Hormone therapy is associated with preserved smooth muscle structure and dilation in the arterial vasculature of the leg in older women

Long-term hormone therapy (HT) is associated with reduced intima-medial thickness (IMT), an established risk factor for atherosclerotic disease, in the femoral artery of healthy older women relative to age-matched non-hormone users. However, the influence of continuous, long-term HT on the relation between age, IMT, and smooth muscle dilation has not been investigated in the popliteal artery, an artery prone to stiffening and calcification. In the present study, popliteal artery IMT and smooth muscle dilation (the increase in diameter to sublingual nitroglycerin, NTG) were assessed with Doppler ultrasound in young (Y: n = 16; age 23 ± 1 [mean ± S.E.M.]), older non-HT (O non-HT: n = 14; age 69 ± 1), and older HT (O HT: n = 8; age 67 ± 1) healthy women. The ∼0.5 mm increase in resting diameter observed in older non-HT women relative to young women was absent in older HT women, as was the age-related increase in IMT (Y: 0.52 ± 0.02 mm; O non-HT: 0.63 ± 0.02 mm; O HT: 0.56 ± 0.02 mm; p < 0.05 for age and hormone comparisons). NTG dilation (percent change above rest) was similarly attenuated in older non-HT women (Y: 8.6 ± 1%; O non-HT: 3.0 ± 0.7%; O HT: 7.4 ± 1.7%; p < 0.05 for age and hormone comparisons), and NTG dilation was inversely related to IMT (p < 0.01). Collectively, these results suggest that long-term, continuous HT may alleviate the detrimental effects of aging on both structural changes and smooth muscle dilation of the popliteal artery in healthy women.