Circannual variations in blood pressure, urinary catecholamine excretion, plasma aldosterone, and serum sodium, potassium, calcium, and magnesium in children 11 +/- 1.5 years of age.

A total of 194 clinically healthy children 11 +/- 1.5 years of age were studied during different seasons. Systolic and diastolic blood pressure were determined by auscultatory endpoints, and blood and urine were collected at 4-hr intervals over a 24-hr span. Urinary norepinephrine, epinephrine, and dopamine were determined by HPLC, plasma aldosterone by RIA, serum sodium and potassium by ion-specific electrode, and calcium and magnesium by colorimetry. The circadian means showed statistically significant circannual variations in all variables except epinephrine. The highest circadian means of systolic and diastolic blood pressure and of urinary norepinephrine occurred during winter; the highest values of plasma aldosterone, serum potassium, and urinary dopamine were found in fall, those of serum calcium and magnesium during the summer, and that of serum sodium in spring. Circannual rhythms characterize functions related to blood pressure regulation in children. The circannual elevation of blood pressure (within the usual range) and of norepinephrine were both found to occur in winter. This time relation may have a functional significance, although a causal relationship is not proven by the temporal coincidence of two rhythms.