Influence of sex and age on serum nitrite/nitrate concentration in healthy subjects

Abstract

Measurement of serum nitrite/nitrate (NO x) concentrations has been considered useful to estimate nitric oxide production in humans. However little is known about the physiologic range and the factors affecting serum NO x levels. The aim of this study was, thus, to investigate the influence of sex and age on serum NO x levels in healthy subjects. We selected 263 healthy subjects (118 women and 145 men, 20–69 y) from 505 consecutive subjects who received annual medical checkups at our hospital. Serum NO x levels were determined using an analyzer employing the Griess method. The linear regression analysis showed that NO x increased significantly according to age in women ( r=0.22, P<0.05), but did not in men ( P=NS). Women of the younger age group (<40 y) showed significantly lower NO x levels than men of the same age group ( P<0.05), whereas there was no significant difference between men and women of the older age (≥40 y). Then, to investigate whether menopause affects serum NO x levels, middle aged women (46–55 y) were selected. Multiple logistic regression analysis showed that menopause was an independent factor for increased serum NO x levels in middle aged women ( r=0.4, P<0.05). These results suggest that the serum NO x concentration is affected by age in healthy women, possibly depending on menopausal state.