Objective: To examine whether insulin resistance and metabolic syndrome are associated with pre-hypertension, a new stage developed by the Joint National Committee on Prevention, Detection, Education and Treatment of High Blood Pressure (JNC-7).
Patients and methods: Subjects included 506 Japanese taking no anti-hypertensive medication. Subjects were divided into three groups according to blood pressure status using the JNC-7 criteria. Normotension (NTN) was defined as a Systolic Blood Pressure (SBP) < 120 mmHg and a Diastolic Blood Pressure (DBP) < 80 mmHg, pre-hypertension (PHT) as a SBP 120-139 mmHg or a DBP 80-89 mmHg and hypertension (HTN) as a SBP > or = 140 mmHg or a DBP > or = 90 mmHg. The metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III as modified for waist circumference criteria by the Regional Office for the Western Pacific Region of WHO. Insulin sensitivity was assessed by plasma glucose and insulin concentrations obtained at fasting or during a 75 g oral glucose tolerance test.
Results: There were no differences with respect to age, gender or glucose intolerance status among the three groups. The mean values of body mass index were similar between NTN and PHT, but were significantly higher in HTN than in other groups. The prevalence of the metabolic syndrome was 9.9% in NTN, 19.2% in PHT and 35.5% in HTN, respectively. The prevalence increased linearly with worsening of blood pressure status (p < 0.0001). An increase in the number of metabolic syndrome components (MS score) was also associated with a progress in blood pressure status. Even in the non-obese persons, the prevalence of the metabolic syndrome and the MS score increased linearly with worsening in blood pressure status. The homeostasis model assessment of insulin resistance (HOMA-R) was significantly higher in PHT and HTN than in NTN and increased significantly with worsening in blood pressure status. Furthermore, the quantitative insulin sensitivity check index (QUICKI) and the insulin sensitivity index proposed by Stumvoll et al. decreased significantly with worsening in blood pressure status.
Conclusions: The metabolic syndrome is prevalent even in the pre-hypertensive stage in a Japanese population and insulin resistance contributes to the underlying mechanisms of these abnormalities.