Metabolic Syndrome, Brachial Artery Diameter and Cardiorespiratory Fitness - The DR’s EXTRA Study

Abstract

The metabolic syndrome (MetS) is characterized by a systemic arterial remodeling which can be proved by a large brachial artery diameter (BAD). The arterial enlargement may result, however, also from long-term endurance-type physical activity (PA). PURPOSE: To study whether the association of a large BAD with prevalence of MetS can be further defined by allowing for the cardiorespiratory fitness as a proxy variable for long-term endurance-type PA. METHODS: The subjects were a population-based sample of 593 men and 583 women aged 57-78 years who participated in the DR’s EXTRA Study. Metabolic syndrome was determined by the NCEP criteria. The end-diastolic BAD was assessed by ultrasound and cardiorespiratory fitness as peak oxygen uptake (VO2peak) achieved in a maximal cycle ergometer exercise test. Age-adjusted linear regression analysis was used to compare the means of BAD in those with or without MetS. For the main analyses, sex-spesific tertiles of BAD and VO2peak were pooled in age-adjusted logistic regression analyses and the association was explored after the highest tertile of BAD (>4.25 mm in men, >3.36 mm in women) was further categorized according to tertiles of VO2peak (low ≤23.3 and high >28.9 ml/kg/min in men; low ≤18.4 and high >22.8 ml/kg/min in women). RESULTS: Mean BAD was higher in 323 (27%) subjects with MetS compared to those without MetS (3.80 vs. 3.63 mm, p<0.001 for difference between groups). Subjects (n=141) with a large BAD and a low VO2peak had an increased risk of having MetS (OR 5.1 [95% confidence interval, CI, 3.5-7.6], p<0.001) compared to subjects with narrower BAD (the two lowest tertiles). Additionally, 123 subjects with a large BAD but a high VO2peak had a decreased risk of having MetS (OR 0.4 [95% CI 0.2-0.8], p=0.004) compared to subjects with narrower BAD. The results were similar when assessed separately in men and women. CONCLUSION: The group with a large BAD includes subjects with unfavourable vascular risk factor profile judged by an increased risk of having MetS, but also subjects with a decreased risk of having MetS. These groups can be identified based on cardiorespiratory fitness. A large BAD should not be interpreted unambiguously as an unfavourable finding from viewpoint of vascular health without considering whether it may result from long-term endurance-type PA as well.