Fasting insulin in relation to subsequent blood pressure changes and hypertension in women

The role of hyperinsulinemia in the development of hypertension is not well understood, particularly insofar as both conditions relate to obesity. The present analysis examines the hypothesis that hyperinsulinemia, independent of obesity, precedes hypertension and natural blood pressure increases in women. The subjects were 50-year-old women from a prospective population study in Gothenburg, Sweden. Fasting insulin levels were determined at baseline (1968-1969) and were evaluated in relation to subsequent hypertension. Blood pressures were measured at the initial physical examination and at the 6- and 12-year follow-up examinations. The first analysis presented here (n = 278) identified incident cases of hypertension during the 12-year follow-up period, whereas the second analysis (n = 219) examined continuous changes in blood pressure. In both analyses, degree, type, and changes in obesity were considered as possible confounding factors. High fasting insulin values were predictive of subsequent incidence of hypertension over the 12-year follow-up period. Subjects with insulin values above the 75th percentile experienced three times more hypertension than did those below the 25th percentile. There was also a significant association between insulin at baseline and increases in diastolic (but not systolic) blood pressure. The positive relations between fasting insulin, on one hand, and diastolic blood pressure changes and hypertension, on the other, could not be explained by confounding effects of body mass index, waist/hip ratio, or weight gain. These findings are consistent with the hypothesis that fasting insulin levels may be one predisposing factor in the etiology of hypertension.