radhakrishna
authors.forename: Hannah
authors.initials: H
authors.lastname: Kuper
authors.forename: Dorothea
authors.initials: D
authors.lastname: Nitsch
authors.forename: Yoav
authors.initials: Y
authors.lastname: Ben-Shlomo
mesh_terms: D017677:Age Distribution; D003430:Cross-Sectional Studies; D005260:Female; D005919:Glomerular Filtration Rate; D063426:Human Migration / Q000706:statistics & numerical data*; D006801:Humans; D007194:India / Q000453:epidemiology; D007677:Kidney Function Tests / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000453:epidemiology*; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data*; D017678:Sex Distribution; D014505:Urban Population / Q000706:statistics & numerical data*; D014507:Urbanization