Short- and long-term changes in auditory sensitivity and tinnitus distress between acute and chronic tinnitus: Longitudinal observation in a community-based sample

Chronic tinnitus is a common consequence of hearing loss, which commonly coexists with a degree of increased subjective sensitivity to sound intensity, and sometimes overt hyperacusis. Central gain is thought to be an underlying mechanism for hyperacusis, whilst its relationship with tinnitus is debated. The natural history of chronic tinnitus from its acute stages has been subject to very limited formal study, and only from within the sub-population attending specialist clinics. We studied community-based samples of individuals with Acute Tinnitus (AT: <6 weeks from onset, N = 51), who were followed up longitudinally 6 months post-onset (N = 26), those with Chronic Tinnitus (CT: >6 months from onset, N = 51), and Non-Tinnitus controls (NT: N = 35) age/sex/hearing matched to the Acute Tinnitus group. We measured tinnitus symptoms with loudness matching, numerical rating scales (NRS), and the Tinnitus Handicap Inventory (THI) and Tinnitus Functional Index (TFI) questionnaires, and subjective auditory sensitivity with categorical loudness scaling (CLS) and the Hyperacusis Questionnaire (HQ) and Inventory of Hyperacusis Symptoms (IHS). Results revealed that measures of tinnitus (psychoacoustically matched loudness, THI, TFI) were maximal around the time of onset and reduced significantly over initial months, in line with previous reports of specialist clinic-based cohorts without high levels of initial distress, but with the additional novel demonstration of a reduction in psychoacoustically matched tinnitus loudness. Conversely, measures of auditory sensitivity (HQ, IHS, CLS slope at 1 kHz and at tinnitus frequency) did not change longitudinally or differ between AT and NT groups. We interpret these changes as indicating spontaneous habituation to the tinnitus over time, but also that subjective auditory sensitivity is not necessarily directly linked to tinnitus symptoms.