Gender difference in age-related changes in vascular function.

PURPOSE: We investigated whether, in a randomly selected population of 55-year-old men and women, there is a relationship between vascular function measured as flow-mediated (endothelium-dependent) and nitroglycerine-mediated (nonendothelium-dependent) dilatation of the brachial artery and conventional risk factors for cardiovascular disease such as gender, smoking, elevated blood-lipids and high blood pressure. The results are compared with those in a young healthy population of 35-year-olds.
SUBJECTS: A total of 57 men (73% of the invited males) living in the community and 47 women (62% of the invited females) participated and were compared with a previously studied 35-year-old population (52 men and 56 women).
METHODS: Basal brachial artery diameter was measured by high-frequency ultrasound methods. Endothelial function was measured as flow-mediated dilatation (FMD) in response to reactive hyperaemia. The nonendothelium-dependent vasodilatation was measured after administering sublingual nitroglycerine (NTG).
RESULTS: Flow-mediated endothelium-dependent dilatation was similar in men and women being 3.1 +/- 2.5% (mean +/- SD) in men vs. 2.6 +/- 2.3% in women. FMD of the brachial artery was negatively correlated with vessel size in both men and women (P < 0.001). Men had larger brachial artery diameter than women (4.6 +/- 0.7 vs. 3.6 +/- 0.4 mm, P < 0.001). There was no difference in FMD or in NTG-induced dilatation in the women receiving oral oestrogen replacement therapy compared with those that did not. The women taking oral oestrogen had lower cholesterol than those not taking oral oestrogen (P=0.04). FMD was not correlated with any of the risk factors. NTG-induced vasodilatation was correlated with the body mass index (BMI) in men (P=0.01) and a combined risk factor score in women (P=0.04). There was a large increase in the number of subjects with cardiovascular risk factors in the 55-year-old men and women compared with the 35-year-olds. The distribution of risk factors was fairly equal amongst men and women.
CONCLUSION: There are no correlations between any of the conventional cardiovascular risk factors and FMD in a population of 55-year-olds, but there is a high prevalence of risk factors in the 55-year-old age group. NTG-induced vasodilatation correlated with the BMI in men and a combined risk-factor score in women. FMD-induced vasodilatation is smaller in women at 55 years of age than at 35 years of age. FMD was similar in men at 35 and 55 years of age and in men and women at 55 years of age. The smaller FMD in women at 55 years of age, compared with at 35, could be due to postmenopausal hormonal changes.