Medical body area networks (MBAN) impose several requirements to the medium access control layer which have various contexts: energy efficiency, QoS providing, reliability. And a cognitive radio (CR) network should be able to sense its environment and adapt communication to utilize the unused licensed spectrum without interfering with licensed users. As CR nodes need to hop from channel to channel to make the most use of the spectrum opportunities, we consider asynchronous medium access control (MAC) protocols to be solution for these networks. The DCAA-MAC protocol presented in this paper has been designed has been designed specifically for wireless body area network with cognitive radio capability. The DCAA-MAC protocol has energy-efficiency, low latency, and no synchronization overhead by provide asynchronous and fast channel switching. Analytical models are shown to perform at low energy consumption, to scale well with network size.