Impact of age and gender on microvascular function Oliver Schlager * , Aura Giurgea * , Alexandra Hammer * , Silvia Charwat-Resl * , Christian Margeta * , Markus Mueller * , Teresa Ehringer * , Sonja Zehetmayer † , Andrea Willfort-Ehringer * , Renate Koppensteiner * and Michael E. Gschwandtner * * Division of Angiology, Department of Medicine II, Medical University of Vienna, Vienna, Austria, † Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria ABSTRACT Background Microcirculatory function can be assessed by postocclusive reactive hyperaemia (PORH) using laser Doppler fluxmetry. Previous studies have shown that PORH reveals microvascular damage at an early stage. In particular, at younger ages, PORH might depend on age and gender. To implement PORH into a larger scale of clinical studies, one has to be aware of the influence of age and gender on microcirculation. The aim of this study was to assess the impact of age and gender on microcirculatory function during adolescence. Materials and methods Within the scope of an epidemiological project, 896 children and adolescents under- went assessment of PORH by laser Doppler fluxmetry. Microcirculatory parameters during PORH (baseline perfusion, biological zero, peak perfusion, time to peak perfusion and recovery time) were analysed in relation to age (by tertiles) and gender. Results Baseline perfusion, biological zero and peak perfusion were lower in children/adolescents in the upper age tertile (123–181 years) than in the middle (98–122 years) and lower (43–97 years) age tertiles (P < 00001). In the total of participants, baseline perfusion, biological zero and peak perfusion were higher in males than in females (P < 00001). Analysing microcirculatory parameters as a function of age and gender, the sex differences were only apparent in the upper and the middle age tertiles, but not in the lower. Conclusions During adolescence, PORH is a function of age. At higher age, microvascular reactivity consid- erably depends on gender, whereas no sex differences are present at younger ages. Keywords Endothelial function, epidemiology, laser Doppler, microcirculation, microvascular reactivity. Eur J Clin Invest 2014; 44 (8): 766–774 Introduction To assess microvascular function, postocclusive reactive hy- peraemia (PORH) measured by laser Doppler fluxmetry has been established as easily accessible, noninvasive diagnostic test [1,2]. Several studies have shown that PORH – as measured by laser Doppler fluxmetry – reveals early impairments of microvascular reactivity that can often be attributed to meta- bolic disorders and may also mirror generalized systemic microvascular dysfunction [3–7]. Premature alterations of microvascular PORH can even be detected in children and adolescents with metabolic disorders [5–7]. To prospectively introduce microvascular PORH into a larger scale of clinical studies and to consider its implementation into clinical practice, one has to be aware of changes in microvas- cular reactivity during physical development. Physical growth is associated with the growth of microvascular networks and an increase of microvascular wall mass [8,9]. Such structural changes jointly occur with changes in microvascular perfusion pressure and microvascular blood flow [10]. As a consequence, tissue metabolic requirements may change during juvenile growth subsequently affecting microvascular autoregulation. In addition to growth-related changes – especially in later adoles- cence – gender might further influence microvascular reactivity. Experimental data have linked juvenile growth with changes in endothelial function and reactivity of arteriolar smooth muscle cells [11,12]. Referring to epidemiological data, previous studies in elderly people suggested impairments of microvas- cular reactivity upon ageing [13,14]. Notably, the biology of ageing has to be differentiated from the physiological processes during juvenile growth. Therefore, it is still unclear whether and to which extent juvenile growth has an impact on micro- vascular function. Hence, the aim of the present study was to assess the impact of gender and age on microvascular PORH measured by laser Doppler fluxmetry in an adolescent population. 766 ª 2014 Stichting European Society for Clinical Investigation Journal Foundation DOI: 10.1111/eci.12293 ORIGINAL ARTICLE