The effect of age on prevalence of secondary forms of hypertension in 4429 consecutively referred patients.

Objectives: To investigate the importance of age and other variables on the prevalence of secondary forms of hypertension in a hypertension referral center.

Design: Over the past 18 years 4429 patients have been referred by their physicians for a 1-day blood pressure study to investigate secondary causes of hypertension.

Methods: The 1-day blood pressure study included a history and physical examination by a physician, and measurements of serum sodium, potassium, creatinine, thyroxine, thyroid stimulating hormone, stimulated plasma renin activity, blood pressure response to the angiotensin II analogue saralasin, recumbent and upright plasma catecholamines, and plasma cortisol and aldosterone after infusion of 2 liters 0.9% saline over 3-4 h.

Results: The prevalence of secondary forms of hypertension was 10.2%, including renovascular hypertension (3.1%), primary aldosteronism (1.4%), Cushing's syndrome (0.5%), pheochromocytoma (0.3%), primary hypothyroidism (3.0%) and a serum creatinine > 2.0 mg/dl (1.8%). There was a very significantly increased prevalence with age of secondary forms of hypertension associated with renovascular hypertension, primary hypothyroidism and renal insufficiency. The concomitant presence of atherosclerosis significantly increased the prevalence of renovascular hypertension (9.5%) and renal insufficiency (8.0%).

Conclusions: Increasing age and coexisting atherosclerosis have significant effects on the prevalence of secondary forms of hypertension.