Normative data and the influence of age and gender on microcirculatory function in a middle-aged cohort: Results from the SCAPIS study.

The objective of this study was to assess normative values for comprehensive forearm skin microcirculatory function: oxygen saturation, tissue fraction of red blood cells (RBCs) and speed resolved perfusion. Furthermore, to examine the influence of age and gender on microcirculatory function. Measurements were performed using a non-invasive probe-based system, including diffuse reflectance spectroscopy and laser Doppler flowmetry, yielding output data in absolute units. The study was conducted within the Swedish CArdioPulmonary BioImage Study (SCAPIS) and included 1765 men and women aged 50-65 years from the Linköping general population. Normative values are given at baseline, at the end of a 5-min occlusion of the brachial artery and during hyperemia after occlusion release. We found a consistent age distribution where the oldest individuals had the lowest peak oxygen saturation (p<0.001) and the highest baseline low-speed perfusion (p<0.001). Women had higher peak oxygen saturation (p<0.001), lower RBC tissue fraction in general (p<0.001), lower baseline perfusion in all speed regions (p=0.01) and lower peak high-speed perfusion at hyperemia (p<0.001). The normative data can be used as reference values in future studies of disease-specific populations. The results show that age and gender are important aspects to consider in studies of microvascular function. Women and younger age were associated with higher peak oxygen saturation after ischemia. This is a novel parameter indicating overall microcirculatory function associated with vascular dilatation capacity.