1. A hearing aid system, comprising: a processor; and a memory, the memory storing instructions to cause the processor to perform: a cognitive state analysis circuit configured to analyze a cognitive state of a user; a context analysis circuit configured to analyze a context of the user; and an audio characteristic controller configured to control an audio characteristic of a hearing aid based on a joint assessment of a combined factor calculated by weighing together the cognitive state of the user and the context of the user, wherein the context of the user and the cognitive state of the user are independent of each other, and wherein the cognitive state includes at least one of: a cohort condition; and a cognitive level.