Introduction: Sedentary lifestyle and energy rich food have been associated with the risk of developing type 2 diabetes; limited data are available on environmental conditions in childhood on this risk later in life. The objective was to study if residency in the first 20 years of life affected the risk of developing type 2 diabetes.
Methods: In a cohort of 17811 men (48%) and women, mean age 53 years (range 33-81) participating in the population-based Reykjavík Study from 1967-91, 29% grew up in rural and 35% in coastal areas for an average of 20 years before moving to urban Reykjavík, but 36% lived in Reykjavík from birth. The prevalence of type 2 diabetes according to residency in early life was examined.
Results: The relative risk of developing type 2 diabetes was 43% lower in men (RR 0.57; 95% CI 0.43-0.77) and 26% lower (RR 0.74; 95% CI 0.56-0.99) in women living in rural areas for the first 20 years of their life compared with those living in urban Reykjavík from birth. The low prevalence among those that grew up in rural areas was maintained through the age categories of 55-64 years and 65 years and older.
Conclusions: Our findings indicate that persons growing up in rural areas in early 20th century Iceland had lower risk of developing type 2 diabetes later in life when compared with peers living in Reykjavík from birth. We postulate a prolonged effect of early development on glucose metabolism and risk of developing type 2 diabetes.
Keywords: cohort study; type 2 diabetes; Reykjavík Study; rural area; urban area; long term risk evaluation of type 2 diabetes.