The Effect of Urbanization on Insulin Resistance

Purpose Cardiovascular disease (CVD) is of growing concern in South Asia and has developed alongside rapid urbanization. India, in particular, shoulders a heavy burden of CVD yet little is known of the relationship between CVD... [ view full abstract ]

Purpose
Cardiovascular disease (CVD) is of growing concern in South Asia and has developed alongside rapid urbanization. India, in particular, shoulders a heavy burden of CVD yet little is known of the relationship between CVD and changes in the built environment. We hypothesized that urbanization would be associated with insulin resistance (IR), a major underlying abnormality driving CVD, in a cohort of adults in India.

Methods
The PURSE-HIS study was designed to investigate the prevalence and progression of CVD and its risk factors. Participants over 20 years of age were recruited from India Census designated urban, semiurban and rural areas in the state of Tamil Nadu. Participant residences were geocoded and used to assign MODIS satellite-derived land cover and Euclidian distance from urban center as measures of urbanization. IR was defined by homeostasis model assessment of IR (HOMA-IR) in the highest quartile. Our analysis excluded participants with diabetes. Separate models for men and women were adjusted for age, anxiety, BMI, physical activity, stress, socioeconomic status and energy intake (N= 1766).

Results
Distance from urban center was significantly associated with an increased odds of IR for both genders. A distance of <20km resulted in an OR of 2.1 (95%CI: 1.5-3.0) for males and 1.7 (95%CI: 1.3-2.2) for females compared to the referent group (61-80km). Urban land cover was associated with an OR of 1.3 (95%CI: 1.1-1.5) for females only, while a Census designation of urban/semiurban was associated with an OR of 1.4 (95%CI: 1.1-1.7) for males.

Conclusions
Participants residing in urban or semi-urban areas had increased risk of IR. Differences were found based on gender and with metrics of urbanization. Urbanization as an independent predictor of IR indicates that changes in built environment may explain increases in CVD incidence in India and other rapidly urbanizing countries in South Asia.