An implantable stimulator includes a housing configured to be implanted beneath a skin surface of a patient and having a first surface adapted to face inwardly into tissue of the patient at or near a target tissue location； pulse generation circuitry located within the housing and electrically coupled to at least two electrodes, the pulse generation circuitry being adapted to deliver stimulation sessions by way of the at least two electrodes to the target tissue location, wherein each stimulation session included in the stimulation sessions has a duration of T3 minutes and a rate of occurrence of once every T4 minutes, wherein a ratio of T3 to T4 is no greater than 0.05； and a primary battery contained within the housing and electrically coupled to the pulse generation circuitry, the primary battery having an internal impedance greater than 5 ohms.
