Is insulin an independent risk factor for hypertension? The Paris prospective study

Background. The link between hyperinsulinaemia and hypertension has been examined in few prospective studies and often diminished after adjustment for obesity, central adiposity and baseline blood pressures. Methods. The incidence of hypertension was studied as a function of baseline insulin and glucose in 4149 Caucasian, non-hypertensive, non-diabetic middle-aged men from the Paris Prospective Study. Blood pressures were measured over the 3 years of follow-up; hypertension incidence was defined as systolic blood pressure greater than or equal to 160 mmHg or diastolic blood pressure greater than or equal to 95 mmHg or drug treatment for hypertension. Results. Pasting and 2-hour glucose and insulin were predictive of hypertension, after controlling for the known risk factors: age, excessive alcohol consumption and family history of hypertension (FHH). However, after further controlling for body mass index and central adiposity (the iliac circumference), insulin was no longer predictive in men without an FHH. When weight variation was also taken into account, and further adjustment made for baseline blood pressure and heart rate, fasting insulin, only, was predictive when the subject had a weight increase, independently of FHH. Fasting glucose was predictive of hypertension except in the case of no change or weight decrease and a negative FHH; 2-hour glucose was predictive in the presence of a positive FHH. Conclusions. Insulin and glucose levels were both risk factors for hypertension, and this risk was enhanced in the case of a positive FHH. However, obesity, especially central obesity, confounded these relationships and might be an intermediary factor in the relationship between insulin and hypertension.