Fasting plasma insulin is associated with metabolic syndrome in farmers but not in nomads among the Mongolian population, China.

The World Health Organization (WHO) includes insulin resistance among its criteria for diagnosing metabolic syndrome (MetS); however, previous epidemiologic studies have limited their research to settled populations only. This study aims to clarify the relationship between plasma insulin and metabolic factors on a broader scale by studying data obtained from nomadic and settled Mongolian populations. A cross-sectional epidemiologic study of 200 nomads and 256 farmers was performed in Inner Mongolia, Republic of China. Plasma insulin levels and other metabolic factors, such as blood pressure, serum lipids and obesity, were measured. Participants were classified into 3 categories according to their plasma insulin levels. Cut-off values grouped into tertiles of fasting insulin for all participants were 6.73 nmol/L and 10.33 nmol/L. The mean number of metabolic risk factors, waist circumference, fasting plasma glucose and triglyceride were higher, and the mean HDL cholesterol was lower in the higher fasting insulin tertile among farmers after adjusting for age, gender, smoking, alcohol drinking and total cholesterol. However, no MetS factors were statistically related with fasting insulin tertile levels among nomads. In nomads, hyperinsulinemia may not be an indicator of MetS due to their specific life-style.