Can the Determination of Salivary Cotinine Level Be a New Method in Diagnosis and Follow-up of Childhood Tinnitus?

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Background: There are many risk factors for childhood tinnitus such as hearing loss, exposure to high pitch sound, and passive smoking. Cotinine (C) is one of the metabolites of nicotine and is an important biochemical marker that reveals the objective and numerical indication of smoking exposure. Although there is a study investigating the role of urinary C levels in the etiology of tinnitus (T), the role of salivary C levels has not yet been elucidated. Objectives: Therefore, this study aimed to investigate the risk factors of idiopathic subjective T in children in terms of passive smoking and whether the salivary C level can be used as a novel marker for monitoring and follow-up of T. Methods: We retrospectively studied 1,245 children aged 7 - 15 years with T. We excluded 830 patients (66.5%) whose total tinnitus diagnosis was confirmed due to organic causes such as middle ear pathology and hearing loss. The remaining 415 (33.5%) patients with subjective T and 200 healthy individuals constituted the study and control groups. Complete blood counts, routine biochemical tests, and salivary C levels of children with T and controls were measured and their parents were also evaluated. Results: In univariate analysis, parents’ C, children’s C, ALP, and erythrocyte levels were significantly associated with T (P < 0.001 in all). Regarding laboratory values, erythrocyte and serum ALP levels were significantly associated with T (P < 0.001 in both) in univariate analysis (OR, 0.99; 95% CI, 0.98 to 0.99 for erythrocyte and OR, 157.04; 95% CI, 44.7 to 551.6 for serum ALP level). No significant relationships were found between other parameters. These four parameters that were found to be significant in the univariate analysis showed meaningful associations with T in multivariate analysis (P < 0.01 for parents C and P < 0.001 for other parameters). It was also observed that as the C levels increased in the parents, the C level also increased in children. Conclusions: There is a significant correlation between salivary C levels and parental salivary C levels in children. This suggests that the salivary C be used for evaluating the etiology of T in children and monitoring children with T exposed to cigarette smoke.