LAUSR

Aging is associated with reductions in cardiovagal baroreflex sensitivity (cBRS), which increases cardiovascular disease risk. Preclinical data indicate that low testosterone reduces cBRS. We determined whether low testosterone is associated with reduced cBRS in healthy men. METHODS Twenty-six men categorized as young (N=6; age=31±4 years; testosterone=535±60 ng/dL), middle-aged/older with normal (N=10; aged 56±3 years; testosterone=493±85 ng/dL), or low (N=10; age=57±6 years; testosterone=262±31 ng/dL) testosterone underwent recordings of beat-by-beat blood pressure and R-R interval during rest and two Valsalva maneuvers, and measures of carotid artery compliance. IL-6, CRP, oxidized LDL cholesterol and TAS were measured. RESULTS Middle-aged/older men had lower cBRS compared to young men (17.0±6.5 ms/mmHg; p=0.028); middle-age/older men with low testosterone had lower cBRS (5.5±3.2 ms/mmHg; p=0.039) compared to age-matched men with normal testosterone (10.7±4.0 ms/mmHg). No differences existed among groups during Phase II of the Valsalva maneuver; middle-aged/older men with low testosterone had reduced cBRS (4.7±2.6 ms/mmHg) compared to both young (12.8±2.8ms/mmHg; p<0.001) and middle-aged/older men with normal testosterone (8.6±4.4ms/mmHg; p=0.046) during Phase IV of the Valsalva maneuver. There were no differences in oxidized LDL, (p=0.882) or TAS across groups (p=0.633). IL-6 was significantly higher in middle-aged/older men with low testosterone compared to the other groups (p<0.05 for all) and inversely correlated with cBRS (r=-0.594, p=0.007). Middle-aged/older men had reduced carotid artery compliance compared to young, regardless of testosterone status (p<0.001). CONCLUSIONS These observations indicate that low testosterone in middle-aged/older men may contribute to a reduction in cBRS; increased inflammation may also contribute to a reduction in cBRS.