Vedel-Krogh S, Rasmussen KL, Nordestgaard BG, et al. - Whether high plasma complement C3 level is related to high risk of asthma hospitalisations and exacerbations was investigated in this study. In 101,029 persons from the Copenhagen General Population Study, experts prospectively evaluated the risk of asthma hospitalisations. They also evaluated asthma exacerbation risk in 2,248 people with allergic asthma. According to the findings, in correlation with high level of plasma complement C3, there was a high risk of asthma hospitalisations in the general population and a high risk of asthma exacerbations in people with allergic asthma. A causal role of the complement system in asthma severity was supported by these data.