Association of digital vascular function with cardiovascular risk factors: a population study

OBJECTIVES Vasodilation of the peripheral arteries during reactive hyperaemia depends in part on release of nitric oxide from endothelial cells. Previous studies mainly employed a fingertip tonometric device to derive pulse wave amplitude (PWA) and PWA hyperaemic changes. An alternative approach is based on photoplethysmography (PPG). We sought to evaluate the correlates of digital PPG PWA hyperaemic responses as a measure of peripheral vascular function. DESIGN The Flemish Study on Environment, Genes and Health Outcomes (FLEMENGHO) is a population-based cohort study. SETTING Respondents were examined at one centre in northern Belgium. PARTICIPANTS For this analysis, our sample consisted of 311 former participants (53.5% women; mean age 52.6 years; 43.1% hypertensive), who were examined from January 2010 until March 2012 (response rate 85.1%). PRIMARY OUTCOME MEASURES Using a fingertip PPG device, we measured digital PWA at baseline and at 30 s intervals for 4 min during reactive hyperaemia induced by a 5 min forearm cuff occlusion. We performed stepwise regression to identify correlates of the hyperaemic response ratio for each 30 s interval after cuff deflation. RESULTS The maximal hyperaemic response was detected in the 30-60 s interval. The explained variance for the PPG PWA ratio ranged from 9.7% at 0-30 s interval to 22.5% at 60-90 s time interval. The hyperaemic response at each 30 s interval was significantly higher in women compared with men (p≤0.001). The PPG PWA changes at 0-90 s intervals decreased with current smoking (p≤0.0007) and at 0-240 s intervals decreased with higher body mass index (p≤0.035). These associations with sex, current smoking and body mass index were mutually independent. CONCLUSIONS Our study is the first to implement the new PPG technique to measure digital PWA hyperaemic changes in a general population. Hyperaemic response, as measured by PPG, is inversely associated with traditional cardiovascular risk factors such as male sex, smoking and obesity.