Association between resting heart rate, VO(2)max and carotid intima-media thickness in middle-aged men

INTRODUCTION: Low resting heart rate (RHR) and high cardiorespiratory fitness (VO(2)max) are associated with a reduction in cardiovascular events (CV). Carotid intima-media thickness (CIMT) has been suggested as a predictor of CV. The purpose of this study was to investigate the association between RHR, VO(2)max and CIMT. METHODS: The subjects of this study were 707 males aged 40–50 who visited the National Health Center of South Korea, a health examination institution, from 2010 to 2016. RHR was measured using electrocardiogram. RHR was divided into 4 levels (<60 beats per minute; bpm, 60–69 bpm, 70–79 bpm, ≥80 bpm). VO(2)max was measured by grade exercise test. Subject's VO(2)max was divided into 3 levels (first, second and third tertiles). CIMT was measured by B-mode ultrasound. Carotid atherosclerosis was defined as CIMT >1 mm. RESULTS: There was no significant difference in CIMT according to RHR level and there was no correlation between RHR and CIMT. High and middle VO(2)max group had significant lower CIMT than low VO(2)max group (P < 0.001). There was also a correlation between VO(2)max and CIMT (R = −0.129, P < 0.001). The low VO(2)max group showed 3.56-fold (95% CI, 1.77–7.16) higher relative risk of carotid atherosclerosis than the high VO(2)max group. CONCLUSION: These results suggest that cardiovascular fitness index VO(2)max is associated to CIMT in middle-aged men. In addition, this study shows that VO(2)max are important indicators for the prevalence of carotid atherosclerosis.