Gender-Selective Interaction Between Aging, Blood Pressure, and Sympathetic Nerve Activity

Abstract

Abstract-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 (PϽ0.01 and PϽ0.001, 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. (Hypertension. 2005;45:522-525.)Key Words: age Ⅲ cardiovascular diseases Ⅲ gender Ⅲ heart rate Ⅲ hypertension Ⅲ sympathetic nervous system A lthough cardiovascular risk increases with age in both sexes, this increase is sharper in women. 1-3 More women than men have congestive heart failure and, overall, more women than men die from cardiovascular disease in the US. 1 This gap continues to widen. The mechanisms underlying this differential age effect are not well understood. Changes in serum total cholesterol level, body mass index, and diabetes prevalence explain only 50% of the age-related increase in cardiovascular morbidity and mortality among women. 4 Thus, other factors are implicated in the high prevalence of cardiovascular disease in older women.The sympathetic nervous system contributes importantly to cardiovascular disease manifestations. 5,6 It is generally accepted that sympathetic activity increases progressively with aging. 7,8 However, little is known of the effects of gender on age-related changes in sympathetic traffic, and the existing evidence is conflicting. 9,10 We measured sympathetic traffic, blood pressure, and heart rate in a large sample of normal white subjects. We tested the hypothesis that aging has a greater impact on sympathetic traffic in women than in men. Furthermore, we evaluated the relative influence of age versus menopause per se on sympathetic activity, and we examined whether there is any gender differential in the interaction between sympathetic traffic and blood pressure. Methods SubjectsWe studied 216 normal white subjects (120 males and 96 females). Mean age was 39.1 years (range, 20 to 72 years) for males, and 40.1 years (range, 20 to 71 years) for females. Body mass index was similar in t...

Muscle sympathetic nerve activity during cold stress and isometric exercise in healthy older adults

“…To this end, the present investigation examined sympathetic nervous system activation in healthy young and older adults using a standardized whole body skin surface cooling protocol via water-perfused suit (3,30,51,55). Consistent with a wide body of literature examining MSNA at rest in older adults at thermoneutrality (27,39,53), older adults in the present study exhibited increases in basal muscle sympathetic outflow. Furthermore, whole body cold stress elicited pronounced increases in MSNA burst frequency and strength in older, but not young, adults.…”

“…MSNA and plasma norepinephrine concentrations are elevated with advancing age (15,24,27,39,53); therefore, impairments in norepinephrine-mediated vasoconstriction have generally been attributed to sustained agonist-mediated desensitization in ␣-adrenergic receptor responsiveness (24). Conversely, the age-related increase in MSNA during cooling may be a compensatory response as a result of age-associated reductions in ␣-adrenergic receptor responsiveness.…”

The effect of gender on the sympathetic nerve hyperactivity of essential hypertension

“…Thus, individual patients of the groups were Caucasians and were examined using the same protocol, under similar laboratory conditions, while avoiding the influence of age, dietary intake, body weight, large meal or visceral distension factors, which are known to affect sympathetic activity or its control. 14,15,17,19,[30][31][32][33][34] We also quantified the mean frequency of s-MSNA units and that of MSNA multiunits. The former was considered as an index of the mean frequency of efferent sympathetic nerve …”

“…4,14 On the other hand, previously reported findings in normotensive populations have not been consistent as to whether MSNA levels are different between men and women. Young women may have a lower [15][16][17][18][19] or similar 20,21 level of resting MSNA relative to young men. Also, older women may have a lower 15 or similar 17,19 level of resting MSNA relative to older men.…”

Is Gender a Factor in the Reduction of Cardiovascular Risks With Exercise Training?

“…42-45 Also, older women have closer linkage between sympathetic nervous activity and BP than older men, and have exaggerated sympathetic nervous activity compared to their male counterparts. 43- 45 On the other hand, a previous study demonstrated that a 12-week exercise training program improved both the sympathetic and parasympathetic nervous activity in obese individuals. 46 In our study, it is possible that exercise training more greatly improved the exaggerated autonomic nervous activity in older females, and consequently led to their greater reduction of BP.…”