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Background: Limited, outdated, and poor quality data are available on the prevalence of tinnitus, particularly in Italy. Methods: A face-to-face survey was conducted in 2014 on 2,952 individuals, who represented the Italian population aged 18 or more (50.6 million). Any tinnitus was defined as the presence of ringing or buzzing in the ears lasting for at least 5 min in the previous 12 months. Results: Any tinnitus was reported by 6.2% of Italian adults, chronic tinnitus (i.e. for more than 3 months) by 4.8%, and severe tinnitus (i.e. which constitutes a big or very big problem) by 1.2%. The corresponding estimates for the population aged ≥45 years were 8.7, 7.4 and 2.0%, respectively. Multivariable analysis on population aged ≥45 years revealed that old age (odds ratio (OR) = 4.49 for ≥75 vs. 45-54 years) and obesity (OR = 2.14 compared to normal weight) were directly related to any tinnitus, and high monthly family income (OR = 0.50) and moderate alcohol consumption (OR = 0.59 for <7 drinks/week vs. non-drinking) were inversely related. Conclusions: This is the first study on tinnitus prevalence among the general Italian adult population. It indicates that in Italy tinnitus affects more than 3 million adults and is felt as a major problem by more than 600,000 Italians, mostly aged 45 years or more.

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Hair cells, the mechanoreceptors of the acoustic and vestibular system, are presynaptic to primary afferent neurons of the eighth nerve and excite neural activity by the release of glutamate. In the present work, the role played by intracellular Ca2+ stores in afferent transmission was investigated, at the presynaptic level, by monitoring changes in the intracellular Ca2+ concentration ([Ca2+]i) in vestibular hair cells, and, at the postsynaptic level, by recording from single posterior canal afferent fibers. Application of 1-10 mm caffeine to hair cells potentiated Ca2+ responses evoked by depolarization at selected Ca2+ hot spots, and also induced a graded increase in cell membrane capacitance (DeltaCm), signaling exocytosis of the transmitter. Ca2+ signals evoked by caffeine peaked in a region located approximately 10 microm from the base of the hair cell. [Ca2+]i increases, similarly localized, were observed after 500 msec depolarizations, but not with 50 msec depolarizations, suggesting the occurrence of calcium-induced calcium release (CICR) from the same stores. Both Ca2+ and DeltaCm responses were inhibited after incubation with ryanodine (40 microm) for 8-10 min. Consistent with these results, afferent transmission was potentiated by caffeine and inhibited by ryanodine both at the level of action potentials and of miniature EPSPs (mEPSPs). Neither caffeine nor ryanodine affected the shape and amplitude of mEPSPs, indicating that both drugs acted at the presynaptic level. These results strongly suggest that endogenous modulators of the CICR process will affect afferent activity elicited by mechanical stimuli in the physiological frequency range.