According to an answer to the question Why is the shutter not closed by default on mirrorless cameras, while it is closed on film cameras? mirrorless cameras have a shutter "open by default".
In addition, the mirrorless cameras obviously have no mirror.
Thus, when changing the lens, a mirrorless camera has a fully exposed sensor. On the other hand, a digital SLR has a closed shutter and a mirror in front of the sensor.
Do these properties make mirrorless cameras more sensitive to sensor dust?