Gender-selective interaction between aging, blood pressure, and sympathetic nerve activity.

The mechanisms mediating the more striking age related increase in cardiovascular disease in women than in men are poorly understood. We tested the hypothesis that aging has a greater impact on sympathetic traffic in women than in men. Muscle sympathetic nerve activity (MSNA), blood pressure, and heart rate were measured in 120 healthy males and 96 healthy females aged 20 to 72 years. MSNA increased with age in both sexes, but age explained 53% of MSNA variance in female subjects and only 8% of MSNA variance in male subjects. Both the slope and intercept of the regression lines were significantly different between male and female groups (P<0.01 and P<0.001, respectively). For each decade of life, women showed an increase of 6.5 bursts/min in comparison to an increase of 2.6 bursts/min in males. Menopause did not explain the age-related increase in sympathetic traffic. For every 10-burst/min increment in MSNA in subjects older than 40, mean blood pressure increased by 2.7 mm Hg in men and by 6.1 mm Hg in women. Aging is accompanied by a greater increase in sympathetic traffic in women than in men, independent of menopausal status. Sympathetic neural mechanisms may contribute importantly to the more marked influence of age on blood pressure and cardiovascular disease in women.