FASTING INSULIN LEVEL UNDERESTIMATES RISK OF NON-INSULIN-DEPENDENT DIABETES-MELLITUS DUE TO CONFOUNDING BY INSULIN-SECRETION

Fasting insulin has been used as a surrogate measure of insulin sensit ivity in studies of non-insulin-dependent diabetes mellitus (NIDDM) ri sk, but the fasting insulin-NIDDM association may be confounded by ins ulin secretion, which correlates negatively with NIDDM risk and positi vely with fasting insulin level. In a prospective 5-year study of 137 nondiabetic Japanese-American men in King County, Washington State, hi gher fasting insulin was not strongly related to NIDDM (odds ratio (OR ) - 1.37, 95% confidence interval (CI) 0.80-2.34), but this odds ratio increased substantially after adjustment for insulin secretion (OR = 2.92, 95% CI 1.41-6.06), Research on NIDDM risk in relation to fasting insulin may yield biased effect measures unless adjusted for insulin secretion.