The energy hole problem is caused by earlier turning off of sensor nodes nearer the sink due to more frequent data transmission, particularly in asynchronous MAC-based Wireless Sensor Networks (WSNs). To resolve this issue, this letter proposes an Energy-aware Hybrid Data Aggregation Mechanism (EHDAM) that is designed to adaptively control the number of data transmission with burst length based and time-out based transmissions. Especially, EHDAM adjusts the burst length threshold value in reciprocal proportion to the remaining energy state of the node so that reducing the number of data transmission; hence, EHDAM extends lifetimes of the nodes affected by the energy hole problem.