We report detailed characterizations of the effects of hot-electron stressing on low-frequency excess noise in commercial III-V nitride based heterojunction light-emitting diodes. The devices were stressed by applying a dc current ranging from 100 mA to 200 mA. Degradations in the device properties was investigated through detailed studies of the I-V characteristics, electroluminescence and flicker noise over a wide range of temperatures and biases. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. In particular, the voltage noise power spectral density increased by nearly three orders of magnitude. The temperature dependencies of the noise power spectra indicate that the noise arises from the thermal activation of carriers to localized states in the heterostructures, Our experiment shows that 1/f noise can be utilized as a sensitive tool for characterizing hot-electron degradation effects in III-V nitride heterojunctions.